Effect of NH4CI on Plasma Aldosterone, Cortisol and Renin Activity in Supine Man GUIDO O. PEREZ, JAMES R. OSTER, CARLOS A. VAAMONDE, AND FRED H. KATZ Medical and Research Services, Veterans Administration Hospital, and Department of Medicine, University of Miami School of Medicine, Miami, Florida, and Medical Service, Veterans Administration Hospital, and Department of Medicine, University of Colorado School of Medicine, Denver, Colorado ABSTRACT. Plasma aldosterone, renin activity, cortisol and serum potassium were measured in six normal subjects before (control day) and during the oral administration of NH4C1 (1.9 meq/kg body weight). Blood samples were obtained with the subjects supine and fasting while in balance on a 10 meq sodium, 60 meq potassium diet. During the control day, 24 h urinary sodium excretion was 8 ± 3 (SE) meq and plasma aldosterone, renin activity and cortisol followed their expected diurnal variation. Following NH4CI (given between 0900 h and 1100 h), venous blood pH and serum bicarbonate concentrations decreased (P < 0.05 and P < 0.005, respectively) but the expected circadian decline in
plasma aldosterone did not occur and the values at 1200 h and 1600 h were higher (P < 0.05 and P < 0.02, respectively) than those of the control day. There were slight but not significant increases in plasma renin activity and serum potassium concentration. These observations indicate that plasma aldosterone increases in response to NH4C1. The observed changes may have been related to the combined effect of the slight increases in serum potassium and/or plasma renin activity. However, we can not exclude the possibility that acidosis per se, at least in part, stimulated an increased adrenal secretion of aldosterone. (J Clin Endocrinol Metab 45: 762, 1977)
I
N NORMAL man, acute administration of aldosterone or aldosterone-like steroids results in a reduction of urinary pH and an increase in the rate of urinary acid excretion (1,2). Aldosterone can also stimulate hydrogen ion secretion in the urinary bladder of the toad without demonstrable effects on sodium transport (3). Prolonged administration of desoxycorticosterone (4) and primary aldosteronism (5) are frequently associated with metabolic alkalosis. Furthermore, aldosterone deficiency is often associated with metabolic acidosis (6) and administration of aldosterone antagonists (7) results in an increase in urinary pH and a reduction in acid excretion. While aldosterone is known to influence acid-base homeostasis, there is limited information
Received February 7, 1977. Supported by a grant (RR00261) from the General Clinical Research Center Programs of the Division of Research Resources, National Institutes of Health, and by designated Veterans Administration research funds. Reprint requests to: Guido O. Perez, M.D., Chief, Dialysis Unit (111C), Veterans Administration Hospital, 1201 N.W. 16th Street, Miami, Florida 33125.
concerning the influence of acidifying agents on the adrenal secretion of aldosterone (8-10). Recently, Kisch et al. (8) demonstrated that iv ammonium chloride administration in man was associated (during a 1 h period) with a decline in plasma renin activity without a parallel decrement in plasma aldosterone concentration. The present study was designed to evaluate further the effects of acute NH4Cl-induced metabolic acidosis on plasma aldosterone concentration in man. The results demonstrate that plasma aldosterone increased in response to the acid load. The observed changes may have been mediated by the combined effect of slight changes in plasma renin activity and serum potassium concentration; however, we can not exclude the possibility that the results were due, at least in part, to changes in acid-base status. Materials and Methods Six healthy male volunteers between the ages of 20 and 25 years were studied at the Clinical Research Center of the University of Miami
762
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NH4C1 AND PLASMA ALDOSTERONE School of Medicine. All were normotensive, had normal physical examinations, gave no history of renal, adrenal, or cardiovascular disease and denied use of drugs. Urinalyses, blood urea nitrogen and serum electrolyte concentrations were normal. The subjects were maintained on their usual activity pattern and ate a constant 10-meq sodium, 60-meq potassium diet divided into three meals each day and a small snack at bedtime. A single dose of furosemide, 20 mg, was given by mouth on the morning of the first day. The subjects had access to unrestricted amounts of distilled water. Body weight and 24-h urinary sodium, potassium and creatinine were measured daily throughout the study. On the day following achievement of sodium balance (third or fourth day [control day]), blood was obtained for determination of serum potassium and plasma cortisol, renin activity and aldosterone at 2400 h, 0800 h, 1200 h and 1600 h. The subjects remained fasting and recumbent during this period except between 1600 h and 2200 h when they simulated their normal daily activities and ingested the prescribed diet. On the following day, the same protocol was followed except that each subject was given 1.9 meq/kg body weight of NH4C1 prepared in gelatin capsules and ingested with 200 ml of water over approximately 2-h (0900 h to 1100 h). Venous blood was obtained for pH and Pco2 measurements at 0800 h, prior to the acid load, and at 1200 h and 1600 h. The effects of NH4C1 loading on urinary acid excretion in five of these subjects have been reported elsewhere (11). Written informed consent was obtained after explanation of the details of the procedures and the potential risks. The research was carried out according to the principles outlined in the Declaration of Helsinki and was approved by the Human Experimentation Committees of the University of Miami School of Medicine and the Miami Veterans Administration Hospital. Plasma renin activity was measured by the method of Katzet al. (12) and plasma aldosterone concentration by a modification (13) of the method of Gomez-Sanchez et al. (14). Plasma cortisol was determined by a fluorometric method (15), sodium and potassium by flame photometry and creatinine by an automated method of chemical analysis. The data are presented as means ± SE and were evaluated by means of Student's t test.
