ASCORBIC ACID REQUIREMENTS AND METABOLISM IN RELATION TO ORGANOCHLORINE PESTICIDES * J. C. Street and R. W. Chadwick Department of Animal Science and Chemistry-Biochemistry Utah State University Logan, Utah 84322 and Pesticides and Toxic Effects Laboratory National Environmental Research Center Environmental Protection Agency Research Triangle Park, North Carolina 27711
Organochlorine pesticides, typified by DDT, Dieldrin, Lindane and some other well known insecticides, are normally in vivo substrates of drug metabolising enzymes including the monooxygenase and conjugating systems. Their metabolism, and hence toxicity, is subject to many factors known to influence these enzymes, including the animal’s nutritional state. The ascorbic acid status is one well established factor in that respect.l 3 Some organochlorine pesticides, including those already named, are potent “inducers” of the hepatic microsomal drug metabolising Such “induction” is recognized as an important adaptive process in animals and markedly influences the toxic expression of the inducing agent. Stimulation of the glucuronic pathway resulting in enhanced ascorbic acid biosynthesis has been known for many years and utilized as an index of inducer activity.”, 7 In early study of metabolic interaction among organochlorine pesticides we began to monitor ascorbic acid excretion in urine of the rats used in those studies since the interaction was believed to result from hepatic microsomal enzyme induction. Certain organochlorine pesticides such as DDT (FIGURE 1) were found to greatly stimulate ascorbic acid output soon after administration. With continued DDT administration the animals maintained twofold or greater ascorbic acid excretion for nearly six weeksx In contrast the insecticide methoxychlor, a very poor inducer, did not affect ascorbic acid excretion although administered at a level 10 times greater than DDT. These data were interpreted as indicating induction of microsomal enzyme activities by DDT as aminopyrine and heptabarbital, well known inducing agents, produced similar effects. Stimulation of the glucuronic acid pathway by organochlorine inducing agents is also indicated by enhanced excretion of glucuronic acid (FIGURE 2). Both DDT and Lindane (7-HCH) stimulated glucuronic acid excretion by rats but Lindane was considerably more potent.!’ That difference probably results from the fact that Lindane is metabolized to a number of chlorinated phenols which are excreted as glucuronides. The analyses represented in FIGURE 2 are for total glucuronic acid in urine, thus including glucuronide conjugates. These insecticides were also shown to produce similar effects upon glucuronic acid excretion by the squirrel monkey.’”
* The research was aided by USDA regional research funds, USPHS research and training grants ES-00255and GM-1179, and the Utah Community Studies Pesticide Project under contract with the Environmental Protection Agency. 132
Street & Chadwick: Pesticides and Vitamin C
133
Guinea pigs treated similarly with DDT or Lindane also displayed enhanced activity of the glucuronic acid pathway, evident as enhanced glucaric acid excretion (FIGURE 3).11 The data in FIGURE 3 represent groups of female guinea pigs treated in each case but the control with 50 pprn DDT plus 50 ppm Lindane. Enhanced glucaric acid excretion was obtained when the insecticides were administered in a diet containing soy protein or casein, but soy protein supported a much greater response. Gelatin, a poor quality protein, did not support statistically significant increases in glucaric acid excretion. These data,
FIGURL 1. Urinary ascorbic acid excretion by rats administered drugs and organochlorine insecticides in the diet. Commercial laboratory diets containing 50 ppm DDT, 500 pprn methoxychlor, 2000 ppm aminopyrine, 2000 ppm heptabarbital, and 5000 ppm tolbutamide, respectively, were fed to groups of female rats for 8 weeks. Diet intakes were not equalized, however, the ad libitum intakes were not statistically different among groups. Data from Chadwick.*
therefore, whilc confirming that DDT and Lindane stimulate the glucuronic acid pathway, also suggest that protein quality factors influence the enzyme responses obtained. Soy protein in this study gave results, relative to casein, similar to those obtained with female rats in induction experiments.'* A relatively lower response of induced animals upon the casein diet deficient in ascorbic acid was noted in comparison to the normal casein diet. That difference indicates a dependency upon ascorbic acid for the enzyme induction response to develop in the presence of organochlorine pesticide. The data in Frcum 4 support the
Annals New York Academy of Sciences
134
