Effects of Benomyl on Cytochrome P450 Monooxygenase Systems in the Hep G2 Cell Line

Changes in the cytochrome P450 monooxygenase system were investigated in Hep G2 cells treated for 24 hours with various concentrations of benomyl. Decreases in both benzo[a]pyrene hydroxylase (AHH) and ethoxyresorufin deethylase (EROD), markers of the P4501A1 isoenzyme, were noted. Ethoxycoumarin deethylase (ECOD), a marker of the P4502B1 isoenzyme, showed a dose-dependent increase. Characterisation by SDS-polyacrylamide gel electrophoresis of Hep G2 cell microsomal proteins revealed a decrease in the polypeptide bands at 55.5kD (P4501A1) and 48kD (P4501A1 and P4502B1) and an increase in the polypeptide band at 52kD (P4502B1). Benomyl induced a decrease in cytochrome P4501A1 and an increase in cytochrome P4502B1 in Hep G2 cells, as indicated by variations in AHH, EROD and ECOD activity, and by characterisation of microsomal proteins by SDS-polyacrylamide gel electrophoresis.