Effects of pyrethroid insecticides on hepatic microsomal enzymes in rats.

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 (100 mg/kg), as a solution in soyabean oil, for 1 to 20 days. The content of cytochromes P-450 and b5, activity of NADPH cytochrome P-450 reductase, glutathione S-transferase, aniline 4-hydroxylase, p-nitroanisole 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.