ENVIRONMENTAL
RESEARCH
Effects Function
20, 148-153 (1979)
of Subacute Feeding of Carbaryl on Mixed Oxidase and on Acute Toxicity of Parathion and Propoxur in Rats NESKO K. NESKOVI~
INEP,
Department
of Pesticides,
Banatska
3lb,
P.O.
Box
46, 11080 Zemun,
Yugoslavia
ReceivedDecember 26, 1978 The effects of carbaryl on NADPH-cytochrome c reductase activity and cytochrome content in liver microsomes and on acute toxicity of parathion and propoxur were examined. Food containing carbaryl (2000 ppm) was provided to rats during a 60 days period. In animals fed diets with carbaryl, no statistically significant difference in body weight was observed when compared with control animals, although an increase in liver weight was established in males. The NADPH-cytochrome c reductase activity was decreased significantly in carbaryl-treated animals. Cytochrome P-450 content was increased in male animals fed diets with carbaryl; the increase was 36%. The intraperitoneal LDS, of parathion and propoxur increased in animals fed diets containing carbaryl. The increase of the parathion LDS, was over 50% in females; while the LD,, for propoxur in males increased 34%, and in females 36% in relation to the values obtained in control animals. P-450
INTRODUCTION
Efforts to increase and improve the production of food and other material goods have resulted in increased application of various compounds for pest control every year. One of the most widely used insecticides, carbaryl, which belongs to the group of carbamate compounds, has been applied intensively for pest control in agricuiture, veterinary medicine, and communal hygiene for a long period of time. Attention is particularly directed to the study of changes occurring in the organism due to prolonged intake (most often by food) of small amounts of these compounds. Cecil et al. (1974) examined the effect of dietary carbaryl (100 ppm during 2 months) on liver weight, lipids, and vitamin A content in rats, while Dikshith et al. (1976) examined histological and biochemical changes in some organs of rats which were treated orally with 200 mg/kg of carbaryl three times weekly for 90 days. Others have examined the effect of longer carbaryl exposure on liver metabolic enzymes and on the toxicity of some other pesticides (Stevens et al., 1972; Cress and Brother, 1974; Gordon et al., 1978). This paper reports the effect of carbaryl exposure on some multifunctional hepatic oxidases and on the acute toxicity of the insecticides parathion and propoxur . MATERIALS
AND METHODS
The following compounds were used in these experiments: carbaryl (1-naphthyl N-methylcarbamate), purity 98%, produced by Zorka, Sabac, Yugoslavia; parathion (U,O-diethyl 0-nitrophenyl phosphorothioate), purity 99.2%; and propoxur 148 0013-9351/79/050148-06$02.00/O Copyright All rights
@ 1979 by Academic Press, Inc. of reproduction in any form reserved.
EFFECTS
OF
CARBARYL
FEEDING
149
IN RATS
(Zisopropoxyphenyl N-methylcarbamate), purity 99.2%, both produced by Bayer AG, Leverkusen, West Germany. Albino rats of each sex, 150- 175 g body wt at the beginning of the experiment were kept in polyethylene cages (three animals in each) at room temperatures of 23-25°C during the entire experiment. All animals consumed food and water ad /i&turn during a 60-day period. Control groups were fed diets for laboratory rats (Veterinary Institute, Zemun), and the experimental animals were fed a diet containing 2000 ppm of carbaryl. After the 60-day period, the animals were sacrificed by decapitation, the liver was removed, transferred immediately to cold 1.15% KC1 solution, and weighed. Microsomes were isolated from the liver of control and experimental animals according to the procedure described by Cinti et al. (1972). Protein determinations were carried out by the method of Lowry et al. (1951) with bovine serum albumin as the standard. Cytochrome P-450 was determined according to the method of Omura and Sato ( 1964). P-450 concentration was calculated from the absorbance difference at 450 and 490 nm after reduction with sodium dithionite and gassing with carbon monoxide, using an extinction coefficient of 91.0 cm-‘nM-‘. The activity of microsomal NADPH-cytochrome c reductase was estimated spectrophotometrically at 550 nm by following cytochrome c reduction as described earlier (NeSkovid et al., 1973). For acute toxicity determination, parathion or propoxur was administered intraperitoneally (ip). The animals were observed for 5 days after the treatment, and the LD,, was determined by the method of Litchfield and Wilcoxon (1949). Statistical analysis of the results was carried out by methods described by Snedecor and Cochran (1967). Differences between the mean values of control and test groups were analyzed using the Student’s t test. The 0.05 level of probability was used as the criterion of significance.
