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Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
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EFFECTS OF ANESTHESIA ON
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INTERMEDIARY METABOLISM Edward A. Brunner, MD., PhD., S. C Cheng, PhD., and M L. Berman, MD., PhD. Department of Anesthesia, Northwestern University Medical School, Chicago, Illinois
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INTRODUCTION Some order is beginning to emerge from the confusion concerning metabolic effects of anesthetics which Bunker noted only a dozen years ago ( 1). Early clinical observa tions, many lacking in scientific merit, have given way to well designed and executed studies focusing on specific problems. Most reports have been directed to carbohy drate or energy metabolism in the intact organism, liver, or central nervous system. Prior reviews of interest have appeared (I-B).
CARBOHYDRATE METABOLISM Carbohydrate homeostasis reflects the balance of a complex set of interactions including intestinal absorption, peripheral substrate utilization, the effects of endo crine factors (insulin, glucagon, steroids, growth hormone), gluconeogenesis, glycogenolysis in liver and muscle, lipolysis, and renal clearance of glucose. Anes thetics affect all of these. Systemic Manifestations
Reynoso first observed glycosuria after ether anesthesia in 1853 ( 14). Most anesthet ics, with the possible exceptions of enflurane and methoxyflurane, are associated with hyperglycemia but not with a rise in plasma insulin level ( 15). The ratio of plasma insulin/plasma glucose falls ( 16), indicating that certain anesthetics may partially inhibit insulin release from the pancreas. This is best substantiated for halothane. The role of sympathetic inhibition in this anesthetic depression of insulin secretion has yet to be fully explored, although one observation ( 17) reports that phentolamine did not prevent the failure of insulin response to infused glucose during halothane anesthesia. 391
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Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
Skeletal Muscle Theye and his co-workers attempted to define the organ site of the decrease in whole body oxygen consumption which accompanies general anesthesia ( 18). They showed that oxygen consumption of in situ canine gracilis and gastrocnemius muscles, two markedly dissimilar muscles, decrease equally with increase in halothane concentra tion ( 19, 20). This justifies proportional extrapolation to all skeletal muscle, which accounts for 30 to 40% of total body oxygen consumption. Both halothane and methoxyflurane (21) at ciinical concentrations inhibit state 3 (ADP present) respira tion of rat skeletal muscle mitochondria with glutamate as substrate, but not with succinate. State 4 respiration (ADP absent) with both glutamate and succinate is virtually unalfected. These anesthetics block electron transport in skeletal muscle as they do in brain and liver (see below), and thus reduce oxygen consumption and heat production generated by normal muscle activity. The syndrome of malignant hyperpyrexia has been the subject of a recent symposium (22). In isolated rat hemidiaphragm (23) ether depresses glucose uptake but does not block insulin stimulation of glucose uptake. It increases lactate formation from glycogen; in the presence of insulin lactate formation is doubled. Normally; hemidia phragm converts to glycogen 70% of the increased glucose uptake due to insulin. In the presence of ether only 50% is converted to glycogen, the remainder appearing
as lactate.
Liver Jowett & Quastel (24) reported that rat liver respiration was not alfected by diethyl ether. More recent studies (25, 26) demonstrate that halothane produces a dose related reversible depression of oxygen consumption and an increase in glycolysis by rat liver slices. Fink (27), using cultured mouse heteroploid cells, showed that methoxyflurane, halothane, chloroform, and diethyl ether depress oxygen uptake and increase glycolytic rate in order of potency related to the hypnotic activity of the drug. One study (28) of liver slices from anesthetized dogs failed to show changes, probably because of loss of volatile anesthetics from the tissue prior to measurement. Isolated perfused bovine (29), canine (30), and rat liver (31) have been employed to study anesthetic elfects on metabolism. With dog liver, 2% chloroform and 1 % methoxyflurane caused glucose release, increased lactate/pyruvate ratio, and loss of potassium and cellular enzymes from the liver. Halothane produced no measurable alterations. In bovine and rat liver chloroform, diethyl ether, halothane, and me thoxyflurane (where studied) cause depression of oxygen consumption, lactate utili zation, gluconeogenesis, and glycogen synthesis but stimulate release of glucose or lactate into the perfusate. Urea synthesis is depressed and cellular integrity as measured by loss of cellular enzymes and potassium is altered reversibly by chloro form and high concentrations of ether. In fed rats there is a marked decrease in tissue content of both 2-oxoglutarate and citrate and a decrease in calculated NAD/NADH ratio for both cytoplasmic and mitochondrial couples. These findings are consistent with stimulation of glycogenolysis and glycolysis and inhibition of gluconeogenesis and oxidative metabolism. The lack of inhibition of fatty acid
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
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oxidation (32) and the decrease in NAD/NADH ratios lead to the speculation of anesthetic inhibition in the region of NADH dehydrogenase as a major site of anesthetic action (33). In vivo studies of liver utilizing freeze-clamping techniques (34) show that halo thane, methoxyflurane, trichloroethylene, and diethyl ether all cause elevated blood and tissue glucose levels and depletion of liver glycogen. In contrast to in vitro studies, halothane caused no lactate accumulation in the liver in vivo. Lactate/pyru vate ratios remain normal even when lactate levels rise, as with trichloroethylene and diethyl ether anesthesia. With halothane, decreases in liver ATP and shift of cytoplasmic and mitochondrial redox couples to a more reduced state do not occur in the intact, as they do in the perfused, liver. Decreases in the liver 2-oxoglutarate levels occur but are less severe (20% of normal in vivo, 50% in vitro) and are accompanied by parallel alterations of glutamate, indicating the presence of intact control mechanisms not functional in the isolated perfused preparation. Attempts to precisely characterize the basic cellular actions of narcotics have led to demonstrations, first, that urethane and certain alcohols produce a metabolic block of electron transfer (35) and later, that amobarbital and other barbiturates inhibit mitochondrial oxidation of pyruvate and fumarate, but not of succinate (36). This amobarbital inhibition was later extended to all NAD-linked mitochondrial oxidations (37). Cohen and co-workers have shown that halothane in concentrations up to 2% (38-40) reversibly blocks NAD-linked substrate oxidation but does not block succinate oxidation. Only amobarbital-sensitive but not amobarbital-insensi tive oxidations are blocked. The site of halothane inhibition occurs in the region of Complex I between NADH dehydrogenase and coenzyme Q (Figure 1), at or near the site(s) of the inhibiting action of rotenone and amobarbital (4 1 -43). NAD-Linked Substrate
Succinate
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In
Is
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Non-heme Iron----::)(�--I CoQ Figure I.
-
Cytochrome Chain
-
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S ite of anesthetic inhibition of electron transport.
Methoxyflurane, diethyl ether, enflurane, forane, fluroxene, trichloroethylene, and chloroform in anesthetic concentrations subsequently have been shown to demonstrate a dose-dependent reversible inhibition of electron transport in a way similar to halothane. The concentrations of six anesthetics necessary for 50% inhibi tion of state 3 respiration bears an inverse log-log relationship to their lipid solubility (44). Potency as electron transport inhibitor in vitro is directly related to anesthetic potency in vivo. Miller & Hunter (45) suggest that errors in experimental design in some studies have caused inadvertent mitochondrial damage due to exposure to excessive concen trations of halothane and have led to the erroneous conclusion that halothane is a
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
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true uncoupling agent. By contrast, studies of mitochondrial calcium transport (45) in which halothane exposure is carefully controlled show that concentrations as high as 4% do not alter the final steady state of calcium accumulation as would a true uncoupler. Moreover, the response of rapid calcium release on addition of a true uncoupler remains intact, indicating that halothane acts differently than a true uncoupler. There is evidence that methoxyflurane and diethyl ether (41) at anesthetic concen tration, and others at higher concentrations (46), have additional actions on mito chondrial function, including inhibition of succinate oxidation, some degree of uncoupling, loss of respiratory control, and alteration of the mitochondrial mem brane (46-50). The possibility that anesthetics alter membrane permeability and thereby affect metabolic function by altering the delivery of substrate to the site of utilization has been suggested (4 1), based on data observed in rat atria and human red cells as well as in mitochondria. Further implications of the above cited findings have yet to be fully evaluated.
