Age-related effects in the inhibition of oxidative metabolism of xenobiotics by mancozeb.

The effect of po administration of 100 or 200 mg mancozeb/kg body weight for 7 consecutive days on microsomal mixed-function oxidase catalyzed xenobiotic metabolism was investigated in the livers of newborn weanling and adults rats. Mancozeb caused a dose-dependent inhibition in the activities of p-nitroanisole O-dealkylase and aniline hydroxylase, while the activities of aminopyrine N-demethylase and benzo(a)pyrene hydroxylase were unaffected in all the age groups. The inhibition of p-nitroanisole O-dealkylase and aniline hydroxylase, was remarkably higher in adult than in newborn and weanling rats. There was a concentration-dependent decrease in cytochrome P-450 and microsomal protein contents. This study indicates selective age-independent inhibition of hepatic monooxygenases following repeated mancozeb dosing.