0 m
control carbaryl
male
! female
_L
6 FIG. days).
1. Body
weight
gain (mean
Timetdays) 2 SD of 16 male and 16 female
i IO
1 m animals)
.O during
60 the experiment
(60
150
NESKO K. NESKOVId TABLE THE EFFECT
Sex
Male
Female
OF DIETARY
CARBARYL
ON BODY
1 WEIGHT
AND LIVER
WEIGHT
OF RATS”
Diet
Days
Body weight (g)
Liver weight (9)
Index m
Control Carbaryl
60 60
304 2 8.0 298 + 5.0
6.3 k 0.4 7.2 T 0.9
2.0 k 0.1 2.4 + 0.2
Control Carbaryl
60 60
211 + 4.0 201 + 2.0
5.5 + 0.2 6.0 + 0.3
2.6 + 0.1 3.0 r 0.1
” Mean k SD. There were 16 animals in each group. * Significantly different from control group (P < 0.05).
RESULTS
Figure 1 presents the weight increase in controls and in animals fed diets with carbaryl for 60 days. The weight increase in experimental animals was slightly less than in the controls during the first 10 days. The decreased rate of weight gain in test animals in the first phase of the experiments was probably due to somewhat poorer intake of food containing carbaryl. In later phases of the experiment no differences were observed in food intake between control and test animals. At the end of the 60-day experiment, weight in control and test animals was the same (Table 1). However, a significant increase in liver weight in male animals fed diets with carbaryl was noted. With regard to important multifunctional oxidases which metabolize toxic chemicals, the effects of subacute application of carbaryl on cytochrome P-450 content and NADPH-cytochrome c reductase activity were studied. NADPH-Cytochrome c reductase activity decreased in animals fed diets containing carbaryl (Table 2). In males the decrease was about 15%, and in females 22%, in comparison with the values obtained in control animals. Both values are statistically different from controls. Increases in cytochrome P-450 concentration were also recorded. In males the TABLE
2
THE EFFECT OF DIETARY CARBARYL ON HEPATIC MICROSOMAL NADPH-CYTOCHROME REDUCTASE ACTIVITY AND CYTOCHROME P-450 CONTENT IN RATS”
Sex
NADPH-Cytochrome c reductase*
c
Cytochrome P-450'
Diet
Days
Male
Control Carbaryl
60 60
97.0 2 6.2 81.9 2 4.3”
0.47 + 0.02 0.64 2 0.03"
Female
Control Carbaryl
60 60
80.8 2 5.2 62.8 r 3.7"
0.52 2 0.03 0.57 t 0.03
n Mean ? SD. There were 16 animals in each group. b nmoles cytochrome c reducediminlmg microsomal protein. c nmol/mg microsomal protein. ” Significantly different from control group (P < 0.05).