Central Nervous System Metabolism in the nervous system subserves three main functions: 1: to maintain structural integrity, 2. to maintain ionic and electrical gradients across excitable membranes, and 3. to synthesize neurotransmitters. The major metabolic effects of anesthetics relate to the latter two. The following discussion will address effects of volatile anesthetics on energy metabolism, on incorporation and turnover of tracer compounds, and on neurotransmitters. The effect of volatile anesthetics on the respiration of intact brain in vivo is uniformly inhibitory (5 1-53). The exact extent of this inhibi tion varies for different agents and species. Several factors (Poz, Pcoz, blood pres sure, vascular resistance, temperature, the anesthetic agent employed, and cerebral blood flow) are important in determining the degree of respiratory inhibition ( 13, 53). With brain slices, anesthetic agents reduce the additional increment of oxygen utilization due to stimulation by electrical current or high potassium concentration before the resting respiration is altered. The concentration of anesthetic agent required in vitro is usually higher than that in vivo (9). With few exceptions, anesthetic agents depress oxygen consumption by cerebral cortex slices, by chopped brain suspensions, and by brain homogenates (9, 12, 54, 55). Volatile anesthetic agents cause varied changes in lactate content and glycolysis in the in vivo brain, in slices, and in homogenates (5, 9, 54--59). The recent data demonstrating decreased lactate in brain material recovered with a "brain blower" deserve special mention. Total tissue high energy phosphate content is not altered by volatile anesthetic agents (9, 56, 58-6 1). Glucose and glycogen can be added to the high energy reserve to represent total energy stores. These increase as metabolic rate is depressed by anesthetics (56-58). ENERGY METABOLISM
MITOCHONDRIAL AND SYNAPTOSOMAL METABOLISM Crude brain mito chondria can be separated into several subfractions, including synaptosomes and heavy mitochondria. The respiration and oxidative phosphorylation of crude mito-
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chondria supported by pyruvate, glutamate, or 2-oxoglutarate are inhibited by halothane and methoxyflurane but not by nitrous oxide, diethyl ether, chloroform, or cyclopropane (62). Presumably, halothane uncouples oxidative phosphorylation of this crude preparation (63). This idea of "uncoupling," put forth in the early fifties (64), is supported by more recent work using purified mitochondria from rabbit brain and high concentrations of halothane (65), but disputed by work using rat brain mitochondria (66). This latter report demonstrates that halothane inhibits ADP-stimulated respiration of mitochondria metabolizing glutamate. This inhibit ing effect is virtually absent with succinate. Calcium uptake is also found to be inhibited by halothane. These results have been confirmed in a concurrent study using both mitochondrial and synaptosomal preparations (67). The succinate rever sal of anesthetic-inhibited respiration was first observed many years ago (55, 68) without adequate explanation. It appears likely that further studies will confirm an anesthetic sensitive site in electron transport similar to that already identified in liver mitochondria. The validity of results based on the cerebral metabolism of labeled substrates is often in question due to the large cerebral blood flow which introduces a "contaminating" effect from metabolism of other body tissues. This compounds difficulties caused by the postmortem changes which are well known in neurochemistry. Anesthetic agents alter amino acid labeling in the brain and spinal cord. In general (56-58, 60, 69-74), the incorporation of glucose carbon into aspar tate, glutamate, glutamine, and y-aminobutyrate is reduced but similar incorpora tion into alanine is variable, Glutamate content is unchanged or decreased. Incorporation of carbons from acetate, butyrate, and citrate is not affected. These differences observed in the incorporation of labeled carbon from different substrates can be interpreted by the concept of metabolic compartmentation (75). Two groups of substrates are known to be metabolized by different compartments and their correlated anatomic entities have been respectively assigned to nerve endings and glia. The anesthetic agents appear to inhibit primarily the glucose utilizing compart ment, i.e. the nerve endings (69). TRACER EXPERIMENTS
NEUROTRANSMITTERS This section includes data on the effect of amobarbital, chloralose, allobarbital, hydroxydione, methylpentyol, pentobarbital, thiopental, phenobarbital, and the volatile anesthetics on synthesis, degradation, release, up take, and other mechanisms of removal from site(s) of action of neurotransmitters. Most inhibit the synthesis of acetylcholine (ACh) ( 1 2, 68, 69, 76-78) and cause increased ACh content in vivo (8, 79, 80), which is attributed to nonutilization. In contrast, the ACh content of slices exposed to halothane is lower than that of controls and its synthesis from acetate is not altered (69). The release of ACh is reduced by anesthetic agents (1 1 , 76, 8 1 ) and its turnover rate is decreased (69, 78). Anesthetic agents cause reduced synthesis of y-aminobutyrate (GABA) in rat cortex slices (69); release is not affected (81). In stimulated slices barbital causes increased GABA release (82). GABA content in rat brain varied (83, 84) and GABA uptake by rat cortex slices also varied (69, 82, 85).
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Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
The primary manner of the removal of GABA from synaptic areas is by re-uptake by cells near the synapses followed by enzymatic degradation via the GABA shunt, a unique metabolic pathway in the brain. A glial function for such removal has been advanced. This whole matter concerning GABA requires further clarification. HYPOTHESIS OF ANESTHETIC ACTION The increase in energy stores, the re duced metabolic rate (oxygen consumption), and the reduced incorporation of glucose carbon into intermediate metabolites suggest a decreased utilization of energy in brain during anesthesia. Earlier theories based on the inhibition of energy production as the primary cause of anesthesia failed when the energy stores were found not to decrease and the reduction of cerebral NAD could not be demonstrated (59, 86). In vivo inhibition of synaptic transmission was found to precede axonal block by anesthetic agents, suggesting that neurotransmitters may play a crucial role in anesthesia mechanisms. Two lines of thought have been proposed. One suggests that the increased cytoplasmic calcium concentration, induced by impaired mito chondrial uptake of calcium under influence of anesthetic agents, may cause reduced sensitivity to excitation by ACh (66, 67). This idea requires no participation of an inhibitory synapse which some physiological experiments have suggested. The other theory postulates that degradation of GABA is retarded by anesthetic block of Complex I. This causes a rise in synaptic GABA content followed by synaptic inhibition. Regardless of the cause of the decreased synaptic activity, the outward manifestation would be anesthesia. A decrease in synaptic work requires less utiliza tion of energy for ionic transport. Extra energy is shifted to the synthesis of energy rich compounds such as glycogen, lipids, and glutamine. The energy-producing reactions (respiration and glycolysis) are somewhat reduced. This oversimplified hypothesis is attractive. It agrees with most neurochemical findings. The details are more difficult to formulate. For example, glial functions, which are just being investigated, may contribute heavily in the overall mechanism of anesthesia.
Miscellaneous The effects of inhalation anesthetics on myocardial metabolism have been included in a recent review of Merin (87) and interested readers are referred thereto. Isolated studies of anesthetic effects on lung and kidney metabolism and of adrenal enzyme activity have been reported. A few isolated studies of anesthetic effect on specific enzymes have also been reported, but systematic analysis of results is not yet possible.
FAT METABOLISM Studies of anesthetic effects on lipid metabolism in man have focused on the changes in the plasma levels of nonesterified fatty acids (NEFA). In most studies adequate control of pertinent parameters is lacking or not recorded. Pre-anesthetic emotional stress and surgical stress are more significant than nitrous oxide-halothane anes thesia in causing a marked rise in plasma NEFA (17). Cyclopropane causes marked elevation of plasma NEFA which can be inhibited by prior /3-adrenergic blockade
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or reversed by glucose loading. Halothane-nitrous oxide anesthesia causes a rise in plasma NEFA but not as great as with cyclopropane; diethyl ether causes no elevation in plasma NEFA (88). Halothane and methoxyflurane cause a significant rise in plasma NEFA (10). Patients anesthetized by four combinations of anesthet ics, halothane, nitrous oxide, thiopental, and droperidol with fentanyl, for renal arteriography showed no significant changes in plasma NEFA over pre-anesthetic levels, suggesting that in absence of a surgical stress these anesthetics fail to affect lipid metabolism (89). General anesthesia with ether and neuroleptic agents and spinal anesthesia cause no significant alterations in NEFA (l5). The lack of change of plasma NEFA following spinal anesthesia with subsequent sympathetic blockade suggests that elevated plasma NEFA with general anesthetics may involve sympa thetic nervous system stimulation. Nonclinical studies on the effects of inhalational anesthetics on lipid metabolism are sparse. The uptake of free fatty acids by the liver of ether-anesthetized rats is markedly increased compared to unanesthetized rats (90), but this may be related to circulatory changes. Exposure of rat hepatoma cells to halothane results in a marked increase in lipid synthesis (neutral and phospholipid fractions), a slight reduction in DNA and protein synthesis, and no effect on RNA synthesis. Acetate uptake is increased in the presence of halothane (91).
PROTEIN AND NUCLEIC ACIDS METABOLISM Studies of anesthesia and protein metabolism are scarce. Negative nitrogen balance persists longer following ether than after spinal anesthesia (92). Ether and trichloro ethylene, but not nitrous oxide, significantly decrease the rate of incorporation of L-Ieucine into the exocrine cells of the rat pancreas during 15 min of anesthesia. Inhibition also occurs in vitro when slices of pancreas are exposed to anesthetic gases (93). Halothane depresses uptake of leucine and thymidine by rat hepatoma cells with subsequent reduction of DNA and protein synthesis and no effect on RNA synthesis (91). Sulfhydryl groups in brain homogenates suspended in solutions of diethyl ether, chloroform, halothane, methoxyflurane, and trichloroethylene are decreased (94). A correlation exists between anesthetic potency and sulfhydryl reducing effect, suggesting the possibility of conformational changes in brain protein. Hinkley & Telser (95) have recently summarized studies of effects of general anesthetics on the microtubule-microfilament systems which have been implicated in cytoplasmic movement. Allison & Nunn (96) suggest that reversible depolymeri zation of neuronal microtubules by anesthetics might be the basis of general anes thesia, but Sauberman & Gallagher (97) have shown narcosis can occur without microtubular disruption. Actin-like microfilaments are reversibly depolymerized with clinical concentrations of inhalation anesthetic agents (98). These filaments in the eNS are thougnt to involve neurotransmitter release and interaction of anes thetic and microfilament protein has been postulated as a mechanism by which volatile anesthetics affect biomotion phenomena (95).
