ENVIRONMENTAL RESEARCH 55, 129--134 (1991)
Effects of Pyrethroid Insecticides on Hepatic Microsomal Enzymes in Rats JERZY KRECHNIAK AND KRYSTYNA WRZEgNIOWSKA
Medical Academy, Department of Toxicology, AI. Hallera 107, 80-416 Gdahsk-Wrzeszcz, Poland Received October 31, 1990 The effects of pyrethroid insecticides on hepatic microsomal enzymes were studied in rats. Animals were treated orally with cypermethrin (80 mg/kg), deltamethrin (15 mg/kg), and permethrin (I00 mg/kg), as a solution in soyabean oil, for 1 to 20 days. The content of cytochromes P-450 and bs, activity of NADPH cytochrome P-450 reductase, glutathione S-transferase, aniline 4-hydroxylase, p-nitroanisote O-demethylase in microsomes, the activity of glutathione S-transferase, and the level of sulfhydryl groups in cytosol were determined. Also the relative liver weight was measured. Only few changes in the investigated parameters were ascertained. These changes have an irregular and transient character. On the whole, the action of pyrethroids on microsomal enzymes results in a slight induction. © 1991AcademicPress,Inc.
INTRODUCTION
A number of pesticides cause various changes in hepatic microsomal enzyme activity. Organophosphate insecticides are generally numbered among moderate inhibitors of microsomal enzyme systems. Prominent among the compounds with microsomal enzymes inducing activity are the chlorinated hydrocarbon insecticides. Experiments performed on pyrethroid insecticides gave different results. Some authors showed that synthetic pyrethroids did not markedly influence the microsomal liver enzymes (Riviere et at., 1983; Habazin-Novak et al., 1985; Febacher et al., 1980); others found an increase (Habazin-Novak and Plestina, 1984; Kagan et al., 1986; Anadon et al., 1988) or decrease (Tang et al., 1987) of their activity. The obtained disparities may result from different methods of pyrethroids administration, various species used in the experiments, as well as different parameters determined. The aim of this study was to investigate the effects of the commonly used pyrethroid insecticides: cypermethrin, deltamethrin, and permethrin on the hepatic microsomal enzymes in rats. MATERIALS AND METHODS Chemicals. The following pyrethroid insecticides were used in this study: cypermethrin--95% purity, obtained from Shell Research Ltd. (Sittingbourne, England); deltamethrin--98% purity, produced by Roussel-Uclaf Romainville, France; permethrin--96% purity, obtained from Wellcome International Trading Ltd. (Berkhamstad Herts, England). A n i m a l s a n d administration. Male albino rats weighing 200 +- 20 g were given daily the following doses of pyrethroids: cypermethrin 80 mg/kg, deltamethrin 15 129 0013-9351/91 $3.00 Copyright© 1991by AcademicPress, Inc. All rightsof reproductionin any formreserved.
130
KRECHNIAK AND WRZEgNIOWSKA
mg/kg, and permethrin 100 mg/kg. The pyrethroids were administered orally as solutions in soyabean oil. Control animals received a corresponding amount of the solvent. Three experiments were performed. In the first one, cypermethrin, deltamethrin, and permethrin were administered up to 4 days; in the second, cypermethrin and deltamethrin were given up to 20 days; in the third, cypermethrin and permethrin were given up to 20 days. M e t h o d s . The day after the administration of the last dose the animals were killed by cervical dislocation. Liver was immediately isolated and the whole tissue homogenized in ice-cooled isotonic potasium chloride---0.01 