On the metabolic activation of benz[a]acridine and benz[c]acridine by rat liver and lung microsomes.

The metabolism of benz[a]- and benz[c]acridine by liver and lung microsomes from untreated, phenobarbital (PB)-treated and benzo[k]fluoranthene (BkF)-treated rats has been studied by gas chromatography/mass spectrometry (GC/MS). Epoxidation and hydrolysis of the epoxides to dihydrodiols were found to be the predominant pathways for all substrates. N-Oxidation is likely to occur in the case of benz[c]acridine. However, no unequivocal evidence could be obtained for the formation of the ultimate carcinogens--the t-3,4-dihydrodiol-1,2-epoxides--in case of both benz[a]- and benz[c]acridine. K-Region oxidation was induced by phenobarbital, whereas the formation of non-K-region metabolites increased after BkF treatment in the case of benz[c]acridine.