EFFECTS
THE EFFECT
Sex Male
Female
OF DIETARY
OF
CARBARYL
CARBARYL
FEEDING
TABLE 3 ON ACUTE
IN
151
RATS
TOXICITY OF PARATHION IN RATS Dose @pm)
Diet
Days
Control
60
0
Carbaryl
60
2000
Control
60
0
Carbaryl
60
2000
17.0 (I 1.2-25.8)” 19.5 (15.3-24.8) 7.2 (5.4-9.5) 11.0” (7.6- 15.8)
(’ 95% confidence limits. b Significantly different from control group (P < 0.05). was about 36%, and in females 8.4%, in comparison with control values. Only the increase observed in males is statistically significant. Sixty day exposure to carbaryl induced changes in the acute toxicity of parathion and propoxur insecticides which, like carbaryl, are anticholinesterase agents. Acute ip LDsO of parathion, expressed as milligrams per kilogram body weight, was 19.5 mg/kg in males fed diets containing carbaryl and 17.0 mg/kg for controls. In females, the LD,, value for treated rats was 11.0; for control 7.2 mg/kg (Table 3). Thus, the LDsO value in males fed carbaryl was about 15% higher, and LD,, in females over 50% greater than control values. Only the difference observed in females is statistically significant. The LDSo values for propoxur in rats fed carbaryl were also higher in relation to the control values (Table 4). The increase in males was 34%, and in females about 36%, in relation to LDso values obtained in control animals. Both differences are statistically significant. Both compounds were more toxic in female than in male rats. increase
TABLE
4
THE EFFIXT OF DIETARY CARBARYL ON ACUTE TOXICITY OF PROPOXUR IN RATS Sex Male
Female
Dose (rvm)
Diet
Days
Control
60
0
Carbaryl
60
2000
Control
60
0
Carbaryl
60
2000
’ 95% confidence limits. ’ Signiticantly different from control (P < 0.05)
LR,, (m&z) 44.0 (30.3-63.8)’ 59.0” (49.9-84.9) 33.0 (23.2-46.9) 45 .O” (34.3-58.9)
152
NESKO K. NESKOVIC
DISCUSSION
Due to constant and sometimes uncontrolled application, some pesticides are increasingly present pollutants of our air, water, and food products (Tiel, 1972) and result in various biological changes. Carbamate insecticides, if taken for a long period of time, can alter the toxic effects of other pesticides (Dikshith et al., 1976; Puiynska, 1977; Gordon et al., 1978).
The results described show that carbaryl exposure with food (2000 ppm during 60 days) does not affect body weight increases in rats, but does induce an increase in liver weight in males. Similar results were observed by Cecil et al. (1974) in rats fed diets with 100 ppm carbaryl during a 2-month period. In animals of both sexes the carbaryl-containing diet significantly reduced NADPH-cytochrome c reductase activity. Cytochrome P-450 content was significantly higher in male animals fed carbaryl-containing diets. Cress and Strother (1974) have demonstrated an increase of cytochrome P-450 in mice fed diets containing 25 mmole/kg carbaryl (about 5000 ppm) during a 1Cday period. In contrast to our results, they reported a decrease in body weight as well as in liver weight in test animals. They also established that the ‘consumption of food containing carbaryl was less than for the control diet which most likely accounted for the decrease of body weight in test animals. This was not the case in the experiments reported here; no differences in body weight between control and test animals were demonstrated. Stevens et al. (1972) have found that daily application for 3 -5 days of one-half the LDsO for carbaryl (336.7 pmole/kg) increased hexobarbital oxidation and aniline metabolism. Increased activity of metabolic enzymes can influence the toxicity of some xenobiotics. Our results show that the acute toxicity of propoxur decreased in both sexes and parathion toxicity decreased in females which were fed diets with carbaryl for 60 days. Our results agree with those of Cress and Strother (1974), and with Gordon et al. (1978), showing that some carbamate compounds can reduce toxic effect of the organophosphates somane, sarine, tabune, and VX. It is probable in this case, as in the experiments with carbaryl, that more intensive degradation of the compounds to nontoxic or less toxic products due to increased activity of metabolic enzymes in liver accounts for the lower toxicity of parathion and propoxur observed in animals fed diets containing carbaryl. ACKNOWLEDGMENT The author gratefully acknowledges the excellent technical assistance of Mrs. Zora Radenovic-Zagar.
REFERENCES Cecil, H. C., Harris, S. J., and Bitman, J. (1974). Effects of nonpersistent pesticides on liver weight, lipids and vitamin A of rats and quail. Bull. Environ. Contam. Toxicol. 11, 4%-499. Cinti, D. L., Moldeus, P., and Schenkman, J. B. (1972). Kinetic parameters of drug-metabolizing enzymes in Caz+-sedimented microsomes from rat liver. Biochem. Pharmacol. 21, 3249-3256. Cress, R. C., and Strother, A. (1974). Effects on drug metabolism of carbaryl and I-paphthol in the mouse. Life Sci. 14, 861-872. Dikshith, T. S. S., Gupta, P. K., Gour, J. C., Datta, K. K., and Mathur, A. K. (1976). Ninety day toxicity of carbaryl in male rats. Environ. Res. 12, 161- 170.