M phosphate buffer (pH 7.4) was prepared. To obtain the postmitochondrial supernatant, the liver homogenate was centrifuged at 15.000 g for 30 min. The resultant supernatant was centrifuged at 100.000 g for 1 hr in a refrigerated ultracentrifuge to isolate the microsomal fraction. In the postmitochondrial supernatant the activity of 4-nitroanisole O-demethylase (Netter and Seidel, 1964) and aniline 4-hydroxylase (Kato and Gillette, 1965) were determined. In the microsomal fraction the content of cytochromes P-450 and b 5 (Omura and Sato, 1964) and the activity of NADH cytochrome P-450 reductase (Masters et al., 1967) were assessed. The activity of glutathione S-transferase (Habig et al., 1974) was determined in the microsomal and cytosolic fraction. The level of sulfhydryl groups (Ellman, 1959) was assessed in the cytosolic fraction. Protein in the isolated subcellular fractions was determined by the method of Lowry et al. (1951). Statistical analysis was performed using Student's t-test. RESULTS The effects of cypermethrin, deltamethrin, and permethrin given for 1, 2, and 4 days on relative liver weights, the content of cytochromes P-450 and bs, the activity of glutathione S-transferase, and the level of sulfhydryl groups are presented in Table 1. In this experiment only a significant decrease in liver body weight ratio in animals treated with deltamethrin was ascertained. No distinctive influence of the administered pyrethroids on the activity of the investigated enzymes was established. The effects of cypermethrin and deltamethrin administered for 10 and 20 days on relative liver weights, the content of cytochromes P-450 and b5 and the activity of microsomal and cytosolic glutathione S-transferase are presented in Table 2. Statistically significant differences were found only after the administration of pesticides for 20 days. Cypermethrin brought about an increase in the content of cytochrome P-450, deltamethrin in cytochrome bs. Both pyrethroids caused a distinctive decrease in the activity of cytosolic glutathione S-transferase. The effects of cypermethrin and permethrin, given for 6, 10, and 20 days, on the activity of 4-nitroanisole O-demethylase, aniline 4-hydroxylase, and NADPH cytochrome P-450 reductase are presented in Table 3. Permethrin after 10 days of dosing caused a significant increase in the activity of cytochrome P-450 reductase, and after 20 days an increase in the activity of
131
EFFECTS OF PYRETHROID INSECTICIDES
.,-,
o
z
:=1.
exO ~
,0
E~
Z
~E
~
+1
+1
¢-1
132
KRECHNIAK AND WRZEgNIOWSKA
TABLE 2 LIVER WEIGHT AND ACTIVITY OF ENZYMES IN RATS GIVEN CYPERMETHRIN AND DELTAMETHRIN
Cytochrome Days of
dosing 10 20
Glutathione S-transferase (nmole/min/g protein)
Cytochrome
Liver weight (% body weight)
P-450
b5
(nmole/gprotein)
(nmole/gprotein)
O
O
O
C
D
C
D
C
Cytosol
D
O
Microsomes
C
D
O
C
D
-SD
3.3 3.7 3.8 0.47 0 . 5 0 0.54 0 . 4 3 0 . 3 5 0.11 0.08
0 . 3 4 0 . 2 0 0 . 2 6 0 . 1 8 78.3 6 5 . 6 0.11 0 . 0 4 0.11 0 . 0 6 23.9 16.4
7 0 . 3 3.30 3.35 3.02 10.8 1.26 1.73 1.33
-SD
3.4 3.3 3.8 0.46 0.62x 0.45 0 . 4 8 0.43 0 . 0 4 0 . 1 0
0 . 5 4 0 . 3 4 0.31 0.52x 76.5 49.6xx 53.7x 3.40 2.99 3.35 0 . 1 0 0.11 0.11 0 . 1 2 14.3 14.5 10.1 1.38 1.48 1.83
Note. Values are mean ~ -+ S.D. (n = 6). x, Significantly different from controls (P < 0.05); xx, significantly different from controls (P < 0.005); C, animals treated with 80 mg/kg of cypermethrin; D, animals treated with 15 mg/kg of deltamethrin; O, control animals treated with soyabean oil.
