Comparative metabolism of benzo[ƒ]quinoline by liver microsomes from brown bullheads and rats

1. Liver microsomes from rats were considerably more active in metabolizing benzo[f{hook}]quinoline (B f{hook} Q) than those from brown bullheads (Ictalurus nebulosus). 2. The main B f{hook} Q metabolites formed by both rat and brown bullhead liver microsomes were qualitatively similar and included B f{hook} Q-7,8-dihydrodiol, B f{hook} Q-9,10-dihydrodiol, B f{hook} Q-N-oxide, 7-hydroxy B f{hook} Q, and 9-hydroxy B f{hook} Q. 3. The liver microsomes from control brown bullheads and rats metabolized B f{hook} Q primarily at the 7,8-and 9,10-positions, respectively, whereas in the case of microsomes from 3-methylcholanthrene (3-MC)-treated rats or brown bullheads, the major site of metabolic attack was the 7,8-position. 4. A 3-MC-type of cytochrome P-450 appears to be primarily responsible for the oxidation of B f{hook} Q by control brown bullhead liver microsomes, whereas a phenobarbital-inducible type of cytochrome P-450 seems to be involved in the metabolism of B f{hook} Q by control rat liver microsomes.