EFFECTS
OF CARBARYL
FEEDING
IN RATS
153
Gordon, J. J., Leadbeater, L., and Maidment, M. P. (1978). The protection of animals against organophosphate poisoning by pretreatment with a carbamate. Toric,ol. App/. Pharmad. 43, 207-216. Litchtield, J. T., and Wilcoxon, F. (1949). A simplified method of evaluating dose-effect experiments. J. Pharmacol. Exp. Thrr. 96, 99- 113. Lowry, 0. H., Rosebrough, N. J., Farr, A. L., and Randall, P. J. ( 195 1). Protein measurement with the folin-protein reagent. J. Bid. Chem. 193, 265-275. NeSkoviC, N., Vitorovic, S., and Plesnicar, M. (1973). The role of liver microsomal enzymes in the metabolism of parathion. Eiorhrm. Pharmud. 22, 2943-2946. Omura, T., and Sato, R. (1964). The carbon monoxide-binding pigment of liver microsomes. I. Evidence for its hemoprotein nature. J. Bid. Chrm. 239, 2370-2378. Puiynska, L. (1977). The effect of propoxur on rats fed diets differing in protein content. Er~tiron. Rec. 14. 152- 163. Snedecor, G. W., and Cochran, W. G. (1967). “Statistical Methods.” 6th ed. Iowa State Univ. Press. Ames. Stevens, J. T., Stitzel. R. E., and McPhillips, J. J. (1972). The effects of subacute administration of anticholinesterase insecticides on hepatic microsomal metabolism. Life Sci. 11, 423-431. Tiel, N. V. (1972). Pesticides in environment and food. In “Environmental Quality and Safety“ (F. Coulston and F. Korte, Eds.). Vol. 1, pp. 180- 189. Academic Press. New York.
RESEARCH
Effects Function
20, 148-153 (1979)
of Subacute Feeding of Carbaryl on Mixed Oxidase and on Acute Toxicity of Parathion and Propoxur in Rats NESKO K. NESKOVI~
INEP,
Department
of Pesticides,
Banatska
3lb,
P.O.
Box
46, 11080 Zemun,
Yugoslavia
ReceivedDecember 26, 1978 The effects of carbaryl on NADPH-cytochrome c reductase activity and cytochrome content in liver microsomes and on acute toxicity of parathion and propoxur were examined. Food containing carbaryl (2000 ppm) was provided to rats during a 60 days period. In animals fed diets with carbaryl, no statistically significant difference in body weight was observed when compared with control animals, although an increase in liver weight was established in males. The NADPH-cytochrome c reductase activity was decreased significantly in carbaryl-treated animals. Cytochrome P-450 content was increased in male animals fed diets with carbaryl; the increase was 36%. The intraperitoneal LDS, of parathion and propoxur increased in animals fed diets containing carbaryl. The increase of the parathion LDS, was over 50% in females; while the LD,, for propoxur in males increased 34%, and in females 36% in relation to the values obtained in control animals. P-450
INTRODUCTION
Efforts to increase and improve the production of food and other material goods have resulted in increased application of various compounds for pest control every year. One of the most widely used insecticides, carbaryl, which belongs to the group of carbamate compounds, has been applied intensively for pest control in agricuiture, veterinary medicine, and communal hygiene for a long period of time. Attention is particularly directed to the study of changes occurring in the organism due to prolonged intake (most often by food) of small amounts of these compounds. Cecil et al. (1974) examined the effect of dietary carbaryl (100 ppm during 2 months) on liver weight, lipids, and vitamin A content in rats, while Dikshith et al. (1976) examined histological and biochemical changes in some organs of rats which were treated orally with 200 mg/kg of carbaryl three times weekly for 90 days. Others have examined the effect of longer carbaryl exposure on liver metabolic enzymes and on the toxicity of some other pesticides (Stevens et al., 1972; Cress and Brother, 1974; Gordon et al., 1978). This paper reports the effect of carbaryl exposure on some multifunctional hepatic oxidases and on the acute toxicity of the insecticides parathion and propoxur . MATERIALS
AND METHODS
The following compounds were used in these experiments: carbaryl (1-naphthyl N-methylcarbamate), purity 98%, produced by Zorka, Sabac, Yugoslavia; parathion (U,O-diethyl 0-nitrophenyl phosphorothioate), purity 99.2%; and propoxur 148 0013-9351/79/050148-06$02.00/O Copyright All rights
@ 1979 by Academic Press, Inc. of reproduction in any form reserved.