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Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
SUMMARY Maj or inhalational anesthetics cause inhibition in the electron transport chain in the region of Complex I resulting in decreased oxygen utilization, inhibition of metabo lism of NAD-linked substrates, but not of succinate, inhibition of mitochondrial calcium uptake, and depression of synaptic transmission because of postulated changes in ACh sensitivity or GABA inhibition. Many cellular metabolic effects in CNS and other tissues are secondary to the above. Many metabolic changes noted with anesthetics occur subsequent to activation of the sympathetic nervous system either directly by the anesthetic or by surgical stimulation in the presence of light anesthesia. Many important studies remain to be done. Literature Cited
I. Bunker, J. P. 1963. Neuroendocrine
2.
3.
4. 5.
6.
7. 8.
9.
10.
II. 12.
13.
14.
and other effects on carbohydrate me tabolism during anesthesia. Anesthesi ology 24:515-23 Bunker,1. P. 1962. Metabolic acidosis during anesthesia and surgery. Anes thesiology 23: 107-22 Bunker, J. P., Vandam, L. D. 1965. Effects of anesthesia on metabolism and cellular functions. Pharmacal. Rev. 17:183-263 Fink, B. R. 1969. Cellular biology of anesthesia. Clin. Anesth. 3:109-30 Fink, B. R., Haschke, R. H. 1973. An esthetic effects on cerebral metabolism. Anesthesiology 39:199-215 Greene, N. M. 1963. Inhalation Anes thetics and Carbohydrate Metabolism. Baltimore: Williams & Wilkins. 143 pp. Greene, N. M. 1968. Halothane and metabolism. Clin. Anesth. 1:181-95 Kitahata, L. M., Schmidt, K. F. 1968. Effects of halothane on neuronal tissue. Clin. Anesth. 1:61-84 McIlwain, H. 1966. Biochemistry and the Central Nervous System. Chap 13, 338-58. Boston: Little, Brown Merin, R. G., Samuelson, P. N., Schalch, D. S. 1971. Major inhalation anesthetics and carbohydrate metabo lism. Anesth. Analg. 50:625-32 Pepeu, G. 1974. Progr. Neurobiol. 2:257-88 Quastel,1. H. 1965. Effects of drugs on metabolism of the brain in vitro. Brit. Med. Bull. 21:49-56 Smith, A. L., Wollman, H. 1972. Cere bral blood flow and metabolism. Anes thesiology 36:378-400 Reynoso, A. 1853. Note sur Ie passage du sucre dans les urines a propas d'une note due Docteur Harley sur Ie meme suject. C. R. Soc. Bioi. 5:116-19
15. Oyama, T. 1973. Anesthetic Manage ment oj Endocrine Disease. Chap 9, 118-39, 199-207. New York: Springer Verlag 16. Greene, N. M. 1974. Insulin and anes thesia. Anesthesiology 41:75-79 17. Allison, S. P., Tomlin, P. J., Chamber lain, M. J. 1969. Some effects of anaes thesia and surgery on carbohydrate and fat metabolism. Brit. J. Anaesth. 41:588-93 18. Braun, U., Hensel,l.,Kettler, D., Lohr, B. 197 I. Influence of methoxyflurane, halothane, dipiritramide, barbiturate and ketamine on the total oxygen con sumpation of the dog. Anaesthesist 20:369-75 19. Theye, R. A. 1970. Effect of halothane on canine gastrocnemius-muscle oxy gen consumption. Anesth. Analg. 49:680-86 20. Theye, R. A., Brown, A. L. Jr., Van Dyke, R. A. 1971. The effects of halo thane and succinylcholine on oxygen uptake of the canine gracilis muscle. Anesthesiology 35:304-8 21. Britt, B. A., Kalow, W., Endrenyi, L. 1972. Effects of halothane and methox yflurane on rat skeletal muscle mito Pharmacal. Biochem. chondria. 21: 1159-69 22. Gorden, R. A., Britt, B. A., Kalow, W., Eds. 1973. International Symposium on Malignant Hyperthermia. Springfield: Thomas 23. Brunner, E. A. 1969. The effects of diethyl ether on carbohydrate metabo lism in skeletal muscle. Anesthesiology 30:24-28 24. Jowett, M., Quastel, J. H. 1937. The effect of ether on brain oxidations. Bio chem. J. 31:1101-16
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
ANESTHESIA AND METABOLISM 25. Hoech, G. P., Matteo, R. S., Fink, B. R. 1966. Effect of halothane on oxygen consumption of rat brain, liver and heart and anaerobic glycolysis of rat brain. Anesthesiology 27:770-77 26. Besombe, J., Longmuir, I. S. 1971. Effect of halothane on oxygen consump tion of rat liver slices. Brit. J. Anaesth. 43:1036-42 27. Fink, B. R., Kenny, G. E., Simpson, W. E. 1969. Depression of oxygen up take in cell culture by volatile, barbitu rate and local anesthetics. Anesthesi ology 30:150-55 28. MacBeth, R. A., Haley, F. C. H., Bekesi, J. G. 1961. Cellular metabolism of surviving tissue slices following vari ous types of anesthesia. Surg. Forum 12:11-12 29. Bombeck, C. T., Aoki, T., Smuckler, E. A., Nyhus, L. M. 1969. Effects of halothane, ether and chloroform on the isolated, perfused, bovine liver. Am. J. Surg. 117:91-107 30. Strunin, L. et al 1970. A comparison of the effects of halothane and methoxyflu rane on the isolated perfused canine liver. Acta Anaesthesiol Scand. Suppl 37:203-4 31. Biebuyck, J. F., Lund, P., Krebs, H. A. 1972. The effects of halothane (2bromo-2-chloro-l ,I, I-trifluorethane) on glycolysis and biosynthetic processes of the isolated perfused rat liver. Bio chem. J. 128:711-20 32. Biebuyck, 1. F., Lund, P., Krebs, H. A. 1972. The protective effect of oleate on metabolic changes. Biochem. J. 128:721-23 33. Biebuyck, J. F. 1973. Anesthesia and hepatic metabolism. Anesthesiology 39:188-98 34. Biebuyck,1. F., Lund, P. 1974. Effects of halothane and other anesthetic agents on the concentrations of rat liver metabolites in vivo. Mol. Pharmacol. 10:474-83 35. Keilin, D., Hartree, E. F. 1940. Succinic dehydrogenase-cytochrome system of cells: intracellular respiratory system catalysing aerobic oxidation of succinic acid. Proc. Roy. Soc. London B 129:277-306 36. Eiler, J. J., McEwan, W. K. 1949. The effect of pentobarbital on aerobic phos phorylation in brain hemogenates. Arch. Biochem. Biophys. 20:163-65 37. Ernster, L., Jailing, 0., Low, H., Lind berg, O. 1955. Alternative pathways of mitochondrial DPNH oxidation, stud-
38.
39.
40.
41.
42.
43.
44.
45.
46.
47. 48.
49.
50.
51.
52.
399
ied with amytal. Exp. Cell. Res. Suppl. 3:124-32 Cohen, P. J., Marshall, B. E., Harris, J. E., Lecky, J. H., Rosner, B. S. 1968. Fed. Proc. 27:2744 (Abstr.) Cohen, P. J., Marshall, B. E. 1968. Tox icity of Anesthetics, ed. B. R. Fink, Chap. 3, 24-36. Baltimore: Williams & Wilkins Cohen, P. J., Marshall, B. E., Lecky, B. A. 1969. Effects of halothane on mitochondrial oxygen uptake: site of ac tion. Anesthesiology 30:337 Cohen, P. J., McIntyre, R. A. 1972. Cel lular Biology and Toxicity of Anesthet ics, ed. B. R. Fink, Chap 10, 109-16. Baltimore: Williams & Wilkins. 328 pp. Hall, G. M., Kirtland, S. J., Baum, H. 1973. The inhibition of mitochondrial respiration by inhalational anaesthetic agents. Brit. J. Anaesth. 45: 1005-9 Harris, R. A., Munroe, J., Farmer, B., Kim, K. C., Jenkins, P. 1971. Action of halothane upon mitochondrial respira tion. Arch. Biochem. Biophys. 142: 435-44 Nahrwold, M. L., Cohen, P. J. 1973. The effects of forane and fluroxene on mitochondrial respiration. Anesthesi ology 39:437-44 Miller, R. N., Hunter, F. E. 1971. Is halothane a true uncoupler of oxidative phosphorylation? Anesthesiology 35: 256-61 Miller, R. N., Hunter, F. E. 1970. The effect of halothane on electron trans port, oxidative phosphorylation and swelling in rat liver mitochondria. Mol. Pharmacol. 6:67-77 See Ref. 41. 93-108 Miller, R. N., Schumer, W., Erve, P. R. 1972. The effects of halogenated anes thetics on mitochondrial function. Anesthesiology 36:625-27 Schumer, W., Erve, P. R., Obernolte, R. P., Bombeck, C. T., Sadove, M. S. 197 J. The effect of inhalation of haloge nated anesthetics on rat liver mitochon drial function. Anesthesiology 35: 253-55 Schumer, W., Erve, P. R., Obernolte, R. P., Bombeck, C. T., Sadove, M. S. 1972. Halogenated anesthetics' effect on rat liver mitochondria. Z. Exp. Chir. 5:\3-16 Michenfelder, J. D., Theye, R. A. 1972. Effects of cyclopropane on canine cere bral blood flow and metabolism. Anes thesiology 37:32-39 Michenfelder,1. D., Theye, R. A. 1973. Effects of methoxyflurane on canine
400
53.
