Benzo(a)pyrene metabolism in hepatic microsomes from feral and 3-methycholanthrene-treated southern flounder, Paralichthys lethostigma.

Benzo(a)pyrene hydroxylase (AHH) activities were measured in hepatic microsomes from untreated and 3-methylcholanthrene (3-MC) treated southern flounder (Paralichthys lethostigma). The AHH activities of only three of the feral animals appeared to be uninduced, i.e., AHH activities were very low (14 to 22 pmol/min/mg protein) and were stimulated approximately 2-fold by 7,8-benzoflavone (7,8-BF)-in vitro. All remaining untreated animals had higher AHH activities (72 to 623 pmol/min/mg) which were markedly inhibited by 7,8-BF (78.2 +/- 3.0%). These fish were much more similar to the 3-MC induced fish (843 +/- 120 pmol/min/mg and 81% inhibition by 7,8-BF) than to the uninduced animals. However, all three groups (feral with low AHH activity, feral with high AHH activity and 3-MC treated) showed very similar patterns of benzo(a)pyrene (BP) metabolism with a marked preference for benzo-ring oxidation (60% of total metabolites). The pattern of BP metabolism in flounder is in marked contrast to that of the control rat, but is similar to that of the 3-MC induced rat. These results suggest that, at least in the pattern of BP metabolism, flounder hepatic microsomes and their constitutive cytochromes P-450 from untreated and polycyclic hydrocarbon induced fish are similar to rat hepatic cytochromes P-450 induced by polycyclic aromatic hydrocarbon administration.