EFFECTS
OF
CARBARYL
FEEDING
149
IN RATS
(Zisopropoxyphenyl N-methylcarbamate), purity 99.2%, both produced by Bayer AG, Leverkusen, West Germany. Albino rats of each sex, 150- 175 g body wt at the beginning of the experiment were kept in polyethylene cages (three animals in each) at room temperatures of 23-25°C during the entire experiment. All animals consumed food and water ad /i&turn during a 60-day period. Control groups were fed diets for laboratory rats (Veterinary Institute, Zemun), and the experimental animals were fed a diet containing 2000 ppm of carbaryl. After the 60-day period, the animals were sacrificed by decapitation, the liver was removed, transferred immediately to cold 1.15% KC1 solution, and weighed. Microsomes were isolated from the liver of control and experimental animals according to the procedure described by Cinti et al. (1972). Protein determinations were carried out by the method of Lowry et al. (1951) with bovine serum albumin as the standard. Cytochrome P-450 was determined according to the method of Omura and Sato ( 1964). P-450 concentration was calculated from the absorbance difference at 450 and 490 nm after reduction with sodium dithionite and gassing with carbon monoxide, using an extinction coefficient of 91.0 cm-‘nM-‘. The activity of microsomal NADPH-cytochrome c reductase was estimated spectrophotometrically at 550 nm by following cytochrome c reduction as described earlier (NeSkovid et al., 1973). For acute toxicity determination, parathion or propoxur was administered intraperitoneally (ip). The animals were observed for 5 days after the treatment, and the LD,, was determined by the method of Litchfield and Wilcoxon (1949). Statistical analysis of the results was carried out by methods described by Snedecor and Cochran (1967). Differences between the mean values of control and test groups were analyzed using the Student’s t test. The 0.05 level of probability was used as the criterion of significance.
0 m
control carbaryl
male
! female
_L
6 FIG. days).
1. Body
weight
gain (mean
Timetdays) 2 SD of 16 male and 16 female
i IO
1 m animals)
.O during
60 the experiment
(60
150
NESKO K. NESKOVId TABLE THE EFFECT
Sex
Male
Female
OF DIETARY
CARBARYL
ON BODY
1 WEIGHT
AND LIVER
WEIGHT
OF RATS”
Diet
Days
Body weight (g)
Liver weight (9)
Index m
Control Carbaryl
60 60
304 2 8.0 298 + 5.0
6.3 k 0.4 7.2 T 0.9
2.0 k 0.1 2.4 + 0.2
Control Carbaryl
60 60
211 + 4.0 201 + 2.0
5.5 + 0.2 6.0 + 0.3
2.6 + 0.1 3.0 r 0.1
” Mean k SD. There were 16 animals in each group. * Significantly different from control group (P < 0.05).