763
Results As a result of the sodium restricted diet and furosemide administration, the subjects lost an average of 1.6 ±0.1 (SE) kg in weight (Table 1). On the day prior to acid loading, urinary sodium was 8 ± 3 meq/24-h and urinary potassium excretion was 53 ± 6 meq. The serum sodium, potassium and bicarbonate concentrations were within the normal range, except for a serum sodium of 134 meq/liter in subject 4. Creatinine clearance decreased an average of 15 ml/min as a result of sodium depletion. Acid loading resulted in significant decreases in venous pH (before NH4C1: 7.31 ± 0.01; after NH4C1: 7.26 ± 0.01; P < 0.05) and bicarbonate (before NH4C1: 28 ± 1; after NH4C1: 21 ± 1 meq/liter; P < 0.005). Changes in plasma aldosterone concentration, plasma renin activity, plasma cortisol and serum potassium in response to NH4Cl (Fig. 1, Table 2) During the course of the control day, plasma aldosterone concentration followed the expected circadian pattern (13,16,17) (Fig. 1), with the mean peak value occurring at 0800 h (261 ± 81 pg/ml). On the day of the acid load, the 2400 and 0800 h plasma aldosterone concentrations were not significantly different from those of the control day. Following administration of NH4C1, plasma aldosterone increased from 254 ± 73 pg/ml at 0800 h to 431 ± 71 pg/ml at 1200 h in contrast to the decrease seen on the control day. Both the 1200 and 1600 h values were significantly higher (P < 0.05 and P < 0.02, respectively) on the day of acid loading than on the control day. Plasma renin activity values at 0800, 1200 and 1600 h of the acid loading day did not differ significantly from the values of the control day. After NH4C1, the 1200 h value was slightly but not significantly higher than that of 0800 h, while on the control day the opposite occurred. Plasma cortisol levels showed the ex-
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764
JCE & M • 1977 Vol 45 • No 4
PEREZ ET AL.
TABLE 1. Laboratory findings in six healthy volunteers who underwent NH4C1 acid loading Effect of mild sodium depletion
Effect of NH4C1 loading Chan;»e in
Subject
s Na *
(meq/liter)
SK* (meq/liter)
1 2 3 4 5 6 x ± SE
138 142 141 134 135 142 139 ± 1
4.0 4.6 4.5 4.2 4.3 5.0 4.4 ± 0.1
Decrease in
(meq/24 h)
u K vt
(meq/24 h)
Body| weight (kg)
Ccr{ (ml/min)
Venous§ PH
Venous5 HCO3 (meq/liter)
UN,V" (meq/6 h)
CcrU (ml/min)
2 1 16 12 12 4 8±3
43 54 70 64 33 54 53 ± 6
2.0 1.4 1.7 1.5 1.5 1.6 1.6 + 0.1
20 18 16 10 28 0 15 ± 4
0.10 0.06 0 0.04 0.07 0.04 0.05 ± 0.01
9.1 6.1 7.7 3.2 10.6 5.9 7± 1
2 3 4 12 14 26 10 ±4
126 104 105 118 168 171 132 ± 12
u Na vt
* Obtained on the acid loading day prior to NH^Cl administration, t Values represent the 24-h period preceding acid load. I Decrement induced by sodium depletion (admission value minus that of acid loading day). § Decrements induced by acid loading. II Measured during the 6-h of the acid loading study (0900-1500 h). H Average of 3-5 collection periods during acid loading.
pected decline throughout the day in both studies, except for the 1600 h value on the day of acid loading. Serum potassium concentration did not change during the control day. During acid loading, there was a small but not statistically significant increase in serum potassium from 4.2 ±0.1 meq/liter at 0800 h to 4.4 ± 0.2 meq/liter at 1200 h. Except for the 2400 h values for serum potassium, both plasma cortisol and serum potassium levels during the acid loading day were not statistically different from those obtained during the control day. Serum sodium did not change significantly during any of the studies and the values of the control day were not different from those obtained during acid loading.
