Microsomal hydroxylation of 3-methylcholanthrene: analysis by computerized gas chromatography-mass spectrometry.

Microsomal metabolism of 3-methylcholanthrene (MC) was examined by computerized gas chromatography-mass spectrometry. Five mono-, four di- and thirteen trihydroxylated metabolites were found after incubation of MC in mouse liver microsomal fraction for 15 min, in the presence of NADPH. Among these metabolites, three mono- and three dihydroxylated metabolites were identified by means of authentic samples. The chemical structures of the other metabolites were deduced from their characteristic mass spectral fragmentations. This is the first description of trihydroxylated metabolites in MC metabolism in vitro and in vivo.