A STUDY INTO THE EFFECTS OF 2-ACETYLAMINOFLUORENE ON HEPATIC MONOOXYGENASE ACTIVITIES IN THE CHICK-EMBRYO

2AAF [2-acetylaminofluorene] is a potent inducer of cytochrome P-450 in the chick embryo liver. The induction was characterized with respect to a range of monooxygenase activities and the regiospecificity of 2AAF hydroxylation. Similarities to the response elicited by both PB and 3MC [phenobarbital and 3-methylcholanthrene] were noted. 2AAF was rapidly deacetylated by hepatic microsomes prepared from control animals to 2AF, an inhibitor of monooxygenase activity. Metabolites generated in vivo and carried over in vitro might have therefore interfered with the subsequent kinetic analysis. In general terms induction of a unique cytochrome P-450 subform(s) could not be attributed to 2AAF in the chick embryo. The data is discussed with respect to the reported resistance of avian species to the hepatocarcinogenic effects of 2AAF. Two possibilities are highlighted, a diversion of 2AAF to ring hydroxylated metabolites and/or deacetylation of 2AAF. Both effects could reduce carcinogenicity by decreasing the concentration of proximate carcinogen and/or promoter(s).