A V E R A P E h I O U N l S (in mg) O F P L U C U R O I I C A C I D E X C A C l E D P E R 24 HOURS VS T I M E ( i n d r y s ) . u
FIGURE 2. Effect of DDT, Lindane and their combination administered i.p. in peanut oil (2 mg of each) to female rats upon urinary glucuronic acid excretion. Dosing was made on day 0. (From Chadwick ct a/? By permission of Toxicology rind Applied Pharmacology. )
conclusion that the enhanced glucaric acid excretion in this species correctly indicated enhanced microsomal enzyme function. Pesticide administration generally resulted in increased cytochrome P-450,and greater hydrolysis of EPN, 0-demethylation of p-nitroanisole, and glucuronide formation from p-nitrophenol. However, ascorbic-acid-deficient animals displayed lower hepatic microsomal enzyme parameters, in comparison to the ascorbic-acid-normal casein group, in all but glucuronyl transferase activity. The absolute comparative responses were somewhat confounded by variable weight gains resulting from the ascorbic acid or protein deficiencies produced by certain diets. Just as the efficiency of drug metabolism is subject to the ascorbic acid status, there is evidence that pesticide degradation and elimination is also impaired by vitamin C deficiency. Correspondingly greater insecticide residue accumulation in tissues results which would be expected to aggravate the chronic toxic effects of the pesticides. The data in FIGURE5 illustrate this relationship in terms of Lindane (7-HCH) metabolism and excretion. The guinea pigs represented in this figure were being continuously treated with 50 ppm DDT plus 50 ppm Lindane in their diets to obtain microsomal enzyme induction. Between the directly comparable pair of treatments, those animals on an ascorbic-acid-free casein diet excreted less than half the total amount of Lindane metabolites as did those on a casein diet sufficient in ascorbic acid. The tissue
Street & Chadwick: Pesticides and Vitamin C
135
residues of Lindane would be proportionately higher in the vitamin-C-deficient guinea pigs. Poor quality proteins in the guinea pig diet potentiated the excretion of Lindane metabolites, a result of the enhanced hepatic microsomal enzyme activities obtained in those cases. Such effects of ascorbic acid deficiency presumably should occur in the primates, including man. Chadwick et a1.l" carried out one short-term experiment with female squirrel monkeys attempting to show effects of an inducing pesticide (DDT) and ascorbic acid deficiency on microsomal enzyme activities and Lindane metabolism. Their findings failed to show significant effects of vitamin C deficiency, except for impaired induction of 0-demethylation activity (FIGURE 6). However trends toward greater induced enzyme activities with supplemental vitamin C were apparent. Lindane metabolism, and consequently its storage in tissue, were not significantly affected by the ascorbate status in that 1). Since the monkeys wcrc only 15 days into ascorbic acid cxperiment (TABLE depletion when examined, the experimental period may have been insufficient to establish greatly altered conditions. Nevertheless, it might be concluded that the trends observed were sufficient to indicate that the general effects in this species are similar to those observed in the guinea pigs. The capacity of the liver to adapt to the presence of inducing agents such as DDT and Lindane through enhanced microsomal enzymatic levels appears to
2.0
-
2
5
-....... -------
CONTROL
1.6
-
---a-
ASCORBIC AClb DEFICIENT CASEIN SOY PROTEIN
cy \
P
GELATIN
V
4
u
GLUCARIC ACID EXCRETION
1.2
-
a
A
12
TIME (in doyr)
FIGURL 3. Urinary glucaric acid excretion by female guinea pigs. Purified diets containing casein (control, ascorbic-acid-deficient, and casein diets), soy protein or gelatin were fed ad libitum. All except the control contained 50 ppm DDT plus 50 ppm Lindane. (From Chadwick ct a/." By permission of Toricology and Applied Pharmacology.)
Annals New York Academy of Sciences
136
@
2U
INDUCED METABOUC ALTERATIONS
CONTROL CASEIN
400-
ASCORBIC ACID DEFICIENT SOY PROTEIN
300-
GELATIN
>
9
HEPATIC GLYCOGEN
A
LIVER WEIGHT
WEIGHV GAIN
2oo-
FEED CONSUMPTION
i=
U
d loo=
CYTOCHUOME
I
.
6
P-A50
OXIDATIVE HYDROLYSIS
o.DEMmnwE
GLUCURONYL IRANSFERASE
FIGURE4. Effect of pesticide administration and dietary deficiency on enzyme activity, cytochrome P-450, hepatic glycogen content, feed consumption, weight gain and liver weight. For each parameter the mean value of the control animals is represented as 1002SE. The mean values of the other treatment groups relative to that of the controls are plotted as percent2SE [(treatment mean/control mean) xlOO]. Each bar represents the mean value of 4 guinea pigs. (From Chadwick ct a[." By permission of Toxicology and Applied Pharmacology.)