aniline 4-hydroxylase. No significant changes in the activity of the investigated enzymes were found in animals treated with cypermethrin. DISCUSSION
The effects of different pyrethroid insecticides on hepatic microsomal enzyme activity have been examined by several authors. Riviere et al. (1983) found that permethrin, cypermethrin, deltamethrin, and fenvalerate gave no or only a moderate increase in hepatic microsomal cytochrome P-450 level and NADPH cytochrome P-450 reductase activities in the Japanese quail. A significant increase in hepatic microsomal cytochrome P-450 in rats after 5 or 10 daily 10 mg/kg doses of deltamethrin was ascertained by Habazin-Novak and Plestina (1984). However, a single oral 0.2 LDs0 dose of this compound gave no effect on cytochrome P-450 content (Habazin-Novak et al., 1985). Febacher et al. (1980) found that permethrin given for 3 days in 100 mg/kg oral doses did not induce mixed function oxidase activity in male mice, whereas the results of plasma antipyrine kinetics TABLE 3 HEPATIC MICROSOMAL ENZYMES ACTIVITY IN RATS GIVEN CYPERMETHRIN AND PERMETHRIN
Days
p-Nitroanisole O-demethylase
Aniline 4-hydroxylase
(~zmole/h/100 mg protein)
(l~g/20 min/g tissue)
NADPH Cytochrome P-450 reductase (nmole/min/g protein)
of
dosing 6
10
20
O
C
P
O
C
P
O
C
P
-SD
2.64 0.73
4.70 2.71
3.45 0.97
12.54 3.92
15.96 6.76
12.98 2.59
38.76 10.04
49.79 9.58
45.37 9.03
-+SD
2.37 0.65
2.42 0.68
2.14 0.62
10.87 1.01
10.72 2.34
12.50 2.62
20.36 5.17
26.51 6.79
28.47 × 4.67
_+SD
1.53 0.49
1,48 0,60
2.29 0.94
9.12 1.21
7.89 2.34
12.12 x 1.44
31.24 1.67
34.07 4.03
34.19 5.91
N o t e . Values are mean (E) -+ S.D. (n = 6). x, Significantly different from controls (P < 0.05); C, animals treated with 80 mg/kg of cypermethrin; P, animals treated with 100 mg/kg of permethrin; O, control animals treated with soyabean oil.
EFFECTS OF PYRETHROID INSECTICIDES
133
obtained by Anadon et al. (1988) indicate that permethrin administered for 3 days in 90 and 180 mg/kg doses is capable of producing a dose-dependent enzyme inducing effect. Tang et al. (1987) showed that deltamethrin decreased hepatic microsomal aniline 4-hydroxylase activity and cytochrome P-450 content in male rats. In order to explain the disparities concerning the effects of synthetic pyrethroids on microsomal enzyme activity, cypermethrin, deltamethrin, and permethrin were given to rats in about 0.25 LDs0 oral doses for l to 20 days. The obtained results indicate that only slight changes in the investigated parameters were ascertained. When compared with effects of a strong enzyme inductor, phenobarbital, pyrethroid insecticides exerted a much lower influence on the hepatic microsomal monooxygenases. Whereas phenobarbital increased the activity of several enzymes by about 200% when compared with controls (data not included), synthetic pyrethroids only in one case (p-nitrosole O-demethylase after 6 days of cypermethrin administration) brought about a 70% increase in enzymes activity. The results obtained in this study suggest that the general trend of pyrethroid action on microsomal enzymes is a slight induction. However, a fairly high degree of disparity of results does not generally make this trend statistically significant. To sum up, results derived from our experiments seem to indicate that cypermethrin, deltamethrin, and permethrin administered orally in daily 0.25 LDso doses for up to 20 days do not exert a significant effect on the activity of microsomal enzymes. The observed changes appeared irregularily and had a transient character. So there is no basis to consider synthetic pyrethroids as substances altering the hepatic microsomal enzyme activity. REFERENCES Anadon, A., Diez, M. J., Sierra, M., Sanchez, J. A., and Teran, M. T. (1988). Microsomal enzyme induction by permethrin in rats. Vet. Hum. Toxicol. 30, 30%312. Ellman, G. L. (1959). Tissue sulfhydryl groups. Arch. Biochem. Biophys. 82, 70-77. Febacher, D. L., Kulkarni, A. P., and Hodgson E. (1980). Pesticides as inducers of hepatic drugmetabolizing enzymes. I. Mixed function oxidase activity. Gen. Pharmacol. 11,429-435. Habazin-Novak, V., Fajdetic, T., and Kramaric, M. (1985). Effects of technical malathion and deltamethrin on hepatic microsomal cytochrome P-450 and antipyrine half-life in rats. Yougosl. Physiol. Pharmacol. Acta 21, 14%153. Habazin-Novak, V., and Plestina, R (1984). The effect of deltamethrin on induction of hepatic microsomal cytochrome P-450 in rats. Period. Biol. 86, 315-316. Habig, W. H., Pabst, M. J., and Jakoby, W. B. (1974). Glutathione S-transferase, the first enzymatic step in mercapturic acid formation. J. Biol. Chem. 249, 7130-7139. Kagan, Yu. S., Parishina, T. N., and Sasinovich, L. M. (1986). Biochemical effects of the toxic activity of synthetic pyrethroids Gig. Sanit. 1, 7-9. Kato, R., and Gillette, J. R. (1965). Effects of starvation on NADPH-dependent enzymes in liver microsomes of male and female rats. J. Pharmacol. Exp. Ther. 150, 279-284. Lowry, O. H., Rosenbrough, N. J., Farr, A. L., and Randall, R. J. (1951). Protein measurement with the folin phenol reagent. J. Biol. Chem. 193, 265-275. Masters, B. S. S., Williams, Jr. C. H., and Kamin, H. (1967). The preparation and properties of microsomal TPNH-cytochrome c reductase from pig liver. In "Methods in Enzymology" (R. W. Estabrook and M. E. Pullman, Eds.), Vol. 10, pp. 565-573. Academic Press, New York/London.