vious observations (13,16,17) of the existence of a diurnal variation of plasma aldosterone independent of posture, food and sodium intake. The physiologic mechanism(s) responsible for the observed changes in plasma aldosterone cannot be elucidated by these studies. It is possible that the changes could have been mediated by decreases in blood pH. Conversely, the combined effect of the slight increases observed in serum potassium concentration and plasma renin activity might have contributed to the observed changes in plasma aldosterone. Slight increases of serum potassium may be associated with significant increments of plasma aldosterone concentration (20). In the present study, the maximum increment Discussion in plasma aldosterone following acid loading Although mineralocorticoids have an im- was associated temporally with a mean inportant influence on acid-base homeo- crease (not statistically significant) in stasis (1-7), the possibility that acid-base serum potassium of 0.2 meq/liter, and acalterations influence aldosterone secretion cordingly it is possible that this increase has not been considered extensively (8-10, might have been responsible to some extent 18,19). The present observations demon- for the increments in plasma aldosterone strate that acute NH4C1 acid loading in man observed. On the other hand, if intracellular increases plasma aldosterone. Such a hor- potassium concentration is a major factor monal response might promote acid excre- regulating the biosynthesis of aldosterone tion by the kidney thus helping to maintain (21), a decrease in plasma aldosterone and restore acid-base equilibrium. In might have been anticipated since extraaddition, the present study confirms pre- cellular acidemia is believed to result in a
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765
NH4C1 AND PLASMA ALDOSTERONE
O O CO rH
Plasma 400 Aldosterone (pg/ml) 200
5 Serum Potassium 4 (meq/L) ,
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m
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240
FIG. 1. Changes in plasma aldosterone, renin activity, as """" cortisol and potassium on the day prior to ( — O — ) and on the day of acid loading ( — • — ). The probaE£ bility values depicted on the figure refer to comparisons between the control and experimental days. •3.JJ There were no statistically significant differences for the intradiem values within the experimental and control days for plasma aldosterone, plasma renin -§5 activity, and serum potassium concentration, except for the 1200 h plasma aldosterone value on the experimental day which was higher (P < 0.05) than the 2400 h value. The 0800 h plasma cortisol values were higher than the 2400 h values (Control: P < 0.005; .5"* acid loading: P < 0.001), and the 1200 h values lower than the 0800 h values (Control: P < 0.05; acid loading: P < 0.001), while the 1600 h values were not significantly different from the 1200 h values.
O5 TP CO -H 00 in O5 -H
CO CD 00 O CD -H TP in
T—1
1E
-C
"ab o
3
o (N
1
m
in
rp CD CO CO CO CD
_< 00 CN CO
o to in
CO l> O CD lO '"sP O5 O "-•
c o u ID in O
shift of potassium from the intracellular to the extracellular space (22). Acid loading may be associated with a negative sodium balance (23). In the present study, however, the increase in plasma renin activity following acid loading was minor and not statistically significant, sug-
120
(mec en tn cS O OH
•
Plasma Cortisol 10 (|ig/100ml)
1 O5
1TP
0.7
20r
O CO in co
00 00 in in TP TP CO TP rp
E
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(N
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0 Plasma 16 Renin Activity (ng/ml/fir) t
o
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766
JCE & M • 1977 Vol 45 • No 4
PEREZ ET AL.
gesting that important changes of extracellular fluid volume did not occur. Urinary sodium during the 6 h of the acid loading study averaged 10 ± 4 meq (Table 1), a value similar to the excretion of sodium during the day preceding acid loading. On the other hand, Kisch et al. (8) recently have demonstrated that a 1 h iv infusion of NH4C1 may be associated with significant suppression of plasma renin activity. Such a suppression might thus have masked any influence of volume contraction on plasma renin activity in the present study. Of interest, a dissociation between the renin and aldosterone responses (plasma aldosterone levels not changing) was noted in the study of Kisch et al. (8), but these investigators were unable to conclude whether the lack of parallel suppression in plasma aldosterone was secondary to acidosis, NH4+, or Cl~ or to a non-specific stress reaction, since plasma cortisol levels also tended to rise. It is possible that the conflict between the data of Kisch et al. (8) and the present studies are due to differences in experimental design. Our sampling at 4-h intervals may have missed acute and short-lived changes in plasma renin activity or plasma cortisol. The effect of acidosis on plasma renin activity has been evaluated in two recent studies in the dog (24,25). The studies, however, did not provide data on aldosterone. The results of a previous study in experimental animals (26) suggest that marked extracellular fluid acidosis is accompanied by increases in the adrenal secretion of 17-OH corticosteroids. It is important to point out that in the present study plasma cortisol levels were not increased at the time of peak plasma aldosterone levels or at any time during the study. Thus, an increase in ACTH secretion did not appear to have mediated the plasma aldosterone response. Muller (9) reported that ammonium and other monovalent cations stimulated aldosterone production by adrenal slices from rats which have been kept on a sodium
restricted diet for two weeks. Blair-West et al. (10) infused NH4C1 into the adrenal blood supply of conscious sheep with autotransplanted adrenal glands. At rates of infusion calculated to increase ammonia concentration by 1 meq/liter or more, aldosterone secretion increased significantly. Since in normal subjects NH4C1 loading results in minimal increases in blood ammonia (27,28) and the concentration of ammonium utilized by Muller (7.7 mmol/liter) and Blair-West et al. (>1 meq/liter) was at least ten times the normal blood level, it is unlikely that the results obtained in the present study were due to an aldosterone stimulating effect of the ammonium ion per se. In conclusion, the present findings indicate that short duration NH4C1 acid loading is associated with increased levels of plasma aldosterone. Although it is possible that the increases in plasma aldosterone were mediated by the combined influences of small increases in serum potassium concentration and plasma renin activity, we cannot exclude the possibility that acidosis per se was, at least in part, responsible. Acknowledgments We are indebted to Ellen Roper, Jo Anne Hansen, Diane Loeffel and Barbara Reitberg for the hormonal measurements and to Genaro Rodriguez, Robert Rubin, Kenneth Bailey and Charlene Morgan for their assistance. The studies were performed in part at the Clinical Research Center, University of Miami School of Medicine.
