Effects of aflatoxin B1 on the hepatic microsomal mixed function oxidase system during phenobarbital and benzo(a)pyrene treatment in chickens.

Administration of 1.5 mg aflatoxin B1 (AFB1)/kg in DMSO as a single i.p. dose to 80 mg phenobarbital/kg i.p. for 3 d pretreated chickens showed significant decrease in the levels of electron transport components and drug metabolizing enzymes compared to phenobarbital administration alone. Induction of mixed function oxidase enzymes due to phenobarbital was not affected by the AFB1 pretreatment. AFB1 administration to 20 mg benzo(a)pyrene/kg in safflower seed oil i.p. for 2 d pretreated chickens showed significant decrease in cytochrome b5 and drug metabolizing enzymes when compared with benzo(a)pyrene treatment alone. However, cytochrome P450 level was slightly higher due to administration of AFB1 to benzo(a)pyrene-injected chickens. The results indicate that the phenobarbital-induced cytochrome P450 is more susceptible to AFB1 than benzo(a)pyrene-induced cytochrome P450.