Monoclonal antibody characterization of NADH- and NADPH-dependent hydroxylation of benzo(a)pyrene in liver microsomes from 5,6-benzoflavone-induced C57Bl/6 mice.

Monoclonal antibodies (MAb 1-7-1) directed against the isoenzymes of rat liver cytochrome P-450 induced by methylcholanthrene, inhibited benzo(a)pyrene hydroxylase less strongly at low (0.04 mM) than at high (2 mM) NADH concentration. Inhibition of NADPH dependent hydroxylation was the same irrespective of NADPH concentrations and corresponded to that observed at high NADH concentration. The same was also the h.p.l.c. pattern of the reaction products of benzo(a)pyrene hydroxylation supported by high concentration of both coenzymes. It is postulated that different cytochrome P-450 isoenzymes participate in benzo(a)pyrene hydroxylation, whereas the second one acts at high concentration of both NADH and NADPH.