134
KRECHNIAK AND WRZEgNIOWSKA
Netter, K. J., and Seidel, G. (1%4). An adaptively stimulated O-demethylating system in rat liver microsomes and its kinetic properties. J. Pharmacol. Exp. Ther. 146, 61-65. Omura, T., and Sato, R. (1964). The carbon monoxide binding pigment of liver microsomes. J. Biol. Chem. 239, 2370--2378. Riviere, J. L., Bach, J., and Grollceau, G. (1983). Effects of pyrethroid insecticides and N(3,5-dichlorophenyl)-dicarboximide fungicides on microsomal-drug metabolizing enzymes in the Japanese quail (Coturnix coturnix). Bull. Environ. Contam. Toxicol. 31, 479-485. Tang, C., Ma, T., and Lin, Y. (1987). Effects of deltamethrin on hepatic microsomal enzymes in rats. Huangjing Kexue Xuebao 7, 175-180.
Effects of Pyrethroid Insecticides on Hepatic Microsomal Enzymes in Rats JERZY KRECHNIAK AND KRYSTYNA WRZEgNIOWSKA
Medical Academy, Department of Toxicology, AI. Hallera 107, 80-416 Gdahsk-Wrzeszcz, Poland Received October 31, 1990 The effects of pyrethroid insecticides on hepatic microsomal enzymes were studied in rats. Animals were treated orally with cypermethrin (80 mg/kg), deltamethrin (15 mg/kg), and permethrin (I00 mg/kg), as a solution in soyabean oil, for 1 to 20 days. The content of cytochromes P-450 and bs, activity of NADPH cytochrome P-450 reductase, glutathione S-transferase, aniline 4-hydroxylase, p-nitroanisote O-demethylase in microsomes, the activity of glutathione S-transferase, and the level of sulfhydryl groups in cytosol were determined. Also the relative liver weight was measured. Only few changes in the investigated parameters were ascertained. These changes have an irregular and transient character. On the whole, the action of pyrethroids on microsomal enzymes results in a slight induction. © 1991AcademicPress,Inc.
INTRODUCTION
A number of pesticides cause various changes in hepatic microsomal enzyme activity. Organophosphate insecticides are generally numbered among moderate inhibitors of microsomal enzyme systems. Prominent among the compounds with microsomal enzymes inducing activity are the chlorinated hydrocarbon insecticides. Experiments performed on pyrethroid insecticides gave different results. Some authors showed that synthetic pyrethroids did not markedly influence the microsomal liver enzymes (Riviere et at., 1983; Habazin-Novak et al., 1985; Febacher et al., 1980); others found an increase (Habazin-Novak and Plestina, 1984; Kagan et al., 1986; Anadon et al., 1988) or decrease (Tang et al., 1987) of their activity. The obtained disparities may result from different methods of pyrethroids administration, various species used in the experiments, as well as different parameters determined. The aim of this study was to investigate the effects of the commonly used pyrethroid insecticides: cypermethrin, deltamethrin, and permethrin on the hepatic microsomal enzymes in rats. MATERIALS AND METHODS Chemicals. The following pyrethroid insecticides were used in this study: cypermethrin--95% purity, obtained from Shell Research Ltd. (Sittingbourne, England); deltamethrin--98% purity, produced by Roussel-Uclaf Romainville, France; permethrin--96% purity, obtained from Wellcome International Trading Ltd. (Berkhamstad Herts, England). A n i m a l s a n d administration. Male albino rats weighing 200 +- 20 g were given daily the following doses of pyrethroids: cypermethrin 80 mg/kg, deltamethrin 15 129 0013-9351/91 $3.00 Copyright© 1991by AcademicPress, Inc. All rightsof reproductionin any formreserved.
