The effect of basic cupric acetate on the activities of the drug metabolizing enzymes was studied. When basic cupric acetate was administered with and without DAB to the rat, the overall activity of the DAB metabolizing enzyme system was increased remarkably, which was mainly ascribed to the enhancement of the azo-reduction. The activity of azo-reduction was reduced a little by the administration of DAB alone. The activity of N-demethylation was reduced a little by the administration of copper, but by the administration of DAB alone the activity appeared to increase a little. The administration of copper and DAB did not affect the activity of aromatic hydroxylation. One role of copper which retards the hepatic carcinogenesis by DAB might be related to the enhancement of the activity of azo-reduction, which detoxicates the carcinogenic dye to the noncarcinogenic compounds.
