N-benzylimidazole, a high magnitude inducer of rat hepatic cytochrome P-450 exhibiting both polycyclic aromatic hydrocarbon- and phenobarbital-type induction of phase I and phase II drug-metabolizing enzymes.

The effects of N-benzylimidazole on hepatic microsomal and cytosolic drug-metabolizing enzymes were compared to the effects produced by phenobarbital, beta-naphthoflavone, a polycyclic aromatic hydrocarbon, and Aroclor 1254, a polychlorinated biphenyl mixture. N-Benzylimidazole was a "high magnitude" inducer of male rat hepatic cytochrome P-450, inducing cytochrome P-450 over 3 times above control. N-Benzylimidazole exhibited mixed type induction of cytochrome P-450, producing both polycyclic aromatic hydrocarbon- and phenobarbital-type induction. There was no evidence of imidazole (isoniazid) type induction characteristics. Microsomes from rats treated with either Aroclor 1254 or N-benzylimidazole showed a common pattern of induction of the cytochrome P-450-dependent properties and glucuronosyltransferase activities, and the electrophoretic profiles of proteins were also similar. Cytosolic glutathione transferase activity was also induced similarly after treatment with the two agents.