Evidence that binding of 7,12-dimethylbenz(a)anthracene to DNA in mouse embryo cell cultures results in extensive substitution of both adenine and guanine residues.

Primary mouse embryo cell cultures were grown in the presence of [14C]guanine, labeling primarily deoxyguanosine residues in the cellular DNA, or in the presence of [14C]adenine, labeling both deoxyguanosine and deoxyadenosine residues in the cellular DNA. These cultures were subsequently exposed to 7,12-[3H]dimethylbenz(a)anthracene for 24 hr. The DNA was isolated and hydrolyzed to deoxyribonucleosides, and the 7,12-dimethylbenz(a)anthracene:deoxyribonucleoside adducts were separated chromatographically allowing the three major adducts found to be identified as bay-region anti-dihydrodiol-epoxide:deoxyguanosine and :deoxyadenosine adducts and a bay-region syn-dihydrodiol-epoxide:deoxyadenosine adduct. Therefore, in contrast to what is known for benzo(a)pyrene, substantial amounts of deoxyadenosine adducts are formed with the more potent carcinogen, 7,12-dimethylbenz(a)anthracene.