The hepatic microsomal metabolism of the carcinogenic 8-methylquinoline (8MQ) and its noncarcinogenic isomer, 6-methylquinoline (6MQ), were compared for preparations from control rats and rats pretreated with phenobarbital or 3-methylcholanthrene. For each compound the alcohol was the major metabolite, constituting 50-75% of 6MQ metabolites and 60-85% of 8MQ metabolites. Three phenols for 6MQ and two for 8MQ were seen. The latter formed two dihydrodiols which constituted 1-5% of metabolites while dihydrodiol products were not identified for the nontumorigenic 6MQ. Epoxides were observed for 6MQ while 8MQ afforded an N-oxide.