References 1. Mills, J. N., S. Thomas, and K. S. Williamson, The acute effect of hydrocortisone, deoxycorticosterone and aldosterone upon the excretion of sodium, potassium and acid by the human kidney, J Physiol 151: 312, 1960. 2. Bartter, F. C , and P. Fourman, The different effects of aldosterone-like steroids and hydrocortisone-like steroids on urinary excretion of potassium and acid, Metabolism 11: 6, 1962. 3. Ludens, J. H., and D. D. Fanestil, Aldosterone stimulation of acidification of urine by isolated urinary bladder of the Colombian toad, Am J Physiol 226: 1321, 1974. 4. Roth, D. G., and J. L. Gamble, Jr., Deoxycorti-
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NH4C1 AND PLASMA ALDOSTERONE
5. 6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
costerone-induced alkalosis in dogs, J Physiol 208: 90, 1965. Conn, J. W., Primary aldosteronism, J Lab Clin Med 45: 661, 1955. Perez, G. O., J. R. Oster, and C. A. Vaamonde, Renal acidosis and renal potassium handling in selective hypoaldosteronism, Am J Med 57: 809, 1974. Manuel, M. A., G. J. Beirne, J. P. Wagnild, and M. W. Weiner, An effect of spironolactone on urinary acidification in normal man, Arch Intern Med 134: 472, 1974. Kisch, E. S., R. G. Dluhy, and G. H. Williams, Regulation of renin release by calcium and ammonium ions in normal man, / Clin Endocrinol Metab 43: 1343, 1976. Muller, J., Aldosterone stimulation in vitro. II. stimulation of aldosterone production by monovalent cations, Ada Endocrinol (Kbh) 50: 301, 1965. Blair-West, J. R., J. P. Coghlan, D. A. Denton, J. R. Goding, M. Wintour, and R. D. Wright, The local action of ammonium, calcium and magnesium on adrenocortical secretion, Aust J Exp Biol Med Sci 46: 371, 1968. Perez, G. O., J. R. Oster, and C. A. Vaamonde, The effect of sodium depletion on the renal response to short-duration NH4C1 acid loading, Proc Soc Exp Biol Med 154: 562, 1977. Katz, F. H., and J. A. Smith, Radioimmunoassay of angiotensin I: Comparison of two renin activity methods and use for other measurements of the renin system, Clin Chein 18: 528, 1972. Katz, F. H., P. E. Romfh, and J. A. Smith, Diurnal variation of plasma aldosterone, cortisol and renin activity in supine man, J Clin Endocrinol Metab 40: 125, 1975. Gomez-Sanchez, C , D. C. Kem, and N. M. Kaplan, A radioimmunoassay for plasma aldosterone by immunologic purification,/ Clin Endocrinol Metab 36: 795, 1973. Mattingly, D., A simple fluorometric method for the estimation of free 11-hydroxycorticoids in human plasma, 7 Clin Pathol 15: 374, 1962. Michelakis, A. M., and R. Horton, The relationship between plasma renin and aldosterone in
17.
18.
19.
20. 21.
22.
23.
24. 25. 26. 27.
28.
