Comparative metabolism of benzo[a]pyrene by liver microsomes of channel catfish and brown bullhead

We investigated the metabolism of the carcinogen benzo[a]pyrene (BaP) by liver microsomes of channel catfish (Ictalurus punctatus) and brown bullhead (Ameiurus nebulosus) pretreated with 3-methylcholanthrene. The catfish liver microsomes metabolized BaP at a considerably lower rate than did the brown bullhead liver microsomes. Although the BaP metabolites produced by the liver microsomes of the two species were qualitatively similar, there were considerable differences in the relative proportions of individual metabolites formed. The catfish liver microsomes produced a considerably lower proportion of benzo-ring diols of BaP including BaP-7,8-diol (the proximate carcinogenic metabolite of BaP) than did the bullhead liver microsomes. Compared to the bullhead liver microsomes, the catfish microsomes converted a higher proportion of BaP to phenolic metabolites.