The in vitro metabolism and covalent binding of benzo[ a]pyrene to dna catalysed by trout liver microsomes

Abstract

Summary Aryl hydrocarbon ( benzo[ a ]pyrene) hydroxylase activity (EC 1.14.14.2) and the binding of benzo[ a ]pyrene metabolites to deproteinized DNA in vitro and both about 3–4 times higher in trout liver microsomes than in control rat liver microsomes. The hydroxylase activity and the DNA binding with liver microsomes from 3-methylcholanthrene (MC) treated rats are about 10 and 36 times, respectively, greater than in control rat liver microsomes. The liver microsomes from another fresh-water fish (roach) are relatively inactive, the enzyme activity about 7% and the DNA binding 11% of that in control rat liver microsomes. Several BP metabolite-nucleoside complexes were resolved with a Sephadex LH-20 column chromatography in samples with rat and trout liver microsomes. There are no discernible peaks with roach liver microsomes. With rat liver microsomes, more than ten peaks are detectable, the most prominent being peaks associated with benzo[ a ]pyrene-diol-epoxide and benzo[ a ]pyrene-phenols. The same peaks are highest with trout liver microsomes. The benzo[ a ]pyrene metabolite patterns with trout or 3-MC-induced rat liver microsomes show a predominance of non-K-region metabolites, compared with control rat liver microsomes. These results show that the formation of different reactive benzo[ a ]pyrene intermediates which bind covalently to DNA is very similar between 3-MC-treated rat and untreated trout liver microsomes.