STORAGE AND Treatment Vit. C (ppm)
DDT (mg)
0.0 0.0 3000 3000
0.0 5.0 0.0
5.0
TABLE1 EXCRETION OF "C-y-HCH Excreted 14C.I.
Urine 2.72-tO.56 1.6020.38 2.50f0.74 1.71-10.26
BY
SQUIRREL MONKEY *
-___
Stored yHCH
$ ~
Feces
Liver
Fat
Brain
29.2f3.7 38.9-15.4 28.3243 36.022.0
3.72st1.07 2.2620.49 3.6520.57 2.4350.74
26.5-13.1 18.9k3.9 23.922.4 16.2k3.0
6.221.0 5.Of1.0 6.120.7 4.720.8
* Female squirrel monkeys previously depleted in ascorbic acid were administered 5 mg of y-HCH containing 4.6 pCi. "C-yHCH on day 14 of the indicated treatment schedule and excreta collected for 24 hours prior to sacrifice and tissue analysis. DDT effects were significant (p < 0.10) but vitamin C effects were not. Data from Chadwick et al?' t Avg d p m x 10-%SE of the mean. $ Avg ppm yHCH based on radioactivity present.
Street & Chadwick: Pesticides and Vitamin C
137
be sensitive to the ascorbate status. Impaired enzyme induction is apparent quite early during ascorbic acid depletion i n guinea pigs in which the insecticide Dieldrin ( 2 5 ppm in the diet) was employed to induce 0-demethylation and aniline hydroxylation reactions.’:{ The induced enzyme responses were impaired as early as the third day on the vitamin-C-depletion diet. (Impaired induction was defined as the percentage decline in induced ‘enzymatic activity measured in animals on the ascorbic-acid-deficient diet compared to those receiving 2000 ppm vitamin C with the inducer.) Impairment increased during ascorbic acid depletion roughly corresponding to the fall in ascorbic acid con-
FIGURE 5 . Effect of pesticide administration and ascorbic acid deficiency on the total urinary excretion of Lindanc and Lindane-derived chlorophenols on day I5 (as percent of total consumed Lindanel24-hr urine sample). The excreted Lindane and its metabolites are each represented as a rectangular section of the bar. Each section represents the mean of 4 animals, while the horizontal line in each section represents the SE. (From Chadwick et ul.” By permission of Toxicology and Applied Phurr?rucology.)
centration in liver. (FIGURE 7 ) After about the 12th day of depletion the guinea pigs began to lose body weight at which time basal (non-induced) enzyme activities declined rapidly. Consequently, after the 12th day, “impaired induction” became moot. Indeed, the proportional increase in enzyme activity obtained with the inducer, when compared t o the basal level in scorbutic pigs, can turn out to be equal to or greater than that measured in animals with normal vitamin C status.> While this has been interpreted t o indicate unimpaired microsomal cytochrome synthesis, there is no question but that the scorbutic guinea pig is far less capable of adapting to the presence of inducing
P-450
T
120 RfOUCTlSt
PRO T f l M
MlCROSOMll
0- DtMtTnVLlSE
WE I C U T
lflllllli
~~~
YlllMlM C
v IT A M Iw c
~~
DOT
CLU c uRONV 1 TRdNSffRASt
FIGURE 6. Effect of DDT and ascorbic acid on enzyme activity, cytochrome P-450 content, hepatic microsomal protein content, and liver weight. For each parameter the mean value of the monkeys receiving neither DDT or ascorbic acid is represented as 100% f S E . The mean values of the other treatment groups relative to that of these ascorbic-acid-deficient controls are plotted as percentages (Treatment rnean/control mean x 100). Each bar represents the mean value of 6 monkeys. (From Chadwick er ul.'' By permission of Toxicology and Applied Pharnzacology. )
CVTOCWROMf
0 XlDlTlVt
co
w
Strcet & Chadwick: Pesticides and Vitamin C ASCORBIC ACID IN LIVER (ug/gm)
1 MPAlR MENT 0%
139
25% 5Mc 7 5 %
FIGURE 7. Impairment of induction prior to frank scurvy. Progressive impairment of Dieldrin-induced 0-dernethylation and ascorbic acid concentrations in liver of guinea pigs receiving commercial laboratory diet devoid of ascorbic acid. (From Wagstaff and Street.’:’ By permission of Towicology ond Applied Pharniacology.)
CONTROL
............. ..... ......... .........
DIELDRIN
....... ........ ::.‘.‘.’ .........
