Position-specific induction of benzo(a)pyrene metabolism by 3-methylcholanthrene and phenobarbital in mullet (Mugil cephalus), a marine fish.

Mullet (Mugil cephalus), a marine fish, were treated with 3-methylcholanthrene and phenobarbital by i.p. injection and the effects on the metabolism of benzo(a)pyrene by isolated liver microsomes were evaluated. The most significant effect found in treated fish was an increase in the oxidation of benzo(a)pyrene at the bay region, a position-specific increase which was not reflected in an increase in the total activity. Comparison of metabolite patterns of the dihydrodiols of benzo(a)pyrene in the presence and absence of trichloropropene oxide showed that predicted inhibitions were observed in control as well as treated animals. No significant differences in metabolite patterns were found between the 3-methylcholanthrene- and phenobarbital-treated fish in either the presence or absence of trichloropropene oxide. Comparison is made to published data on similar position-specific effects observed in rats.