Aflatoxin induces depletion of activities of phase I biotransformation enzymes in growing rats.

Aflatoxins are suspected human carcinogens and are also known to possess diverse toxicological activities. In the present communication an attempt has been made to evaluate the effects of aflatoxin B1 (AFB1) on hepatic microsomal drug metabolizing enzymes in growing rats. The weanling rats were exposed to 60, 300 or 600 micrograms AFB1/kg body weight, per os, on alternate days for 4 weeks, in 0.2 ml corn oil. A significant depression in the activities of aryl hydrocarbon hydroxylase (AHH), aniline hydroxylase (AH) and aminopyrene-N-demethylase (AND) was observed at 300 micrograms and 600 micrograms doses of AFB1. However, no significant change was recorded in glutathione-S-transferase (GST) activity and total sulphydryl (SH) content upon AFB1 exposure in weanling rats. Thus, AFB1 appears to have more pronounced effect on the phase I, rather than phase II, biotransformation enzyme system in weanling rats. The depression of drug metabolizing enzymes together with suppression of immunity by AFB1, as reported earlier by us, may increase the susceptibility of the host to toxic chemicals, drugs and infectious agents, particularly during the post-natal period.