AA. DEFICIENT PLUS DIELDRIN. A A M F I C I E I I T PLUS DOT. AADEFICIENT PLUS LIWMWE.
H
H
*?;$
Organochlorine pesticides, typified by DDT, Dieldrin, Lindane and some other well known insecticides, are normally in vivo substrates of drug metabolising enzymes including the monooxygenase and conjugating systems. Their metabolism, and hence toxicity, is subject to many factors known to influence these enzymes, including the animal’s nutritional state. The ascorbic acid status is one well established factor in that respect.l 3 Some organochlorine pesticides, including those already named, are potent “inducers” of the hepatic microsomal drug metabolising Such “induction” is recognized as an important adaptive process in animals and markedly influences the toxic expression of the inducing agent. Stimulation of the glucuronic pathway resulting in enhanced ascorbic acid biosynthesis has been known for many years and utilized as an index of inducer activity.”, 7 In early study of metabolic interaction among organochlorine pesticides we began to monitor ascorbic acid excretion in urine of the rats used in those studies since the interaction was believed to result from hepatic microsomal enzyme induction. Certain organochlorine pesticides such as DDT (FIGURE 1) were found to greatly stimulate ascorbic acid output soon after administration. With continued DDT administration the animals maintained twofold or greater ascorbic acid excretion for nearly six weeksx In contrast the insecticide methoxychlor, a very poor inducer, did not affect ascorbic acid excretion although administered at a level 10 times greater than DDT. These data were interpreted as indicating induction of microsomal enzyme activities by DDT as aminopyrine and heptabarbital, well known inducing agents, produced similar effects. Stimulation of the glucuronic acid pathway by organochlorine inducing agents is also indicated by enhanced excretion of glucuronic acid (FIGURE 2). Both DDT and Lindane (7-HCH) stimulated glucuronic acid excretion by rats but Lindane was considerably more potent.!’ That difference probably results from the fact that Lindane is metabolized to a number of chlorinated phenols which are excreted as glucuronides. The analyses represented in FIGURE 2 are for total glucuronic acid in urine, thus including glucuronide conjugates. These insecticides were also shown to produce similar effects upon glucuronic acid excretion by the squirrel monkey.’”
* The research was aided by USDA regional research funds, USPHS research and training grants ES-00255and GM-1179, and the Utah Community Studies Pesticide Project under contract with the Environmental Protection Agency. 132
Street & Chadwick: Pesticides and Vitamin C
133
Guinea pigs treated similarly with DDT or Lindane also displayed enhanced activity of the glucuronic acid pathway, evident as enhanced glucaric acid excretion (FIGURE 3).11 The data in FIGURE 3 represent groups of female guinea pigs treated in each case but the control with 50 pprn DDT plus 50 ppm Lindane. Enhanced glucaric acid excretion was obtained when the insecticides were administered in a diet containing soy protein or casein, but soy protein supported a much greater response. Gelatin, a poor quality protein, did not support statistically significant increases in glucaric acid excretion. These data,
FIGURL 1. Urinary ascorbic acid excretion by rats administered drugs and organochlorine insecticides in the diet. Commercial laboratory diets containing 50 ppm DDT, 500 pprn methoxychlor, 2000 ppm aminopyrine, 2000 ppm heptabarbital, and 5000 ppm tolbutamide, respectively, were fed to groups of female rats for 8 weeks. Diet intakes were not equalized, however, the ad libitum intakes were not statistically different among groups. Data from Chadwick.*
therefore, whilc confirming that DDT and Lindane stimulate the glucuronic acid pathway, also suggest that protein quality factors influence the enzyme responses obtained. Soy protein in this study gave results, relative to casein, similar to those obtained with female rats in induction experiments.'* A relatively lower response of induced animals upon the casein diet deficient in ascorbic acid was noted in comparison to the normal casein diet. That difference indicates a dependency upon ascorbic acid for the enzyme induction response to develop in the presence of organochlorine pesticide. The data in Frcum 4 support the
Annals New York Academy of Sciences
134
A V E R A P E h I O U N l S (in mg) O F P L U C U R O I I C A C I D E X C A C l E D P E R 24 HOURS VS T I M E ( i n d r y s ) . u