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
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55.
56.
57.
58.
59.
60.
61.
62.
63.
64. 65.
66.
BRUNNER, CHENG & BERMAN cerebral metabolism and blood flow. Anesthesiology 38: 123-27 Smith, A. L. 1973. The mechanism of cerebral vasodilation by halothane. Anesthesiology 39:581-87 Matteo, R. S., Hoech, G. P., Hoskin, F. C. G. 1969. Effects of cyclopropane and diethyl ether on tissue oxygen con sumption and anaerobic glycolysis of brain in vitro. Anesthesiology 30:15�3 Hoesin, E. A., Stachiewicz, E., Bourne, W., Demstedt, O. F. 1955. The influ ence of nitrous oxide on the metabolic activity of brain tissue. Anesthesiology 16:708-15 Biebuyck, J. F., Hawkins, R. A. 1972. The effect of anaesthetic agents on brain tissue metabolite patterns. Brit. J. Anaesth. 44:226-27 Brunner, E. A., Passonneau, J. V., Mol stad, C. 1971. The effect of volatile an aesthetics on levels of metabolites and on metabolic rate in brain. J. Neuro chem. 18:2301-16 Heim, F., Esteler, c.-J., Ammon, H. P.
T., Picker, D. 1966. Effect of trichloro
ethylene on brain levels of high energy phosphate, coenzyme A and glycolytic metabolites in white mice. Arch. Int. Pharmacodyn. Ther. 162:311-18 Nilsson, L., Siesjo, B. K. 1970. The effect of anesthetics upon labile phos phates and upon extra- and intra-cellu lar lactate, pyruvate and bicarbonate concentrations in the rat brain. Acta Physiol. Scand. 80:235.,.48 Goldberg, N. D., Passonneau, J. V., Lowry, O. H. 1966. The effects of changes in brain metabolism on the lev els of citric acid cycle intermediates. J. Bioi. Chem. 17:3997.,.4003 Doring, H. J., Olbrisch, R. R., Schrader, J., Lang, H. 1970. Electrocor ticograms, steady potential of the brain and energy-rich phosphate fractions of the cerebral cortex during anesthetic overdosage, ischemia and cyanide poi soning. Pjieuger S Arch. 319:12-35 Gatz, E. E., Schoettger, J. D., Morgan, J. R., Bird, J. S., Jones, J. R. 1971. Fed. Proc. 30:442 (Abstr. 1378) Gatz, E. E., Jones, J. R. 1969. Fed. Proc. 28:356 (Abstr. 353) Brody, T. M., Bain, J. A. 1954. Barbitu rates and oxidative phosphorylation. J. Pharmacol. Exp. Ther. 110:148-56 Smith, H. 1973. Effect of halothane upon rabbit brain mitochondria. Bio chem. Pharmacol. 22:773-81 Rosenberg, H., Haugaard, N. 1973. The effects of halothane on metabolism and
67.
68.
69.
70.
71.
72.
calcium uptake in mitochondria of the rat liver and brain. Anesthesiology 39:#-53 Miller, R. N., Miller, E., Caine, J., Sta bler, M. 1974. Synaptosomes, a possible system for the study of synaptic trans mission. Anesth. Analg. 53:132.,.41 Johnson, W. J., Quastel, J. H. 1953. A comparison of the effects of narcotics and 2,4-dinitrophenol on sulfanilamide acetylation. J. Biol Chem. 205:163-71 Cheng, S.-c., Brunner, E. A. 1975. Molecular Mechanisms of Anesthesia, ed. B. R. Fink. New York: Raven. In press Cremer, J. E., Lucas, H. M. 1971. Sodium pentobarbitone and metabolic compartments in rat brain. Brain Res. 35:619-21 Hakim, A. M., Moss, G. 1974. The effect of ether anesthesia on cerebral glucose metabolism-the pentose phos phate pathway. Anesthesiology 40: 261-67 Hassler, C., Hassler, R., Okada, Y., Bak,
73.
74.
75.
76.
77.
78.
79.
I.
J.
1971.
Pre-ictal
and
ictal
changes of serotonin, GABA and gluta mate contents in different regions of rabbit brain during methoxypyridoxine induced seizures. Acta Neurol. Lat inoamer. 17:595-611 Reynolds, A. P., Gallagher, B. B. 1973. The effect of hexafluorodiethyl ether (flurothyl) on the metabolism of rat brain amino acids labelled by (U-I.C) glucose. Life Sci. 13:87-95 Reynolds, A. P., Watkins, J. C. 1972. The effect of strychnine and of electrical stimulation on the labelling of 'Y aminobutyric acid and other free amino acids from (U-I'C) glucose in the spinal cord of the nembutalized rat. Brain Res. 36:343-51 Balazs, R., Cremer, J. E., 1973. Meta bolic Compartmentation in the Brain. London: Macmillan. 383 pp. Grewaal, D. S., Quastel, J. H. 1973. Control of synthesis and release of ra dioactive acetylcholine in brain slices from the rat. Biochem. J. 132:1-14 Sharkawi, M. 1970. Effects of morphine and pentobarbitone on acetylcholine synthesis by rat cerebral cortex. Brit. J. Pharmacol. 40:86-91 Sundwall, A. 1973. Effect of pentobar bital on the turnover of acetylcholine in brain nerve terminals in vivo. Brain Res. 62:531-36 Domino, E. F., Wilson, A. E. 1972. Psy chotropic drug influences on brain ace-
ANESTHESIA AND METABOLISM
80.
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
81.
82.
83.
84.
85.
86.
87.
tylcholine utilization. Psychopharmacologia 25:291-98 Jones, B. E., Guyenet, P., Cher�my, A., Gauchy, C., G1owinski, J. 1973 The in vivo release of acetylcholine flOm cat caudate nucleus after pharmacological and surgical manipulations of dopamin ergic nigrostriatal neurons. Brain Res. 64:355-69 Tappaz, P. M., Tacheco, H. 1973. Effects of convulsant and anticonvul sant drugs on the spontaneous and in duced release of GABA(14C) from cor tex slices of rat brain. J. Pharmacol. (Paris) 4:433-52 Cutler, R. W. P., Dudzinski, D. S. 1974. Effect of pentobarbital on uptake and release of (lH)GABA and (14C) gluta mate by brain slices. Brain Res. 67:546-48 Blagoeva, P., Longo, V. G., Masi, I., Scotti de Carolis, A. 1972. Alterations in behavior, EEG, and brain cortical GABA content following prolonged ad ministration and subsequent with drawal of barbital in the rat. Behav. Bioi. 7:755-60 Tsuji, H., Balagot, R. C., Sadove, M. S. 1963. Effect of anesthetics on brain gamma-aminobutyric and glutamic acid levels. J. Am. Med. Assoc. 183:659-61 Harris, M., Hopkin, J. M., Neal, M. J. 1973. Effect of centrally acting drugs on the uptake of y-aminobutyric acid (GABA) by slices of rat cerebral cortex. Brit. J. Pharmacol. 47:229-39 Chance, B., Cohen, P., 10bsis, F., Scho ener, B. 1962. Intracellular oxidation reduction states in vivo. Science 137:499-508 Merin, R. G. 1975. See Ref. 69
401
88. Cooperman, L. H. 1970. Plasma free fatty acid levels during general anes thesia and operation in man. Brit. J. Anaesth. 42:131-35 89. Tarhan, S., Fulton, R. E., Moffitt, E. A. 1971. Body metabolism during general anesthesia without superimposed surgi cal stress. Anesth. Analg. 50:915-23 90. Schotz, M. C., Olivecrona, T. 1966. The effect of anesthesia on the fate of in jected free fatty acid. Biochim. Biophys. Acta 125:174-75 91. Ishii, D. N., Corbascio, A. N. 1971. Some metabolic effects of halothane on mammalian tissue culture cells in vitro. Anesthesiology 35:427-38 92. Manku, R. S. 1970. Effect of anesthesia on protein metabolism in patients un dergoing hemioplasty. Anesth. Analg. 49:446-49 93. Kramer, M. F., Poort, C. 1972. Influ ence of anaesthetic drugs on amino acid incorporation in the rat pancreas. Bio chem. Pharmacol. 21:441-47 94. Ho, I. K., Keats, A. S. 1969. Effect of anesthetics on sulfhydryl content of rat brain. Pharmacology 2:257-64 95. Hinkley, R. E., Telser, A. G. 1974. See Ref. 69 96. Allison, A. C., Nunn, J. F. 1968. Effects of general anesthetics on microtubules: a possible mechanism of anesthesia. Lancet 3:1326--29 97. Sauberman, A. J., Gallagher, M. L. 1973. Mechanisms of general anes thesia: failure of pentobarbital and halo thane to depolymerize microtubules in mouse optic nerve. Anesthesiology 38:25-31 98. Wiklund, R. A., Allison, A. C. 1972. Effects of anaesthetics on the motility of Dictyostelium discoideum. Nature (New BioL) 239:221-22 .