767
normal man, Circ Res (Suppl 1) 26-27: 1-185, 1970. Vagnucci, A. H., R. H. McDonald, A. L. Drash, and A. K. C. Wrong, Intradiem changes of plasma aldosterone, cortisol, corticosterone and growth hormone in sodium restriction,/ Clin Endocrinol Metab 38: 761, 1974. Kassirer, J. P., F. M. Appleton, J. A. Chazan, and W. B. Schwartz, Aldosterone in metabolic alkalosis, J Clin Invest 46: 1558, 1967. Cohen, J. J., H. N. Hulter, N. Smithline, J. C. Melby, and W. B. Schwartz, The critical role of the adrenal gland in the renal regulation of acidbase equilibrium during chronic hypotonic expansion. Evidence that chronic hyponatremia is a potent stimulus to aldosterone secretion, / Clin Invest 58: 1201, 1976. Himathongkam, T., R. G. Dluhy, and G. H. Williams, Potassium-aldosterone-renin interrelationships,/ Clin Endocrinol Metab 41: 153, 1975. Baumber, J. S., J. O. Davis, J. A. Johnson, and R. T. Witty, Increased adrenocortical potassium in association with increased biosynthesis of aldosterone, Am] Physiol 220: 1094, 1971. Orloff, J., T. J. Kennedy, Jr., and R. W. Berliner, The effect of potassium in nephrectomized rats with hypokalemic alkalosis,/ Clin Invest 23: 538, 1953. Clarke, E., B. M. Evans, I. Maclntyre, and M. D. Milne, Acidosis in experimental electrolyte depletion, Clin Sci 14: 421, 1955. Lifschitz, M. D., and L. E. Earley, An intrarenal effect of blood pH on the release of renin, / Clin Invest 53: 47a, 1974. Morita, T., Plasma renin activity in acute respiratory acidosis, Jap Circ J 40: 123, 1976. Richards, J. B., Effects of altered acid-base balance on adrenocortical function in anesthetized dogs, AmJ Physiol 188: 7, 1957. Conn, H. O., Studies of the source and significance of blood ammonia. Early ammonia peaks after ingestion of ammonium salts, Yale J Biol Med 45: 543, 1972. Owen, E. E., and R. R. Robinson, Amino acid extraction and ammonia metabolism by the human kidney during the prolonged administration of ammonium chloride,/ Clin Invest 42: 263, 1963.
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plasma aldosterone did not occur and the values at 1200 h and 1600 h were higher (P < 0.05 and P < 0.02, respectively) than those of the control day. There were slight but not significant increases in plasma renin activity and serum potassium concentration. These observations indicate that plasma aldosterone increases in response to NH4C1. The observed changes may have been related to the combined effect of the slight increases in serum potassium and/or plasma renin activity. However, we can not exclude the possibility that acidosis per se, at least in part, stimulated an increased adrenal secretion of aldosterone. (J Clin Endocrinol Metab 45: 762, 1977)
I
N NORMAL man, acute administration of aldosterone or aldosterone-like steroids results in a reduction of urinary pH and an increase in the rate of urinary acid excretion (1,2). Aldosterone can also stimulate hydrogen ion secretion in the urinary bladder of the toad without demonstrable effects on sodium transport (3). Prolonged administration of desoxycorticosterone (4) and primary aldosteronism (5) are frequently associated with metabolic alkalosis. Furthermore, aldosterone deficiency is often associated with metabolic acidosis (6) and administration of aldosterone antagonists (7) results in an increase in urinary pH and a reduction in acid excretion. While aldosterone is known to influence acid-base homeostasis, there is limited information
Received February 7, 1977. Supported by a grant (RR00261) from the General Clinical Research Center Programs of the Division of Research Resources, National Institutes of Health, and by designated Veterans Administration research funds. Reprint requests to: Guido O. Perez, M.D., Chief, Dialysis Unit (111C), Veterans Administration Hospital, 1201 N.W. 16th Street, Miami, Florida 33125.
