The role of 9-hydroxybenzo(a)pyrene in the microsome mediated binding of benzo(a)pyrene to DNA

A study of the liver microsome-mediated binding to added DNA of the phenol metabolites of benzo(a)pyrene (BP-OH) and of 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene (BP-7,8-diol) suggested that as in the case of BP itself the reaction was catalysed by the enzyme aryl hydrocarbon hydroxylase. The addition of glutathione to the microsomal incubation inhibited the binding of BP and BP-OH more than that of BP-7,8-diol. Analysis by LH20 chromatography of the deoxyribonucleoside products from BP-DNA showed greater inhibition by glutathione of formation of the major product believed to result from further metabolism of BP-OH, than of the product arising by metabolism of BP-7,8-diol. The chromatographic behaviour and fluorescence spectrum of this major product were consistent with its derivation from 9-hydroxybenzo(a)pyrene (BP-9-OH) and furthermore suggested that BP-9-OH-4,5-oxide was the derivative whose reaction with DNA yielded this microsome-mediated BP-DNA product.