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Copyright 1975. All rights reserved
EFFECTS OF ANESTHESIA ON
+7160
INTERMEDIARY METABOLISM Edward A. Brunner, MD., PhD., S. C Cheng, PhD., and M L. Berman, MD., PhD. Department of Anesthesia, Northwestern University Medical School, Chicago, Illinois
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INTRODUCTION Some order is beginning to emerge from the confusion concerning metabolic effects of anesthetics which Bunker noted only a dozen years ago ( 1). Early clinical observa tions, many lacking in scientific merit, have given way to well designed and executed studies focusing on specific problems. Most reports have been directed to carbohy drate or energy metabolism in the intact organism, liver, or central nervous system. Prior reviews of interest have appeared (I-B).
CARBOHYDRATE METABOLISM Carbohydrate homeostasis reflects the balance of a complex set of interactions including intestinal absorption, peripheral substrate utilization, the effects of endo crine factors (insulin, glucagon, steroids, growth hormone), gluconeogenesis, glycogenolysis in liver and muscle, lipolysis, and renal clearance of glucose. Anes thetics affect all of these. Systemic Manifestations
Reynoso first observed glycosuria after ether anesthesia in 1853 ( 14). Most anesthet ics, with the possible exceptions of enflurane and methoxyflurane, are associated with hyperglycemia but not with a rise in plasma insulin level ( 15). The ratio of plasma insulin/plasma glucose falls ( 16), indicating that certain anesthetics may partially inhibit insulin release from the pancreas. This is best substantiated for halothane. The role of sympathetic inhibition in this anesthetic depression of insulin secretion has yet to be fully explored, although one observation ( 17) reports that phentolamine did not prevent the failure of insulin response to infused glucose during halothane anesthesia. 391
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Skeletal Muscle Theye and his co-workers attempted to define the organ site of the decrease in whole body oxygen consumption which accompanies general anesthesia ( 18). They showed that oxygen consumption of in situ canine gracilis and gastrocnemius muscles, two markedly dissimilar muscles, decrease equally with increase in halothane concentra tion ( 19, 20). This justifies proportional extrapolation to all skeletal muscle, which accounts for 30 to 40% of total body oxygen consumption. Both halothane and methoxyflurane (21) at ciinical concentrations inhibit state 3 (ADP present) respira tion of rat skeletal muscle mitochondria with glutamate as substrate, but not with succinate. State 4 respiration (ADP absent) with both glutamate and succinate is virtually unalfected. These anesthetics block electron transport in skeletal muscle as they do in brain and liver (see below), and thus reduce oxygen consumption and heat production generated by normal muscle activity. The syndrome of malignant hyperpyrexia has been the subject of a recent symposium (22). In isolated rat hemidiaphragm (23) ether depresses glucose uptake but does not block insulin stimulation of glucose uptake. It increases lactate formation from glycogen; in the presence of insulin lactate formation is doubled. Normally; hemidia phragm converts to glycogen 70% of the increased glucose uptake due to insulin. In the presence of ether only 50% is converted to glycogen, the remainder appearing
as lactate.
Liver Jowett & Quastel (24) reported that rat liver respiration was not alfected by diethyl ether. More recent studies (25, 26) demonstrate that halothane produces a dose related reversible depression of oxygen consumption and an increase in glycolysis by rat liver slices. Fink (27), using cultured mouse heteroploid cells, showed that methoxyflurane, halothane, chloroform, and diethyl ether depress oxygen uptake and increase glycolytic rate in order of potency related to the hypnotic activity of the drug. One study (28) of liver slices from anesthetized dogs failed to show changes, probably because of loss of volatile anesthetics from the tissue prior to measurement. Isolated perfused bovine (29), canine (30), and rat liver (31) have been employed to study anesthetic elfects on metabolism. With dog liver, 2% chloroform and 1 % methoxyflurane caused glucose release, increased lactate/pyruvate ratio, and loss of potassium and cellular enzymes from the liver. Halothane produced no measurable alterations. In bovine and rat liver chloroform, diethyl ether, halothane, and me thoxyflurane (where studied) cause depression of oxygen consumption, lactate utili zation, gluconeogenesis, and glycogen synthesis but stimulate release of glucose or lactate into the perfusate. Urea synthesis is depressed and cellular integrity as measured by loss of cellular enzymes and potassium is altered reversibly by chloro form and high concentrations of ether. In fed rats there is a marked decrease in tissue content of both 2-oxoglutarate and citrate and a decrease in calculated NAD/NADH ratio for both cytoplasmic and mitochondrial couples. These findings are consistent with stimulation of glycogenolysis and glycolysis and inhibition of gluconeogenesis and oxidative metabolism. The lack of inhibition of fatty acid
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oxidation (32) and the decrease in NAD/NADH ratios lead to the speculation of anesthetic inhibition in the region of NADH dehydrogenase as a major site of anesthetic action (33). In vivo studies of liver utilizing freeze-clamping techniques (34) show that halo thane, methoxyflurane, trichloroethylene, and diethyl ether all cause elevated blood and tissue glucose levels and depletion of liver glycogen. In contrast to in vitro studies, halothane caused no lactate accumulation in the liver in vivo. Lactate/pyru vate ratios remain normal even when lactate levels rise, as with trichloroethylene and diethyl ether anesthesia. With halothane, decreases in liver ATP and shift of cytoplasmic and mitochondrial redox couples to a more reduced state do not occur in the intact, as they do in the perfused, liver. Decreases in the liver 2-oxoglutarate levels occur but are less severe (20% of normal in vivo, 50% in vitro) and are accompanied by parallel alterations of glutamate, indicating the presence of intact control mechanisms not functional in the isolated perfused preparation. Attempts to precisely characterize the basic cellular actions of narcotics have led to demonstrations, first, that urethane and certain alcohols produce a metabolic block of electron transfer (35) and later, that amobarbital and other barbiturates inhibit mitochondrial oxidation of pyruvate and fumarate, but not of succinate (36). This amobarbital inhibition was later extended to all NAD-linked mitochondrial oxidations (37). Cohen and co-workers have shown that halothane in concentrations up to 2% (38-40) reversibly blocks NAD-linked substrate oxidation but does not block succinate oxidation. Only amobarbital-sensitive but not amobarbital-insensi tive oxidations are blocked. The site of halothane inhibition occurs in the region of Complex I between NADH dehydrogenase and coenzyme Q (Figure 1), at or near the site(s) of the inhibiting action of rotenone and amobarbital (4 1 -43). NAD-Linked Substrate
Succinate
�
�
In
Is
�
�
Non-heme Iron----::)(�--I CoQ Figure I.
-
Cytochrome Chain
-
02
S ite of anesthetic inhibition of electron transport.
Methoxyflurane, diethyl ether, enflurane, forane, fluroxene, trichloroethylene, and chloroform in anesthetic concentrations subsequently have been shown to demonstrate a dose-dependent reversible inhibition of electron transport in a way similar to halothane. The concentrations of six anesthetics necessary for 50% inhibi tion of state 3 respiration bears an inverse log-log relationship to their lipid solubility (44). Potency as electron transport inhibitor in vitro is directly related to anesthetic potency in vivo. Miller & Hunter (45) suggest that errors in experimental design in some studies have caused inadvertent mitochondrial damage due to exposure to excessive concen trations of halothane and have led to the erroneous conclusion that halothane is a
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true uncoupling agent. By contrast, studies of mitochondrial calcium transport (45) in which halothane exposure is carefully controlled show that concentrations as high as 4% do not alter the final steady state of calcium accumulation as would a true uncoupler. Moreover, the response of rapid calcium release on addition of a true uncoupler remains intact, indicating that halothane acts differently than a true uncoupler. There is evidence that methoxyflurane and diethyl ether (41) at anesthetic concen tration, and others at higher concentrations (46), have additional actions on mito chondrial function, including inhibition of succinate oxidation, some degree of uncoupling, loss of respiratory control, and alteration of the mitochondrial mem brane (46-50). The possibility that anesthetics alter membrane permeability and thereby affect metabolic function by altering the delivery of substrate to the site of utilization has been suggested (4 1), based on data observed in rat atria and human red cells as well as in mitochondria. Further implications of the above cited findings have yet to be fully evaluated.