concerning the influence of acidifying agents on the adrenal secretion of aldosterone (8-10). Recently, Kisch et al. (8) demonstrated that iv ammonium chloride administration in man was associated (during a 1 h period) with a decline in plasma renin activity without a parallel decrement in plasma aldosterone concentration. The present study was designed to evaluate further the effects of acute NH4Cl-induced metabolic acidosis on plasma aldosterone concentration in man. The results demonstrate that plasma aldosterone increased in response to the acid load. The observed changes may have been mediated by the combined effect of slight changes in plasma renin activity and serum potassium concentration; however, we can not exclude the possibility that the results were due, at least in part, to changes in acid-base status. Materials and Methods Six healthy male volunteers between the ages of 20 and 25 years were studied at the Clinical Research Center of the University of Miami
762
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NH4C1 AND PLASMA ALDOSTERONE School of Medicine. All were normotensive, had normal physical examinations, gave no history of renal, adrenal, or cardiovascular disease and denied use of drugs. Urinalyses, blood urea nitrogen and serum electrolyte concentrations were normal. The subjects were maintained on their usual activity pattern and ate a constant 10-meq sodium, 60-meq potassium diet divided into three meals each day and a small snack at bedtime. A single dose of furosemide, 20 mg, was given by mouth on the morning of the first day. The subjects had access to unrestricted amounts of distilled water. Body weight and 24-h urinary sodium, potassium and creatinine were measured daily throughout the study. On the day following achievement of sodium balance (third or fourth day [control day]), blood was obtained for determination of serum potassium and plasma cortisol, renin activity and aldosterone at 2400 h, 0800 h, 1200 h and 1600 h. The subjects remained fasting and recumbent during this period except between 1600 h and 2200 h when they simulated their normal daily activities and ingested the prescribed diet. On the following day, the same protocol was followed except that each subject was given 1.9 meq/kg body weight of NH4C1 prepared in gelatin capsules and ingested with 200 ml of water over approximately 2-h (0900 h to 1100 h). Venous blood was obtained for pH and Pco2 measurements at 0800 h, prior to the acid load, and at 1200 h and 1600 h. The effects of NH4C1 loading on urinary acid excretion in five of these subjects have been reported elsewhere (11). Written informed consent was obtained after explanation of the details of the procedures and the potential risks. The research was carried out according to the principles outlined in the Declaration of Helsinki and was approved by the Human Experimentation Committees of the University of Miami School of Medicine and the Miami Veterans Administration Hospital. Plasma renin activity was measured by the method of Katzet al. (12) and plasma aldosterone concentration by a modification (13) of the method of Gomez-Sanchez et al. (14). Plasma cortisol was determined by a fluorometric method (15), sodium and potassium by flame photometry and creatinine by an automated method of chemical analysis. The data are presented as means ± SE and were evaluated by means of Student's t test.
763
Results As a result of the sodium restricted diet and furosemide administration, the subjects lost an average of 1.6 ±0.1 (SE) kg in weight (Table 1). On the day prior to acid loading, urinary sodium was 8 ± 3 meq/24-h and urinary potassium excretion was 53 ± 6 meq. The serum sodium, potassium and bicarbonate concentrations were within the normal range, except for a serum sodium of 134 meq/liter in subject 4. Creatinine clearance decreased an average of 15 ml/min as a result of sodium depletion. Acid loading resulted in significant decreases in venous pH (before NH4C1: 7.31 ± 0.01; after NH4C1: 7.26 ± 0.01; P < 0.05) and bicarbonate (before NH4C1: 28 ± 1; after NH4C1: 21 ± 1 meq/liter; P < 0.005). Changes in plasma aldosterone concentration, plasma renin activity, plasma cortisol and serum potassium in response to NH4Cl (Fig. 1, Table 2) During the course of the control day, plasma aldosterone concentration followed the expected circadian pattern (13,16,17) (Fig. 1), with the mean peak value occurring at 0800 h (261 ± 81 pg/ml). On the day of the acid load, the 2400 and 0800 h plasma aldosterone concentrations were not significantly different from those of the control day. Following administration of NH4C1, plasma aldosterone increased from 254 ± 73 pg/ml at 0800 h to 431 ± 71 pg/ml at 1200 h in contrast to the decrease seen on the control day. Both the 1200 and 1600 h values were significantly higher (P < 0.05 and P < 0.02, respectively) on the day of acid loading than on the control day. Plasma renin activity values at 0800, 1200 and 1600 h of the acid loading day did not differ significantly from the values of the control day. After NH4C1, the 1200 h value was slightly but not significantly higher than that of 0800 h, while on the control day the opposite occurred. Plasma cortisol levels showed the ex-
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764
JCE & M • 1977 Vol 45 • No 4
PEREZ ET AL.
TABLE 1. Laboratory findings in six healthy volunteers who underwent NH4C1 acid loading Effect of mild sodium depletion
Effect of NH4C1 loading Chan;»e in
Subject
s Na *
(meq/liter)
SK* (meq/liter)
1 2 3 4 5 6 x ± SE
138 142 141 134 135 142 139 ± 1
4.0 4.6 4.5 4.2 4.3 5.0 4.4 ± 0.1
Decrease in
(meq/24 h)
u K vt
(meq/24 h)
Body| weight (kg)
Ccr{ (ml/min)
Venous§ PH
Venous5 HCO3 (meq/liter)
UN,V" (meq/6 h)
CcrU (ml/min)
2 1 16 12 12 4 8±3
43 54 70 64 33 54 53 ± 6
2.0 1.4 1.7 1.5 1.5 1.6 1.6 + 0.1
20 18 16 10 28 0 15 ± 4
0.10 0.06 0 0.04 0.07 0.04 0.05 ± 0.01
9.1 6.1 7.7 3.2 10.6 5.9 7± 1
2 3 4 12 14 26 10 ±4
126 104 105 118 168 171 132 ± 12
u Na vt
* Obtained on the acid loading day prior to NH^Cl administration, t Values represent the 24-h period preceding acid load. I Decrement induced by sodium depletion (admission value minus that of acid loading day). § Decrements induced by acid loading. II Measured during the 6-h of the acid loading study (0900-1500 h). H Average of 3-5 collection periods during acid loading.