130
KRECHNIAK AND WRZEgNIOWSKA
mg/kg, and permethrin 100 mg/kg. The pyrethroids were administered orally as solutions in soyabean oil. Control animals received a corresponding amount of the solvent. Three experiments were performed. In the first one, cypermethrin, deltamethrin, and permethrin were administered up to 4 days; in the second, cypermethrin and deltamethrin were given up to 20 days; in the third, cypermethrin and permethrin were given up to 20 days. M e t h o d s . The day after the administration of the last dose the animals were killed by cervical dislocation. Liver was immediately isolated and the whole tissue homogenized in ice-cooled isotonic potasium chloride---0.01 M phosphate buffer (pH 7.4) was prepared. To obtain the postmitochondrial supernatant, the liver homogenate was centrifuged at 15.000 g for 30 min. The resultant supernatant was centrifuged at 100.000 g for 1 hr in a refrigerated ultracentrifuge to isolate the microsomal fraction. In the postmitochondrial supernatant the activity of 4-nitroanisole O-demethylase (Netter and Seidel, 1964) and aniline 4-hydroxylase (Kato and Gillette, 1965) were determined. In the microsomal fraction the content of cytochromes P-450 and b 5 (Omura and Sato, 1964) and the activity of NADH cytochrome P-450 reductase (Masters et al., 1967) were assessed. The activity of glutathione S-transferase (Habig et al., 1974) was determined in the microsomal and cytosolic fraction. The level of sulfhydryl groups (Ellman, 1959) was assessed in the cytosolic fraction. Protein in the isolated subcellular fractions was determined by the method of Lowry et al. (1951). Statistical analysis was performed using Student's t-test. RESULTS The effects of cypermethrin, deltamethrin, and permethrin given for 1, 2, and 4 days on relative liver weights, the content of cytochromes P-450 and bs, the activity of glutathione S-transferase, and the level of sulfhydryl groups are presented in Table 1. In this experiment only a significant decrease in liver body weight ratio in animals treated with deltamethrin was ascertained. No distinctive influence of the administered pyrethroids on the activity of the investigated enzymes was established. The effects of cypermethrin and deltamethrin administered for 10 and 20 days on relative liver weights, the content of cytochromes P-450 and b5 and the activity of microsomal and cytosolic glutathione S-transferase are presented in Table 2. Statistically significant differences were found only after the administration of pesticides for 20 days. Cypermethrin brought about an increase in the content of cytochrome P-450, deltamethrin in cytochrome bs. Both pyrethroids caused a distinctive decrease in the activity of cytosolic glutathione S-transferase. The effects of cypermethrin and permethrin, given for 6, 10, and 20 days, on the activity of 4-nitroanisole O-demethylase, aniline 4-hydroxylase, and NADPH cytochrome P-450 reductase are presented in Table 3. Permethrin after 10 days of dosing caused a significant increase in the activity of cytochrome P-450 reductase, and after 20 days an increase in the activity of
131
EFFECTS OF PYRETHROID INSECTICIDES
.,-,
o
z
:=1.