FIGURE 2. Effect of DDT, Lindane and their combination administered i.p. in peanut oil (2 mg of each) to female rats upon urinary glucuronic acid excretion. Dosing was made on day 0. (From Chadwick ct a/? By permission of Toxicology rind Applied Pharmacology. )
conclusion that the enhanced glucaric acid excretion in this species correctly indicated enhanced microsomal enzyme function. Pesticide administration generally resulted in increased cytochrome P-450,and greater hydrolysis of EPN, 0-demethylation of p-nitroanisole, and glucuronide formation from p-nitrophenol. However, ascorbic-acid-deficient animals displayed lower hepatic microsomal enzyme parameters, in comparison to the ascorbic-acid-normal casein group, in all but glucuronyl transferase activity. The absolute comparative responses were somewhat confounded by variable weight gains resulting from the ascorbic acid or protein deficiencies produced by certain diets. Just as the efficiency of drug metabolism is subject to the ascorbic acid status, there is evidence that pesticide degradation and elimination is also impaired by vitamin C deficiency. Correspondingly greater insecticide residue accumulation in tissues results which would be expected to aggravate the chronic toxic effects of the pesticides. The data in FIGURE5 illustrate this relationship in terms of Lindane (7-HCH) metabolism and excretion. The guinea pigs represented in this figure were being continuously treated with 50 ppm DDT plus 50 ppm Lindane in their diets to obtain microsomal enzyme induction. Between the directly comparable pair of treatments, those animals on an ascorbic-acid-free casein diet excreted less than half the total amount of Lindane metabolites as did those on a casein diet sufficient in ascorbic acid. The tissue
Street & Chadwick: Pesticides and Vitamin C
135
residues of Lindane would be proportionately higher in the vitamin-C-deficient guinea pigs. Poor quality proteins in the guinea pig diet potentiated the excretion of Lindane metabolites, a result of the enhanced hepatic microsomal enzyme activities obtained in those cases. Such effects of ascorbic acid deficiency presumably should occur in the primates, including man. Chadwick et a1.l" carried out one short-term experiment with female squirrel monkeys attempting to show effects of an inducing pesticide (DDT) and ascorbic acid deficiency on microsomal enzyme activities and Lindane metabolism. Their findings failed to show significant effects of vitamin C deficiency, except for impaired induction of 0-demethylation activity (FIGURE 6). However trends toward greater induced enzyme activities with supplemental vitamin C were apparent. Lindane metabolism, and consequently its storage in tissue, were not significantly affected by the ascorbate status in that 1). Since the monkeys wcrc only 15 days into ascorbic acid cxperiment (TABLE depletion when examined, the experimental period may have been insufficient to establish greatly altered conditions. Nevertheless, it might be concluded that the trends observed were sufficient to indicate that the general effects in this species are similar to those observed in the guinea pigs. The capacity of the liver to adapt to the presence of inducing agents such as DDT and Lindane through enhanced microsomal enzymatic levels appears to
2.0
-
2
5
-....... -------
CONTROL
1.6
-
---a-
ASCORBIC AClb DEFICIENT CASEIN SOY PROTEIN
cy \
P
GELATIN
V
4
u
GLUCARIC ACID EXCRETION
1.2
-
a
A
12
TIME (in doyr)
FIGURL 3. Urinary glucaric acid excretion by female guinea pigs. Purified diets containing casein (control, ascorbic-acid-deficient, and casein diets), soy protein or gelatin were fed ad libitum. All except the control contained 50 ppm DDT plus 50 ppm Lindane. (From Chadwick ct a/." By permission of Toricology and Applied Pharmacology.)
Annals New York Academy of Sciences
136
@
2U
INDUCED METABOUC ALTERATIONS
CONTROL CASEIN
400-
ASCORBIC ACID DEFICIENT SOY PROTEIN
300-
GELATIN
>
9
HEPATIC GLYCOGEN
A
LIVER WEIGHT
WEIGHV GAIN
2oo-
FEED CONSUMPTION
i=
U
d loo=
CYTOCHUOME
I
.
6
P-A50
OXIDATIVE HYDROLYSIS
o.DEMmnwE
GLUCURONYL IRANSFERASE
FIGURE4. Effect of pesticide administration and dietary deficiency on enzyme activity, cytochrome P-450, hepatic glycogen content, feed consumption, weight gain and liver weight. For each parameter the mean value of the control animals is represented as 1002SE. The mean values of the other treatment groups relative to that of the controls are plotted as percent2SE [(treatment mean/control mean) xlOO]. Each bar represents the mean value of 4 guinea pigs. (From Chadwick ct a[." By permission of Toxicology and Applied Pharmacology.)
STORAGE AND Treatment Vit. C (ppm)
DDT (mg)
0.0 0.0 3000 3000
0.0 5.0 0.0
5.0
TABLE1 EXCRETION OF "C-y-HCH Excreted 14C.I.