Central Nervous System Metabolism in the nervous system subserves three main functions: 1: to maintain structural integrity, 2. to maintain ionic and electrical gradients across excitable membranes, and 3. to synthesize neurotransmitters. The major metabolic effects of anesthetics relate to the latter two. The following discussion will address effects of volatile anesthetics on energy metabolism, on incorporation and turnover of tracer compounds, and on neurotransmitters. The effect of volatile anesthetics on the respiration of intact brain in vivo is uniformly inhibitory (5 1-53). The exact extent of this inhibi tion varies for different agents and species. Several factors (Poz, Pcoz, blood pres sure, vascular resistance, temperature, the anesthetic agent employed, and cerebral blood flow) are important in determining the degree of respiratory inhibition ( 13, 53). With brain slices, anesthetic agents reduce the additional increment of oxygen utilization due to stimulation by electrical current or high potassium concentration before the resting respiration is altered. The concentration of anesthetic agent required in vitro is usually higher than that in vivo (9). With few exceptions, anesthetic agents depress oxygen consumption by cerebral cortex slices, by chopped brain suspensions, and by brain homogenates (9, 12, 54, 55). Volatile anesthetic agents cause varied changes in lactate content and glycolysis in the in vivo brain, in slices, and in homogenates (5, 9, 54--59). The recent data demonstrating decreased lactate in brain material recovered with a "brain blower" deserve special mention. Total tissue high energy phosphate content is not altered by volatile anesthetic agents (9, 56, 58-6 1). Glucose and glycogen can be added to the high energy reserve to represent total energy stores. These increase as metabolic rate is depressed by anesthetics (56-58). ENERGY METABOLISM
MITOCHONDRIAL AND SYNAPTOSOMAL METABOLISM Crude brain mito chondria can be separated into several subfractions, including synaptosomes and heavy mitochondria. The respiration and oxidative phosphorylation of crude mito-
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chondria supported by pyruvate, glutamate, or 2-oxoglutarate are inhibited by halothane and methoxyflurane but not by nitrous oxide, diethyl ether, chloroform, or cyclopropane (62). Presumably, halothane uncouples oxidative phosphorylation of this crude preparation (63). This idea of "uncoupling," put forth in the early fifties (64), is supported by more recent work using purified mitochondria from rabbit brain and high concentrations of halothane (65), but disputed by work using rat brain mitochondria (66). This latter report demonstrates that halothane inhibits ADP-stimulated respiration of mitochondria metabolizing glutamate. This inhibit ing effect is virtually absent with succinate. Calcium uptake is also found to be inhibited by halothane. These results have been confirmed in a concurrent study using both mitochondrial and synaptosomal preparations (67). The succinate rever sal of anesthetic-inhibited respiration was first observed many years ago (55, 68) without adequate explanation. It appears likely that further studies will confirm an anesthetic sensitive site in electron transport similar to that already identified in liver mitochondria. The validity of results based on the cerebral metabolism of labeled substrates is often in question due to the large cerebral blood flow which introduces a "contaminating" effect from metabolism of other body tissues. This compounds difficulties caused by the postmortem changes which are well known in neurochemistry. Anesthetic agents alter amino acid labeling in the brain and spinal cord. In general (56-58, 60, 69-74), the incorporation of glucose carbon into aspar tate, glutamate, glutamine, and y-aminobutyrate is reduced but similar incorpora tion into alanine is variable, Glutamate content is unchanged or decreased. Incorporation of carbons from acetate, butyrate, and citrate is not affected. These differences observed in the incorporation of labeled carbon from different substrates can be interpreted by the concept of metabolic compartmentation (75). Two groups of substrates are known to be metabolized by different compartments and their correlated anatomic entities have been respectively assigned to nerve endings and glia. The anesthetic agents appear to inhibit primarily the glucose utilizing compart ment, i.e. the nerve endings (69). TRACER EXPERIMENTS
NEUROTRANSMITTERS This section includes data on the effect of amobarbital, chloralose, allobarbital, hydroxydione, methylpentyol, pentobarbital, thiopental, phenobarbital, and the volatile anesthetics on synthesis, degradation, release, up take, and other mechanisms of removal from site(s) of action of neurotransmitters. Most inhibit the synthesis of acetylcholine (ACh) ( 1 2, 68, 69, 76-78) and cause increased ACh content in vivo (8, 79, 80), which is attributed to nonutilization. In contrast, the ACh content of slices exposed to halothane is lower than that of controls and its synthesis from acetate is not altered (69). The release of ACh is reduced by anesthetic agents (1 1 , 76, 8 1 ) and its turnover rate is decreased (69, 78). Anesthetic agents cause reduced synthesis of y-aminobutyrate (GABA) in rat cortex slices (69); release is not affected (81). In stimulated slices barbital causes increased GABA release (82). GABA content in rat brain varied (83, 84) and GABA uptake by rat cortex slices also varied (69, 82, 85).
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The primary manner of the removal of GABA from synaptic areas is by re-uptake by cells near the synapses followed by enzymatic degradation via the GABA shunt, a unique metabolic pathway in the brain. A glial function for such removal has been advanced. This whole matter concerning GABA requires further clarification. HYPOTHESIS OF ANESTHETIC ACTION The increase in energy stores, the re duced metabolic rate (oxygen consumption), and the reduced incorporation of glucose carbon into intermediate metabolites suggest a decreased utilization of energy in brain during anesthesia. Earlier theories based on the inhibition of energy production as the primary cause of anesthesia failed when the energy stores were found not to decrease and the reduction of cerebral NAD could not be demonstrated (59, 86). In vivo inhibition of synaptic transmission was found to precede axonal block by anesthetic agents, suggesting that neurotransmitters may play a crucial role in anesthesia mechanisms. Two lines of thought have been proposed. One suggests that the increased cytoplasmic calcium concentration, induced by impaired mito chondrial uptake of calcium under influence of anesthetic agents, may cause reduced sensitivity to excitation by ACh (66, 67). This idea requires no participation of an inhibitory synapse which some physiological experiments have suggested. The other theory postulates that degradation of GABA is retarded by anesthetic block of Complex I. This causes a rise in synaptic GABA content followed by synaptic inhibition. Regardless of the cause of the decreased synaptic activity, the outward manifestation would be anesthesia. A decrease in synaptic work requires less utiliza tion of energy for ionic transport. Extra energy is shifted to the synthesis of energy rich compounds such as glycogen, lipids, and glutamine. The energy-producing reactions (respiration and glycolysis) are somewhat reduced. This oversimplified hypothesis is attractive. It agrees with most neurochemical findings. The details are more difficult to formulate. For example, glial functions, which are just being investigated, may contribute heavily in the overall mechanism of anesthesia.
Miscellaneous The effects of inhalation anesthetics on myocardial metabolism have been included in a recent review of Merin (87) and interested readers are referred thereto. Isolated studies of anesthetic effects on lung and kidney metabolism and of adrenal enzyme activity have been reported. A few isolated studies of anesthetic effect on specific enzymes have also been reported, but systematic analysis of results is not yet possible.
FAT METABOLISM Studies of anesthetic effects on lipid metabolism in man have focused on the changes in the plasma levels of nonesterified fatty acids (NEFA). In most studies adequate control of pertinent parameters is lacking or not recorded. Pre-anesthetic emotional stress and surgical stress are more significant than nitrous oxide-halothane anes thesia in causing a marked rise in plasma NEFA (17). Cyclopropane causes marked elevation of plasma NEFA which can be inhibited by prior /3-adrenergic blockade
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or reversed by glucose loading. Halothane-nitrous oxide anesthesia causes a rise in plasma NEFA but not as great as with cyclopropane; diethyl ether causes no elevation in plasma NEFA (88). Halothane and methoxyflurane cause a significant rise in plasma NEFA (10). Patients anesthetized by four combinations of anesthet ics, halothane, nitrous oxide, thiopental, and droperidol with fentanyl, for renal arteriography showed no significant changes in plasma NEFA over pre-anesthetic levels, suggesting that in absence of a surgical stress these anesthetics fail to affect lipid metabolism (89). General anesthesia with ether and neuroleptic agents and spinal anesthesia cause no significant alterations in NEFA (l5). The lack of change of plasma NEFA following spinal anesthesia with subsequent sympathetic blockade suggests that elevated plasma NEFA with general anesthetics may involve sympa thetic nervous system stimulation. Nonclinical studies on the effects of inhalational anesthetics on lipid metabolism are sparse. The uptake of free fatty acids by the liver of ether-anesthetized rats is markedly increased compared to unanesthetized rats (90), but this may be related to circulatory changes. Exposure of rat hepatoma cells to halothane results in a marked increase in lipid synthesis (neutral and phospholipid fractions), a slight reduction in DNA and protein synthesis, and no effect on RNA synthesis. Acetate uptake is increased in the presence of halothane (91).
PROTEIN AND NUCLEIC ACIDS METABOLISM Studies of anesthesia and protein metabolism are scarce. Negative nitrogen balance persists longer following ether than after spinal anesthesia (92). Ether and trichloro ethylene, but not nitrous oxide, significantly decrease the rate of incorporation of L-Ieucine into the exocrine cells of the rat pancreas during 15 min of anesthesia. Inhibition also occurs in vitro when slices of pancreas are exposed to anesthetic gases (93). Halothane depresses uptake of leucine and thymidine by rat hepatoma cells with subsequent reduction of DNA and protein synthesis and no effect on RNA synthesis (91). Sulfhydryl groups in brain homogenates suspended in solutions of diethyl ether, chloroform, halothane, methoxyflurane, and trichloroethylene are decreased (94). A correlation exists between anesthetic potency and sulfhydryl reducing effect, suggesting the possibility of conformational changes in brain protein. Hinkley & Telser (95) have recently summarized studies of effects of general anesthetics on the microtubule-microfilament systems which have been implicated in cytoplasmic movement. Allison & Nunn (96) suggest that reversible depolymeri zation of neuronal microtubules by anesthetics might be the basis of general anes thesia, but Sauberman & Gallagher (97) have shown narcosis can occur without microtubular disruption. Actin-like microfilaments are reversibly depolymerized with clinical concentrations of inhalation anesthetic agents (98). These filaments in the eNS are thougnt to involve neurotransmitter release and interaction of anes thetic and microfilament protein has been postulated as a mechanism by which volatile anesthetics affect biomotion phenomena (95).
