Binding to DNA of bay region and pseudo bay region diol-epoxides of dibenzo[a,e]fluoranthene and comparison with adducts obtained with dibenzo[a,e]fluoranthene or its dihydrodiols in the presence of microsomes.

When dibenzo[a,e]fluoranthene (DBF) is incubated in vitro with mouse liver microsomes in the presence of calf thymus DNA, several metabolites bind covalently to DNA. The metabolite-nucleoside adducts were separated by h.p.l.c. after enzymatic hydrolysis. The elution profile of this chromatogram exhibits six main peaks, labeled from A to F in order of decreasing polarity. It was compared to those obtained by direct reaction of DNA with 3,4-dihydroxy-1,2-epoxy 1,2,3,4-tetrahydro DBF (the bay region diol-epoxide) or 12,13-dihydroxy 10,11-epoxy 10,11,12,13-tetrahydro DBF (the pseudo bay region diol-epoxide). In both cases the retention period of the peak of the adduct was identical to that of the main peak E. The fluorescence spectra of these two adducts were similar to those of the corresponding tetrols. When DNA is reacted in the presence of microsomes with 3,4-dihydrodihydroxy DBF, the elution profile of the adducts indicates that vicinal epoxidation of the dihydrodiol and direct reaction is dominant. The metabolic reaction with 12,13-dihydrodihydroxy DBF appears more complex as revealed by the observed number of adducts which correspond to vicinal epoxidation of dihydrodiol as well as further oxidation at other sites.