pected decline throughout the day in both studies, except for the 1600 h value on the day of acid loading. Serum potassium concentration did not change during the control day. During acid loading, there was a small but not statistically significant increase in serum potassium from 4.2 ±0.1 meq/liter at 0800 h to 4.4 ± 0.2 meq/liter at 1200 h. Except for the 2400 h values for serum potassium, both plasma cortisol and serum potassium levels during the acid loading day were not statistically different from those obtained during the control day. Serum sodium did not change significantly during any of the studies and the values of the control day were not different from those obtained during acid loading.
vious observations (13,16,17) of the existence of a diurnal variation of plasma aldosterone independent of posture, food and sodium intake. The physiologic mechanism(s) responsible for the observed changes in plasma aldosterone cannot be elucidated by these studies. It is possible that the changes could have been mediated by decreases in blood pH. Conversely, the combined effect of the slight increases observed in serum potassium concentration and plasma renin activity might have contributed to the observed changes in plasma aldosterone. Slight increases of serum potassium may be associated with significant increments of plasma aldosterone concentration (20). In the present study, the maximum increment Discussion in plasma aldosterone following acid loading Although mineralocorticoids have an im- was associated temporally with a mean inportant influence on acid-base homeo- crease (not statistically significant) in stasis (1-7), the possibility that acid-base serum potassium of 0.2 meq/liter, and acalterations influence aldosterone secretion cordingly it is possible that this increase has not been considered extensively (8-10, might have been responsible to some extent 18,19). The present observations demon- for the increments in plasma aldosterone strate that acute NH4C1 acid loading in man observed. On the other hand, if intracellular increases plasma aldosterone. Such a hor- potassium concentration is a major factor monal response might promote acid excre- regulating the biosynthesis of aldosterone tion by the kidney thus helping to maintain (21), a decrease in plasma aldosterone and restore acid-base equilibrium. In might have been anticipated since extraaddition, the present study confirms pre- cellular acidemia is believed to result in a
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765
NH4C1 AND PLASMA ALDOSTERONE
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240
FIG. 1. Changes in plasma aldosterone, renin activity, as """" cortisol and potassium on the day prior to ( — O — ) and on the day of acid loading ( — • — ). The probaE£ bility values depicted on the figure refer to comparisons between the control and experimental days. •3.JJ There were no statistically significant differences for the intradiem values within the experimental and control days for plasma aldosterone, plasma renin -§5 activity, and serum potassium concentration, except for the 1200 h plasma aldosterone value on the experimental day which was higher (P < 0.05) than the 2400 h value. The 0800 h plasma cortisol values were higher than the 2400 h values (Control: P < 0.005; .5"* acid loading: P < 0.001), and the 1200 h values lower than the 0800 h values (Control: P < 0.05; acid loading: P < 0.001), while the 1600 h values were not significantly different from the 1200 h values.
O5 TP CO -H 00 in O5 -H
CO CD 00 O CD -H TP in
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shift of potassium from the intracellular to the extracellular space (22). Acid loading may be associated with a negative sodium balance (23). In the present study, however, the increase in plasma renin activity following acid loading was minor and not statistically significant, sug-
120
(mec en tn cS O OH
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Plasma Cortisol 10 (|ig/100ml)
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766
JCE & M • 1977 Vol 45 • No 4
PEREZ ET AL.
