Epoxides as microsomal metabolites of polycyclic hydrocarbons

The main metabolites of polycyclic hydrocarbons are hydroxylated derivatives [ 1] . These could theoretically arise from epoxide intermediates [2] formed by the NADPHdependent microsomal mixed function oxidase. K-region epoxides of polycyclic hydrocarbons that have been prepared synthetically [3] have been shown to be alkylating agents that react covalently with nucleic acids [4] and with the constituents of cells in culture [S] . These K-region epoxides are also mutagenic to T, bacteriophage [6] , to bacteria [7] , to Drosophila [8] and to Chinese hamster cells [9] and are active in producing malignant transformation of cells in culture [lo]. Consequently, it seemed important to establish that epoxides are in fact involved in the metabolism of polycyclic hydrocarbons. In the experiments described here, direct evidence has been obtained that epoxides are formed as microsomal metabolites of phenanthrene, benz[a] anthracene and dibenz[a,hh] anthracene.