exO ~
,0
E~
Z
~E
~
+1
+1
¢-1
132
KRECHNIAK AND WRZEgNIOWSKA
TABLE 2 LIVER WEIGHT AND ACTIVITY OF ENZYMES IN RATS GIVEN CYPERMETHRIN AND DELTAMETHRIN
Cytochrome Days of
dosing 10 20
Glutathione S-transferase (nmole/min/g protein)
Cytochrome
Liver weight (% body weight)
P-450
b5
(nmole/gprotein)
(nmole/gprotein)
O
O
O
C
D
C
D
C
Cytosol
D
O
Microsomes
C
D
O
C
D
-SD
3.3 3.7 3.8 0.47 0 . 5 0 0.54 0 . 4 3 0 . 3 5 0.11 0.08
0 . 3 4 0 . 2 0 0 . 2 6 0 . 1 8 78.3 6 5 . 6 0.11 0 . 0 4 0.11 0 . 0 6 23.9 16.4
7 0 . 3 3.30 3.35 3.02 10.8 1.26 1.73 1.33
-SD
3.4 3.3 3.8 0.46 0.62x 0.45 0 . 4 8 0.43 0 . 0 4 0 . 1 0
0 . 5 4 0 . 3 4 0.31 0.52x 76.5 49.6xx 53.7x 3.40 2.99 3.35 0 . 1 0 0.11 0.11 0 . 1 2 14.3 14.5 10.1 1.38 1.48 1.83
Note. Values are mean ~ -+ S.D. (n = 6). x, Significantly different from controls (P < 0.05); xx, significantly different from controls (P < 0.005); C, animals treated with 80 mg/kg of cypermethrin; D, animals treated with 15 mg/kg of deltamethrin; O, control animals treated with soyabean oil.
aniline 4-hydroxylase. No significant changes in the activity of the investigated enzymes were found in animals treated with cypermethrin. DISCUSSION
The effects of different pyrethroid insecticides on hepatic microsomal enzyme activity have been examined by several authors. Riviere et al. (1983) found that permethrin, cypermethrin, deltamethrin, and fenvalerate gave no or only a moderate increase in hepatic microsomal cytochrome P-450 level and NADPH cytochrome P-450 reductase activities in the Japanese quail. A significant increase in hepatic microsomal cytochrome P-450 in rats after 5 or 10 daily 10 mg/kg doses of deltamethrin was ascertained by Habazin-Novak and Plestina (1984). However, a single oral 0.2 LDs0 dose of this compound gave no effect on cytochrome P-450 content (Habazin-Novak et al., 1985). Febacher et al. (1980) found that permethrin given for 3 days in 100 mg/kg oral doses did not induce mixed function oxidase activity in male mice, whereas the results of plasma antipyrine kinetics TABLE 3 HEPATIC MICROSOMAL ENZYMES ACTIVITY IN RATS GIVEN CYPERMETHRIN AND PERMETHRIN
Days
p-Nitroanisole O-demethylase
Aniline 4-hydroxylase
(~zmole/h/100 mg protein)
(l~g/20 min/g tissue)
NADPH Cytochrome P-450 reductase (nmole/min/g protein)
of
dosing 6
10
20
O
C
P
O
C
P
O
C
P
-SD
2.64 0.73
4.70 2.71
3.45 0.97
12.54 3.92
15.96 6.76
12.98 2.59
38.76 10.04
49.79 9.58
45.37 9.03
-+SD
2.37 0.65
2.42 0.68
2.14 0.62
10.87 1.01
10.72 2.34
12.50 2.62
20.36 5.17
26.51 6.79
28.47 × 4.67
_+SD
1.53 0.49
1,48 0,60
2.29 0.94
9.12 1.21
7.89 2.34
12.12 x 1.44
31.24 1.67
34.07 4.03
34.19 5.91
N o t e . Values are mean (E) -+ S.D. (n = 6). x, Significantly different from controls (P < 0.05); C, animals treated with 80 mg/kg of cypermethrin; P, animals treated with 100 mg/kg of permethrin; O, control animals treated with soyabean oil.