RESULTS
Figure 1 presents the weight increase in controls and in animals fed diets with carbaryl for 60 days. The weight increase in experimental animals was slightly less than in the controls during the first 10 days. The decreased rate of weight gain in test animals in the first phase of the experiments was probably due to somewhat poorer intake of food containing carbaryl. In later phases of the experiment no differences were observed in food intake between control and test animals. At the end of the 60-day experiment, weight in control and test animals was the same (Table 1). However, a significant increase in liver weight in male animals fed diets with carbaryl was noted. With regard to important multifunctional oxidases which metabolize toxic chemicals, the effects of subacute application of carbaryl on cytochrome P-450 content and NADPH-cytochrome c reductase activity were studied. NADPH-Cytochrome c reductase activity decreased in animals fed diets containing carbaryl (Table 2). In males the decrease was about 15%, and in females 22%, in comparison with the values obtained in control animals. Both values are statistically different from controls. Increases in cytochrome P-450 concentration were also recorded. In males the TABLE
2
THE EFFECT OF DIETARY CARBARYL ON HEPATIC MICROSOMAL NADPH-CYTOCHROME REDUCTASE ACTIVITY AND CYTOCHROME P-450 CONTENT IN RATS”
Sex
NADPH-Cytochrome c reductase*
c
Cytochrome P-450'
Diet
Days
Male
Control Carbaryl
60 60
97.0 2 6.2 81.9 2 4.3”
0.47 + 0.02 0.64 2 0.03"
Female
Control Carbaryl
60 60
80.8 2 5.2 62.8 r 3.7"
0.52 2 0.03 0.57 t 0.03
n Mean ? SD. There were 16 animals in each group. b nmoles cytochrome c reducediminlmg microsomal protein. c nmol/mg microsomal protein. ” Significantly different from control group (P < 0.05).
EFFECTS
THE EFFECT
Sex Male
Female
OF DIETARY
OF
CARBARYL
CARBARYL
FEEDING
TABLE 3 ON ACUTE
IN
151
RATS
TOXICITY OF PARATHION IN RATS Dose @pm)
Diet
Days
Control
60
0
Carbaryl
60
2000
Control
60
0
Carbaryl
60
2000
17.0 (I 1.2-25.8)” 19.5 (15.3-24.8) 7.2 (5.4-9.5) 11.0” (7.6- 15.8)
(’ 95% confidence limits. b Significantly different from control group (P < 0.05). was about 36%, and in females 8.4%, in comparison with control values. Only the increase observed in males is statistically significant. Sixty day exposure to carbaryl induced changes in the acute toxicity of parathion and propoxur insecticides which, like carbaryl, are anticholinesterase agents. Acute ip LDsO of parathion, expressed as milligrams per kilogram body weight, was 19.5 mg/kg in males fed diets containing carbaryl and 17.0 mg/kg for controls. In females, the LD,, value for treated rats was 11.0; for control 7.2 mg/kg (Table 3). Thus, the LDsO value in males fed carbaryl was about 15% higher, and LD,, in females over 50% greater than control values. Only the difference observed in females is statistically significant. The LDSo values for propoxur in rats fed carbaryl were also higher in relation to the control values (Table 4). The increase in males was 34%, and in females about 36%, in relation to LDso values obtained in control animals. Both differences are statistically significant. Both compounds were more toxic in female than in male rats. increase
TABLE
4
THE EFFIXT OF DIETARY CARBARYL ON ACUTE TOXICITY OF PROPOXUR IN RATS Sex Male
Female
Dose (rvm)
Diet
Days
Control
60
0
Carbaryl
60
2000
Control
60
0
Carbaryl
60
2000
’ 95% confidence limits. ’ Signiticantly different from control (P < 0.05)
LR,, (m&z) 44.0 (30.3-63.8)’ 59.0” (49.9-84.9) 33.0 (23.2-46.9) 45 .O” (34.3-58.9)
152
NESKO K. NESKOVIC
DISCUSSION
Due to constant and sometimes uncontrolled application, some pesticides are increasingly present pollutants of our air, water, and food products (Tiel, 1972) and result in various biological changes. Carbamate insecticides, if taken for a long period of time, can alter the toxic effects of other pesticides (Dikshith et al., 1976; Puiynska, 1977; Gordon et al., 1978).