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SUMMARY Maj or inhalational anesthetics cause inhibition in the electron transport chain in the region of Complex I resulting in decreased oxygen utilization, inhibition of metabo lism of NAD-linked substrates, but not of succinate, inhibition of mitochondrial calcium uptake, and depression of synaptic transmission because of postulated changes in ACh sensitivity or GABA inhibition. Many cellular metabolic effects in CNS and other tissues are secondary to the above. Many metabolic changes noted with anesthetics occur subsequent to activation of the sympathetic nervous system either directly by the anesthetic or by surgical stimulation in the presence of light anesthesia. Many important studies remain to be done. Literature Cited
I. Bunker, J. P. 1963. Neuroendocrine
2.
3.
4. 5.
6.
7. 8.
9.
10.
II. 12.
13.
14.
and other effects on carbohydrate me tabolism during anesthesia. Anesthesi ology 24:515-23 Bunker,1. P. 1962. Metabolic acidosis during anesthesia and surgery. Anes thesiology 23: 107-22 Bunker, J. P., Vandam, L. D. 1965. Effects of anesthesia on metabolism and cellular functions. Pharmacal. Rev. 17:183-263 Fink, B. R. 1969. Cellular biology of anesthesia. Clin. Anesth. 3:109-30 Fink, B. R., Haschke, R. H. 1973. An esthetic effects on cerebral metabolism. Anesthesiology 39:199-215 Greene, N. M. 1963. Inhalation Anes thetics and Carbohydrate Metabolism. Baltimore: Williams & Wilkins. 143 pp. Greene, N. M. 1968. Halothane and metabolism. Clin. Anesth. 1:181-95 Kitahata, L. M., Schmidt, K. F. 1968. Effects of halothane on neuronal tissue. Clin. Anesth. 1:61-84 McIlwain, H. 1966. Biochemistry and the Central Nervous System. Chap 13, 338-58. Boston: Little, Brown Merin, R. G., Samuelson, P. N., Schalch, D. S. 1971. Major inhalation anesthetics and carbohydrate metabo lism. Anesth. Analg. 50:625-32 Pepeu, G. 1974. Progr. Neurobiol. 2:257-88 Quastel,1. H. 1965. Effects of drugs on metabolism of the brain in vitro. Brit. Med. Bull. 21:49-56 Smith, A. L., Wollman, H. 1972. Cere bral blood flow and metabolism. Anes thesiology 36:378-400 Reynoso, A. 1853. Note sur Ie passage du sucre dans les urines a propas d'une note due Docteur Harley sur Ie meme suject. C. R. Soc. Bioi. 5:116-19
15. Oyama, T. 1973. Anesthetic Manage ment oj Endocrine Disease. Chap 9, 118-39, 199-207. New York: Springer Verlag 16. Greene, N. M. 1974. Insulin and anes thesia. Anesthesiology 41:75-79 17. Allison, S. P., Tomlin, P. J., Chamber lain, M. J. 1969. Some effects of anaes thesia and surgery on carbohydrate and fat metabolism. Brit. J. Anaesth. 41:588-93 18. Braun, U., Hensel,l.,Kettler, D., Lohr, B. 197 I. Influence of methoxyflurane, halothane, dipiritramide, barbiturate and ketamine on the total oxygen con sumpation of the dog. Anaesthesist 20:369-75 19. Theye, R. A. 1970. Effect of halothane on canine gastrocnemius-muscle oxy gen consumption. Anesth. Analg. 49:680-86 20. Theye, R. A., Brown, A. L. Jr., Van Dyke, R. A. 1971. The effects of halo thane and succinylcholine on oxygen uptake of the canine gracilis muscle. Anesthesiology 35:304-8 21. Britt, B. A., Kalow, W., Endrenyi, L. 1972. Effects of halothane and methox yflurane on rat skeletal muscle mito Pharmacal. Biochem. chondria. 21: 1159-69 22. Gorden, R. A., Britt, B. A., Kalow, W., Eds. 1973. International Symposium on Malignant Hyperthermia. Springfield: Thomas 23. Brunner, E. A. 1969. The effects of diethyl ether on carbohydrate metabo lism in skeletal muscle. Anesthesiology 30:24-28 24. Jowett, M., Quastel, J. H. 1937. The effect of ether on brain oxidations. Bio chem. J. 31:1101-16
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
ANESTHESIA AND METABOLISM 25. Hoech, G. P., Matteo, R. S., Fink, B. R. 1966. Effect of halothane on oxygen consumption of rat brain, liver and heart and anaerobic glycolysis of rat brain. Anesthesiology 27:770-77 26. Besombe, J., Longmuir, I. S. 1971. Effect of halothane on oxygen consump tion of rat liver slices. Brit. J. Anaesth. 43:1036-42 27. Fink, B. R., Kenny, G. E., Simpson, W. E. 1969. Depression of oxygen up take in cell culture by volatile, barbitu rate and local anesthetics. Anesthesi ology 30:150-55 28. MacBeth, R. A., Haley, F. C. H., Bekesi, J. G. 1961. Cellular metabolism of surviving tissue slices following vari ous types of anesthesia. Surg. Forum 12:11-12 29. Bombeck, C. T., Aoki, T., Smuckler, E. A., Nyhus, L. M. 1969. Effects of halothane, ether and chloroform on the isolated, perfused, bovine liver. Am. J. Surg. 117:91-107 30. Strunin, L. et al 1970. A comparison of the effects of halothane and methoxyflu rane on the isolated perfused canine liver. Acta Anaesthesiol Scand. Suppl 37:203-4 31. Biebuyck, J. F., Lund, P., Krebs, H. A. 1972. The effects of halothane (2bromo-2-chloro-l ,I, I-trifluorethane) on glycolysis and biosynthetic processes of the isolated perfused rat liver. Bio chem. J. 128:711-20 32. Biebuyck, 1. F., Lund, P., Krebs, H. A. 1972. The protective effect of oleate on metabolic changes. Biochem. J. 128:721-23 33. Biebuyck, J. F. 1973. Anesthesia and hepatic metabolism. Anesthesiology 39:188-98 34. Biebuyck,1. F., Lund, P. 1974. Effects of halothane and other anesthetic agents on the concentrations of rat liver metabolites in vivo. Mol. Pharmacol. 10:474-83 35. Keilin, D., Hartree, E. F. 1940. Succinic dehydrogenase-cytochrome system of cells: intracellular respiratory system catalysing aerobic oxidation of succinic acid. Proc. Roy. Soc. London B 129:277-306 36. Eiler, J. J., McEwan, W. K. 1949. The effect of pentobarbital on aerobic phos phorylation in brain hemogenates. Arch. Biochem. Biophys. 20:163-65 37. Ernster, L., Jailing, 0., Low, H., Lind berg, O. 1955. Alternative pathways of mitochondrial DPNH oxidation, stud-
38.
39.
40.
41.
42.
43.
44.
45.
46.
47. 48.
49.
50.
51.
52.
399
ied with amytal. Exp. Cell. Res. Suppl. 3:124-32 Cohen, P. J., Marshall, B. E., Harris, J. E., Lecky, J. H., Rosner, B. S. 1968. Fed. Proc. 27:2744 (Abstr.) Cohen, P. J., Marshall, B. E. 1968. Tox icity of Anesthetics, ed. B. R. Fink, Chap. 3, 24-36. Baltimore: Williams & Wilkins Cohen, P. J., Marshall, B. E., Lecky, B. A. 1969. Effects of halothane on mitochondrial oxygen uptake: site of ac tion. Anesthesiology 30:337 Cohen, P. J., McIntyre, R. A. 1972. Cel lular Biology and Toxicity of Anesthet ics, ed. B. R. Fink, Chap 10, 109-16. Baltimore: Williams & Wilkins. 328 pp. Hall, G. M., Kirtland, S. J., Baum, H. 1973. The inhibition of mitochondrial respiration by inhalational anaesthetic agents. Brit. J. Anaesth. 45: 1005-9 Harris, R. A., Munroe, J., Farmer, B., Kim, K. C., Jenkins, P. 1971. Action of halothane upon mitochondrial respira tion. Arch. Biochem. Biophys. 142: 435-44 Nahrwold, M. L., Cohen, P. J. 1973. The effects of forane and fluroxene on mitochondrial respiration. Anesthesi ology 39:437-44 Miller, R. N., Hunter, F. E. 1971. Is halothane a true uncoupler of oxidative phosphorylation? Anesthesiology 35: 256-61 Miller, R. N., Hunter, F. E. 1970. The effect of halothane on electron trans port, oxidative phosphorylation and swelling in rat liver mitochondria. Mol. Pharmacol. 6:67-77 See Ref. 41. 93-108 Miller, R. N., Schumer, W., Erve, P. R. 1972. The effects of halogenated anes thetics on mitochondrial function. Anesthesiology 36:625-27 Schumer, W., Erve, P. R., Obernolte, R. P., Bombeck, C. T., Sadove, M. S. 197 J. The effect of inhalation of haloge nated anesthetics on rat liver mitochon drial function. Anesthesiology 35: 253-55 Schumer, W., Erve, P. R., Obernolte, R. P., Bombeck, C. T., Sadove, M. S. 1972. Halogenated anesthetics' effect on rat liver mitochondria. Z. Exp. Chir. 5:\3-16 Michenfelder, J. D., Theye, R. A. 1972. Effects of cyclopropane on canine cere bral blood flow and metabolism. Anes thesiology 37:32-39 Michenfelder,1. D., Theye, R. A. 1973. Effects of methoxyflurane on canine
400
53.