gesting that important changes of extracellular fluid volume did not occur. Urinary sodium during the 6 h of the acid loading study averaged 10 ± 4 meq (Table 1), a value similar to the excretion of sodium during the day preceding acid loading. On the other hand, Kisch et al. (8) recently have demonstrated that a 1 h iv infusion of NH4C1 may be associated with significant suppression of plasma renin activity. Such a suppression might thus have masked any influence of volume contraction on plasma renin activity in the present study. Of interest, a dissociation between the renin and aldosterone responses (plasma aldosterone levels not changing) was noted in the study of Kisch et al. (8), but these investigators were unable to conclude whether the lack of parallel suppression in plasma aldosterone was secondary to acidosis, NH4+, or Cl~ or to a non-specific stress reaction, since plasma cortisol levels also tended to rise. It is possible that the conflict between the data of Kisch et al. (8) and the present studies are due to differences in experimental design. Our sampling at 4-h intervals may have missed acute and short-lived changes in plasma renin activity or plasma cortisol. The effect of acidosis on plasma renin activity has been evaluated in two recent studies in the dog (24,25). The studies, however, did not provide data on aldosterone. The results of a previous study in experimental animals (26) suggest that marked extracellular fluid acidosis is accompanied by increases in the adrenal secretion of 17-OH corticosteroids. It is important to point out that in the present study plasma cortisol levels were not increased at the time of peak plasma aldosterone levels or at any time during the study. Thus, an increase in ACTH secretion did not appear to have mediated the plasma aldosterone response. Muller (9) reported that ammonium and other monovalent cations stimulated aldosterone production by adrenal slices from rats which have been kept on a sodium
restricted diet for two weeks. Blair-West et al. (10) infused NH4C1 into the adrenal blood supply of conscious sheep with autotransplanted adrenal glands. At rates of infusion calculated to increase ammonia concentration by 1 meq/liter or more, aldosterone secretion increased significantly. Since in normal subjects NH4C1 loading results in minimal increases in blood ammonia (27,28) and the concentration of ammonium utilized by Muller (7.7 mmol/liter) and Blair-West et al. (>1 meq/liter) was at least ten times the normal blood level, it is unlikely that the results obtained in the present study were due to an aldosterone stimulating effect of the ammonium ion per se. In conclusion, the present findings indicate that short duration NH4C1 acid loading is associated with increased levels of plasma aldosterone. Although it is possible that the increases in plasma aldosterone were mediated by the combined influences of small increases in serum potassium concentration and plasma renin activity, we cannot exclude the possibility that acidosis per se was, at least in part, responsible. Acknowledgments We are indebted to Ellen Roper, Jo Anne Hansen, Diane Loeffel and Barbara Reitberg for the hormonal measurements and to Genaro Rodriguez, Robert Rubin, Kenneth Bailey and Charlene Morgan for their assistance. The studies were performed in part at the Clinical Research Center, University of Miami School of Medicine.
References 1. Mills, J. N., S. Thomas, and K. S. Williamson, The acute effect of hydrocortisone, deoxycorticosterone and aldosterone upon the excretion of sodium, potassium and acid by the human kidney, J Physiol 151: 312, 1960. 2. Bartter, F. C , and P. Fourman, The different effects of aldosterone-like steroids and hydrocortisone-like steroids on urinary excretion of potassium and acid, Metabolism 11: 6, 1962. 3. Ludens, J. H., and D. D. Fanestil, Aldosterone stimulation of acidification of urine by isolated urinary bladder of the Colombian toad, Am J Physiol 226: 1321, 1974. 4. Roth, D. G., and J. L. Gamble, Jr., Deoxycorti-
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NH4C1 AND PLASMA ALDOSTERONE
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normal man, Circ Res (Suppl 1) 26-27: 1-185, 1970. Vagnucci, A. H., R. H. McDonald, A. L. Drash, and A. K. C. Wrong, Intradiem changes of plasma aldosterone, cortisol, corticosterone and growth hormone in sodium restriction,/ Clin Endocrinol Metab 38: 761, 1974. Kassirer, J. P., F. M. Appleton, J. A. Chazan, and W. B. Schwartz, Aldosterone in metabolic alkalosis, J Clin Invest 46: 1558, 1967. Cohen, J. J., H. N. Hulter, N. Smithline, J. C. Melby, and W. B. Schwartz, The critical role of the adrenal gland in the renal regulation of acidbase equilibrium during chronic hypotonic expansion. Evidence that chronic hyponatremia is a potent stimulus to aldosterone secretion, / Clin Invest 58: 1201, 1976. Himathongkam, T., R. G. Dluhy, and G. H. Williams, Potassium-aldosterone-renin interrelationships,/ Clin Endocrinol Metab 41: 153, 1975. Baumber, J. S., J. O. Davis, J. A. Johnson, and R. T. Witty, Increased adrenocortical potassium in association with increased biosynthesis of aldosterone, Am] Physiol 220: 1094, 1971. Orloff, J., T. J. Kennedy, Jr., and R. W. Berliner, The effect of potassium in nephrectomized rats with hypokalemic alkalosis,/ Clin Invest 23: 538, 1953. Clarke, E., B. M. Evans, I. Maclntyre, and M. D. Milne, Acidosis in experimental electrolyte depletion, Clin Sci 14: 421, 1955. Lifschitz, M. D., and L. E. Earley, An intrarenal effect of blood pH on the release of renin, / Clin Invest 53: 47a, 1974. Morita, T., Plasma renin activity in acute respiratory acidosis, Jap Circ J 40: 123, 1976. Richards, J. B., Effects of altered acid-base balance on adrenocortical function in anesthetized dogs, AmJ Physiol 188: 7, 1957. Conn, H. O., Studies of the source and significance of blood ammonia. Early ammonia peaks after ingestion of ammonium salts, Yale J Biol Med 45: 543, 1972. Owen, E. E., and R. R. Robinson, Amino acid extraction and ammonia metabolism by the human kidney during the prolonged administration of ammonium chloride,/ Clin Invest 42: 263, 1963.
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