The results described show that carbaryl exposure with food (2000 ppm during 60 days) does not affect body weight increases in rats, but does induce an increase in liver weight in males. Similar results were observed by Cecil et al. (1974) in rats fed diets with 100 ppm carbaryl during a 2-month period. In animals of both sexes the carbaryl-containing diet significantly reduced NADPH-cytochrome c reductase activity. Cytochrome P-450 content was significantly higher in male animals fed carbaryl-containing diets. Cress and Strother (1974) have demonstrated an increase of cytochrome P-450 in mice fed diets containing 25 mmole/kg carbaryl (about 5000 ppm) during a 1Cday period. In contrast to our results, they reported a decrease in body weight as well as in liver weight in test animals. They also established that the ‘consumption of food containing carbaryl was less than for the control diet which most likely accounted for the decrease of body weight in test animals. This was not the case in the experiments reported here; no differences in body weight between control and test animals were demonstrated. Stevens et al. (1972) have found that daily application for 3 -5 days of one-half the LDsO for carbaryl (336.7 pmole/kg) increased hexobarbital oxidation and aniline metabolism. Increased activity of metabolic enzymes can influence the toxicity of some xenobiotics. Our results show that the acute toxicity of propoxur decreased in both sexes and parathion toxicity decreased in females which were fed diets with carbaryl for 60 days. Our results agree with those of Cress and Strother (1974), and with Gordon et al. (1978), showing that some carbamate compounds can reduce toxic effect of the organophosphates somane, sarine, tabune, and VX. It is probable in this case, as in the experiments with carbaryl, that more intensive degradation of the compounds to nontoxic or less toxic products due to increased activity of metabolic enzymes in liver accounts for the lower toxicity of parathion and propoxur observed in animals fed diets containing carbaryl. ACKNOWLEDGMENT The author gratefully acknowledges the excellent technical assistance of Mrs. Zora Radenovic-Zagar.
REFERENCES Cecil, H. C., Harris, S. J., and Bitman, J. (1974). Effects of nonpersistent pesticides on liver weight, lipids and vitamin A of rats and quail. Bull. Environ. Contam. Toxicol. 11, 4%-499. Cinti, D. L., Moldeus, P., and Schenkman, J. B. (1972). Kinetic parameters of drug-metabolizing enzymes in Caz+-sedimented microsomes from rat liver. Biochem. Pharmacol. 21, 3249-3256. Cress, R. C., and Strother, A. (1974). Effects on drug metabolism of carbaryl and I-paphthol in the mouse. Life Sci. 14, 861-872. Dikshith, T. S. S., Gupta, P. K., Gour, J. C., Datta, K. K., and Mathur, A. K. (1976). Ninety day toxicity of carbaryl in male rats. Environ. Res. 12, 161- 170.
EFFECTS
OF CARBARYL
FEEDING
IN RATS
153
Gordon, J. J., Leadbeater, L., and Maidment, M. P. (1978). The protection of animals against organophosphate poisoning by pretreatment with a carbamate. Toric,ol. App/. Pharmad. 43, 207-216. Litchtield, J. T., and Wilcoxon, F. (1949). A simplified method of evaluating dose-effect experiments. J. Pharmacol. Exp. Thrr. 96, 99- 113. Lowry, 0. H., Rosebrough, N. J., Farr, A. L., and Randall, P. J. ( 195 1). Protein measurement with the folin-protein reagent. J. Bid. Chem. 193, 265-275. NeSkoviC, N., Vitorovic, S., and Plesnicar, M. (1973). The role of liver microsomal enzymes in the metabolism of parathion. Eiorhrm. Pharmud. 22, 2943-2946. Omura, T., and Sato, R. (1964). The carbon monoxide-binding pigment of liver microsomes. I. Evidence for its hemoprotein nature. J. Bid. Chrm. 239, 2370-2378. Puiynska, L. (1977). The effect of propoxur on rats fed diets differing in protein content. Er~tiron. Rec. 14. 152- 163. Snedecor, G. W., and Cochran, W. G. (1967). “Statistical Methods.” 6th ed. Iowa State Univ. Press. Ames. Stevens, J. T., Stitzel. R. E., and McPhillips, J. J. (1972). The effects of subacute administration of anticholinesterase insecticides on hepatic microsomal metabolism. Life Sci. 11, 423-431. Tiel, N. V. (1972). Pesticides in environment and food. In “Environmental Quality and Safety“ (F. Coulston and F. Korte, Eds.). Vol. 1, pp. 180- 189. Academic Press. New York.