EFFECTS OF PYRETHROID INSECTICIDES
133
obtained by Anadon et al. (1988) indicate that permethrin administered for 3 days in 90 and 180 mg/kg doses is capable of producing a dose-dependent enzyme inducing effect. Tang et al. (1987) showed that deltamethrin decreased hepatic microsomal aniline 4-hydroxylase activity and cytochrome P-450 content in male rats. In order to explain the disparities concerning the effects of synthetic pyrethroids on microsomal enzyme activity, cypermethrin, deltamethrin, and permethrin were given to rats in about 0.25 LDs0 oral doses for l to 20 days. The obtained results indicate that only slight changes in the investigated parameters were ascertained. When compared with effects of a strong enzyme inductor, phenobarbital, pyrethroid insecticides exerted a much lower influence on the hepatic microsomal monooxygenases. Whereas phenobarbital increased the activity of several enzymes by about 200% when compared with controls (data not included), synthetic pyrethroids only in one case (p-nitrosole O-demethylase after 6 days of cypermethrin administration) brought about a 70% increase in enzymes activity. The results obtained in this study suggest that the general trend of pyrethroid action on microsomal enzymes is a slight induction. However, a fairly high degree of disparity of results does not generally make this trend statistically significant. To sum up, results derived from our experiments seem to indicate that cypermethrin, deltamethrin, and permethrin administered orally in daily 0.25 LDso doses for up to 20 days do not exert a significant effect on the activity of microsomal enzymes. The observed changes appeared irregularily and had a transient character. So there is no basis to consider synthetic pyrethroids as substances altering the hepatic microsomal enzyme activity. REFERENCES Anadon, A., Diez, M. J., Sierra, M., Sanchez, J. A., and Teran, M. T. (1988). Microsomal enzyme induction by permethrin in rats. Vet. Hum. Toxicol. 30, 30%312. Ellman, G. L. (1959). Tissue sulfhydryl groups. Arch. Biochem. Biophys. 82, 70-77. Febacher, D. L., Kulkarni, A. P., and Hodgson E. (1980). Pesticides as inducers of hepatic drugmetabolizing enzymes. I. Mixed function oxidase activity. Gen. Pharmacol. 11,429-435. Habazin-Novak, V., Fajdetic, T., and Kramaric, M. (1985). Effects of technical malathion and deltamethrin on hepatic microsomal cytochrome P-450 and antipyrine half-life in rats. Yougosl. Physiol. Pharmacol. Acta 21, 14%153. Habazin-Novak, V., and Plestina, R (1984). The effect of deltamethrin on induction of hepatic microsomal cytochrome P-450 in rats. Period. Biol. 86, 315-316. Habig, W. H., Pabst, M. J., and Jakoby, W. B. (1974). Glutathione S-transferase, the first enzymatic step in mercapturic acid formation. J. Biol. Chem. 249, 7130-7139. Kagan, Yu. S., Parishina, T. N., and Sasinovich, L. M. (1986). Biochemical effects of the toxic activity of synthetic pyrethroids Gig. Sanit. 1, 7-9. Kato, R., and Gillette, J. R. (1965). Effects of starvation on NADPH-dependent enzymes in liver microsomes of male and female rats. J. Pharmacol. Exp. Ther. 150, 279-284. Lowry, O. H., Rosenbrough, N. J., Farr, A. L., and Randall, R. J. (1951). Protein measurement with the folin phenol reagent. J. Biol. Chem. 193, 265-275. Masters, B. S. S., Williams, Jr. C. H., and Kamin, H. (1967). The preparation and properties of microsomal TPNH-cytochrome c reductase from pig liver. In "Methods in Enzymology" (R. W. Estabrook and M. E. Pullman, Eds.), Vol. 10, pp. 565-573. Academic Press, New York/London.
134
KRECHNIAK AND WRZEgNIOWSKA
Netter, K. J., and Seidel, G. (1%4). An adaptively stimulated O-demethylating system in rat liver microsomes and its kinetic properties. J. Pharmacol. Exp. Ther. 146, 61-65. Omura, T., and Sato, R. (1964). The carbon monoxide binding pigment of liver microsomes. J. Biol. Chem. 239, 2370--2378. Riviere, J. L., Bach, J., and Grollceau, G. (1983). Effects of pyrethroid insecticides and N(3,5-dichlorophenyl)-dicarboximide fungicides on microsomal-drug metabolizing enzymes in the Japanese quail (Coturnix coturnix). Bull. Environ. Contam. Toxicol. 31, 479-485. Tang, C., Ma, T., and Lin, Y. (1987). Effects of deltamethrin on hepatic microsomal enzymes in rats. Huangjing Kexue Xuebao 7, 175-180.
