Species Difference among Experimental Rodents in the Activity and Induction of Cytochrome P‐450 Isozymes for Mutagenic Activation of Carcinogenic Aromatic Amines

The expressions of hepatic microsomal cytochrome P‐450 isozymes in male rats, mice, hamsters and guinea pigs were studied comparatively with or without an ip injection of a cytochrome P‐450 inducer. The activity and quantity of microsomal cytochrome P‐450 isozymes were determined respectively by a bacterial mutation assay with Salmonella typhimurium TA98 and immunochemical assays using monoclonal antibodies against rat cytochrome P‐450 isozymes. 3‐Methoxy‐4‐aminoazobenzene (3‐MeO‐AAB), 2‐amino‐3‐methyl‐9H‐pyrido[2,3‐b]indole acetate (MeAαC) and 3‐methylcholanthrene were used as cytochrome P‐450 inducers, and 7 carcinogenic aromatic amines including 3‐MeO‐AAB and MeAαC were used as substrates for the mutation assay. By means of these assays, we examined the species differences among rodents in the activity and induction rate of hepatic cytochrome P‐450 isozymes responsible for the mutagenic activation of carcinogenic aromatic amines.