Urine 2.72-tO.56 1.6020.38 2.50f0.74 1.71-10.26
BY
SQUIRREL MONKEY *
-___
Stored yHCH
$ ~
Feces
Liver
Fat
Brain
29.2f3.7 38.9-15.4 28.3243 36.022.0
3.72st1.07 2.2620.49 3.6520.57 2.4350.74
26.5-13.1 18.9k3.9 23.922.4 16.2k3.0
6.221.0 5.Of1.0 6.120.7 4.720.8
* Female squirrel monkeys previously depleted in ascorbic acid were administered 5 mg of y-HCH containing 4.6 pCi. "C-yHCH on day 14 of the indicated treatment schedule and excreta collected for 24 hours prior to sacrifice and tissue analysis. DDT effects were significant (p < 0.10) but vitamin C effects were not. Data from Chadwick et al?' t Avg d p m x 10-%SE of the mean. $ Avg ppm yHCH based on radioactivity present.
Street & Chadwick: Pesticides and Vitamin C
137
be sensitive to the ascorbate status. Impaired enzyme induction is apparent quite early during ascorbic acid depletion i n guinea pigs in which the insecticide Dieldrin ( 2 5 ppm in the diet) was employed to induce 0-demethylation and aniline hydroxylation reactions.’:{ The induced enzyme responses were impaired as early as the third day on the vitamin-C-depletion diet. (Impaired induction was defined as the percentage decline in induced ‘enzymatic activity measured in animals on the ascorbic-acid-deficient diet compared to those receiving 2000 ppm vitamin C with the inducer.) Impairment increased during ascorbic acid depletion roughly corresponding to the fall in ascorbic acid con-
FIGURE 5 . Effect of pesticide administration and ascorbic acid deficiency on the total urinary excretion of Lindanc and Lindane-derived chlorophenols on day I5 (as percent of total consumed Lindanel24-hr urine sample). The excreted Lindane and its metabolites are each represented as a rectangular section of the bar. Each section represents the mean of 4 animals, while the horizontal line in each section represents the SE. (From Chadwick et ul.” By permission of Toxicology and Applied Phurr?rucology.)
centration in liver. (FIGURE 7 ) After about the 12th day of depletion the guinea pigs began to lose body weight at which time basal (non-induced) enzyme activities declined rapidly. Consequently, after the 12th day, “impaired induction” became moot. Indeed, the proportional increase in enzyme activity obtained with the inducer, when compared t o the basal level in scorbutic pigs, can turn out to be equal to or greater than that measured in animals with normal vitamin C status.> While this has been interpreted t o indicate unimpaired microsomal cytochrome synthesis, there is no question but that the scorbutic guinea pig is far less capable of adapting to the presence of inducing
P-450
T
120 RfOUCTlSt
PRO T f l M
MlCROSOMll
0- DtMtTnVLlSE
WE I C U T
lflllllli
~~~
YlllMlM C
v IT A M Iw c
~~
DOT
CLU c uRONV 1 TRdNSffRASt
FIGURE 6. Effect of DDT and ascorbic acid on enzyme activity, cytochrome P-450 content, hepatic microsomal protein content, and liver weight. For each parameter the mean value of the monkeys receiving neither DDT or ascorbic acid is represented as 100% f S E . The mean values of the other treatment groups relative to that of these ascorbic-acid-deficient controls are plotted as percentages (Treatment rnean/control mean x 100). Each bar represents the mean value of 6 monkeys. (From Chadwick er ul.'' By permission of Toxicology and Applied Pharnzacology. )
CVTOCWROMf
0 XlDlTlVt
co
w
Strcet & Chadwick: Pesticides and Vitamin C ASCORBIC ACID IN LIVER (ug/gm)
1 MPAlR MENT 0%
139
25% 5Mc 7 5 %
FIGURE 7. Impairment of induction prior to frank scurvy. Progressive impairment of Dieldrin-induced 0-dernethylation and ascorbic acid concentrations in liver of guinea pigs receiving commercial laboratory diet devoid of ascorbic acid. (From Wagstaff and Street.’:’ By permission of Towicology ond Applied Pharniacology.)
CONTROL
............. ..... ......... .........
DIELDRIN
....... ........ ::.‘.‘.’ .........
AA. DEFICIENT PLUS DIELDRIN. A A M F I C I E I I T PLUS DOT. AADEFICIENT PLUS LIWMWE.
H
H
*?;$
