The metabolic activation of dibenz[a,h]anthracene in mouse skin examined by 32P-postlabelling: minor contribution of the 3,4-diol 1,2-oxides to DNA binding.

Dibenz[a,h]anthracene (DB[a,h]A) and the related 3,4-diol and anti- and syn-3,4-diol 1,2-oxides were applied to the shaved dorsal skin of groups of four C57Bl/CB1 mice. Twenty-four hours later the mice were killed, DNA isolated from the treated skin, hydrolysed and examined for the presence of aromatic adducts using the nuclease P1 modification of the 32P-postlabelling technique. Autoradiography of the maps obtained by chromatography on polyethyleneimine-cellulose plates showed that six DNA adduct spots that were derived from DB[a,h]A were also present in the DNA of skin treated with the DBA 3,4-diol and that, whilst four of these adduct spots were also seen in maps prepared from the DNA of skin treated with the anti-3,4-diol-1,2-oxide, they were not present in DNA from skin to which the syn-isomer had been applied. The identity of these adduct spots was confirmed by their coincidence when mixtures of different DNA hydrolysates were chromatographed together. Quantitatively, the highest levels of mouse skin modification were obtained with the diol-epoxides and the lowest with DB[a,h]A. The results suggest that most of the DNA adducts formed in DB[a,h]A-treated mouse skin arise through metabolism of the hydrocarbon to the related 3,4-diol and that some may be formed following the conversion of this diol to the bay-region anti-3,4-diol-1,2-oxide.