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64. 65.
66.
BRUNNER, CHENG & BERMAN cerebral metabolism and blood flow. Anesthesiology 38: 123-27 Smith, A. L. 1973. The mechanism of cerebral vasodilation by halothane. Anesthesiology 39:581-87 Matteo, R. S., Hoech, G. P., Hoskin, F. C. G. 1969. Effects of cyclopropane and diethyl ether on tissue oxygen con sumption and anaerobic glycolysis of brain in vitro. Anesthesiology 30:15�3 Hoesin, E. A., Stachiewicz, E., Bourne, W., Demstedt, O. F. 1955. The influ ence of nitrous oxide on the metabolic activity of brain tissue. Anesthesiology 16:708-15 Biebuyck, J. F., Hawkins, R. A. 1972. The effect of anaesthetic agents on brain tissue metabolite patterns. Brit. J. Anaesth. 44:226-27 Brunner, E. A., Passonneau, J. V., Mol stad, C. 1971. The effect of volatile an aesthetics on levels of metabolites and on metabolic rate in brain. J. Neuro chem. 18:2301-16 Heim, F., Esteler, c.-J., Ammon, H. P.
T., Picker, D. 1966. Effect of trichloro
ethylene on brain levels of high energy phosphate, coenzyme A and glycolytic metabolites in white mice. Arch. Int. Pharmacodyn. Ther. 162:311-18 Nilsson, L., Siesjo, B. K. 1970. The effect of anesthetics upon labile phos phates and upon extra- and intra-cellu lar lactate, pyruvate and bicarbonate concentrations in the rat brain. Acta Physiol. Scand. 80:235.,.48 Goldberg, N. D., Passonneau, J. V., Lowry, O. H. 1966. The effects of changes in brain metabolism on the lev els of citric acid cycle intermediates. J. Bioi. Chem. 17:3997.,.4003 Doring, H. J., Olbrisch, R. R., Schrader, J., Lang, H. 1970. Electrocor ticograms, steady potential of the brain and energy-rich phosphate fractions of the cerebral cortex during anesthetic overdosage, ischemia and cyanide poi soning. Pjieuger S Arch. 319:12-35 Gatz, E. E., Schoettger, J. D., Morgan, J. R., Bird, J. S., Jones, J. R. 1971. Fed. Proc. 30:442 (Abstr. 1378) Gatz, E. E., Jones, J. R. 1969. Fed. Proc. 28:356 (Abstr. 353) Brody, T. M., Bain, J. A. 1954. Barbitu rates and oxidative phosphorylation. J. Pharmacol. Exp. Ther. 110:148-56 Smith, H. 1973. Effect of halothane upon rabbit brain mitochondria. Bio chem. Pharmacol. 22:773-81 Rosenberg, H., Haugaard, N. 1973. The effects of halothane on metabolism and
67.
68.
69.
70.
71.
72.
calcium uptake in mitochondria of the rat liver and brain. Anesthesiology 39:#-53 Miller, R. N., Miller, E., Caine, J., Sta bler, M. 1974. Synaptosomes, a possible system for the study of synaptic trans mission. Anesth. Analg. 53:132.,.41 Johnson, W. J., Quastel, J. H. 1953. A comparison of the effects of narcotics and 2,4-dinitrophenol on sulfanilamide acetylation. J. Biol Chem. 205:163-71 Cheng, S.-c., Brunner, E. A. 1975. Molecular Mechanisms of Anesthesia, ed. B. R. Fink. New York: Raven. In press Cremer, J. E., Lucas, H. M. 1971. Sodium pentobarbitone and metabolic compartments in rat brain. Brain Res. 35:619-21 Hakim, A. M., Moss, G. 1974. The effect of ether anesthesia on cerebral glucose metabolism-the pentose phos phate pathway. Anesthesiology 40: 261-67 Hassler, C., Hassler, R., Okada, Y., Bak,
73.
74.
75.
76.
77.
78.
79.
I.
J.
1971.
Pre-ictal
and
ictal
changes of serotonin, GABA and gluta mate contents in different regions of rabbit brain during methoxypyridoxine induced seizures. Acta Neurol. Lat inoamer. 17:595-611 Reynolds, A. P., Gallagher, B. B. 1973. The effect of hexafluorodiethyl ether (flurothyl) on the metabolism of rat brain amino acids labelled by (U-I.C) glucose. Life Sci. 13:87-95 Reynolds, A. P., Watkins, J. C. 1972. The effect of strychnine and of electrical stimulation on the labelling of 'Y aminobutyric acid and other free amino acids from (U-I'C) glucose in the spinal cord of the nembutalized rat. Brain Res. 36:343-51 Balazs, R., Cremer, J. E., 1973. Meta bolic Compartmentation in the Brain. London: Macmillan. 383 pp. Grewaal, D. S., Quastel, J. H. 1973. Control of synthesis and release of ra dioactive acetylcholine in brain slices from the rat. Biochem. J. 132:1-14 Sharkawi, M. 1970. Effects of morphine and pentobarbitone on acetylcholine synthesis by rat cerebral cortex. Brit. J. Pharmacol. 40:86-91 Sundwall, A. 1973. Effect of pentobar bital on the turnover of acetylcholine in brain nerve terminals in vivo. Brain Res. 62:531-36 Domino, E. F., Wilson, A. E. 1972. Psy chotropic drug influences on brain ace-
ANESTHESIA AND METABOLISM
80.
Annu. Rev. Med. 1975.26:391-401. Downloaded from www.annualreviews.org Access provided by University of Prince Edward Island on 02/07/15. For personal use only.
81.
82.
83.
84.
85.
86.
87.
tylcholine utilization. Psychopharmacologia 25:291-98 Jones, B. E., Guyenet, P., Cher�my, A., Gauchy, C., G1owinski, J. 1973 The in vivo release of acetylcholine flOm cat caudate nucleus after pharmacological and surgical manipulations of dopamin ergic nigrostriatal neurons. Brain Res. 64:355-69 Tappaz, P. M., Tacheco, H. 1973. Effects of convulsant and anticonvul sant drugs on the spontaneous and in duced release of GABA(14C) from cor tex slices of rat brain. J. Pharmacol. (Paris) 4:433-52 Cutler, R. W. P., Dudzinski, D. S. 1974. Effect of pentobarbital on uptake and release of (lH)GABA and (14C) gluta mate by brain slices. Brain Res. 67:546-48 Blagoeva, P., Longo, V. G., Masi, I., Scotti de Carolis, A. 1972. Alterations in behavior, EEG, and brain cortical GABA content following prolonged ad ministration and subsequent with drawal of barbital in the rat. Behav. Bioi. 7:755-60 Tsuji, H., Balagot, R. C., Sadove, M. S. 1963. Effect of anesthetics on brain gamma-aminobutyric and glutamic acid levels. J. Am. Med. Assoc. 183:659-61 Harris, M., Hopkin, J. M., Neal, M. J. 1973. Effect of centrally acting drugs on the uptake of y-aminobutyric acid (GABA) by slices of rat cerebral cortex. Brit. J. Pharmacol. 47:229-39 Chance, B., Cohen, P., 10bsis, F., Scho ener, B. 1962. Intracellular oxidation reduction states in vivo. Science 137:499-508 Merin, R. G. 1975. See Ref. 69
401
88. Cooperman, L. H. 1970. Plasma free fatty acid levels during general anes thesia and operation in man. Brit. J. Anaesth. 42:131-35 89. Tarhan, S., Fulton, R. E., Moffitt, E. A. 1971. Body metabolism during general anesthesia without superimposed surgi cal stress. Anesth. Analg. 50:915-23 90. Schotz, M. C., Olivecrona, T. 1966. The effect of anesthesia on the fate of in jected free fatty acid. Biochim. Biophys. Acta 125:174-75 91. Ishii, D. N., Corbascio, A. N. 1971. Some metabolic effects of halothane on mammalian tissue culture cells in vitro. Anesthesiology 35:427-38 92. Manku, R. S. 1970. Effect of anesthesia on protein metabolism in patients un dergoing hemioplasty. Anesth. Analg. 49:446-49 93. Kramer, M. F., Poort, C. 1972. Influ ence of anaesthetic drugs on amino acid incorporation in the rat pancreas. Bio chem. Pharmacol. 21:441-47 94. Ho, I. K., Keats, A. S. 1969. Effect of anesthetics on sulfhydryl content of rat brain. Pharmacology 2:257-64 95. Hinkley, R. E., Telser, A. G. 1974. See Ref. 69 96. Allison, A. C., Nunn, J. F. 1968. Effects of general anesthetics on microtubules: a possible mechanism of anesthesia. Lancet 3:1326--29 97. Sauberman, A. J., Gallagher, M. L. 1973. Mechanisms of general anes thesia: failure of pentobarbital and halo thane to depolymerize microtubules in mouse optic nerve. Anesthesiology 38:25-31 98. Wiklund, R. A., Allison, A. C. 1972. Effects of anaesthetics on the motility of Dictyostelium discoideum. Nature (New BioL) 239:221-22 .
