Identification of the mutagenic metabolites of fluoranthene, 2-methylfluoranthene, and 3-methylfluoranthene

The metabolites of fluoranthene, 2-methylfluoranthene, and 3-methylfluoranthene obtained upon incubation with liver homogenate from Aroclor pretreated rats were assayed for mutagenicity in Salmonella typhimurium TA100. The mutagenic metabolites of fluoranthene and 2-methylfluoranthene were identified as 2,3-dihydro-2,3-dihydroxyfluoranthene and 4,5-dihydro-4,5-dihydroxy-2-methylfluoranthene, respectively. In contrast to these results, the major proximate mutagen detected among the in vitro metabolites of 3-methylfluoranthene was 3-hydroxymethylfluoranthene. Comparison of the mutagenic potential of 2-hydroxymethylfluor-anthene demonstrated that the latter was a more powerful mutagen. Quantitative analyses of the metabolites of fluoranthene with that of 3-hydroxymethylfluoranthene demonstrated that the latter was a more powerful mutagen. Quantitative analyses of the metabolites of fluoranthene, 2-methylfluoranthene, and 3-methylfluoranthene indicated that similar amounts of dihydrodiols were formed. 4,5-Dihydro-4,5-dihydoxy-3-methylfluoranthene, however, was not found to be a potent mutagenic metabolite. These data suggest that the activation pathway to ultimate mutagens may differ for 2- and 3-methylfluoranthene.