Benzo(a)pyrene diol epoxide-I-DNA adduct formation in the epidermis and lung of SENCAR mice following topical application of crude coal tar.

The levels of benzo[a]pyrene diol epoxide-I-deoxyguanosine (BPDE-I-dG) adduct formation in epidermis and lung of SENCAR mice following the topical application of benzo[a]pyrene (BP) alone, crude coal tar (CCT) alone, and the two combined were determined in an enzyme linked immunosorbent (ELISA) assay using monoclonal antibodies. Topical application of two doses of BP (20 micrograms) at 72-h intervals, with sacrifice 24 h later resulted in the formation of 197 fmol and 205 fmol BPDE-I-dG adducts per mg DNA in epidermis and lung, respectively. Topical application of 0.5 ml CCT alone resulted in the formation of 278 fmol and 410 fmol BPDE-I-dG adducts per mg DNA in epidermis and lung, respectively. Simultaneous topical application of 20 micrograms BP and CCT (0.1-0.5 ml) resulted in substantially lower BPDE-I-dG adducts in the epidermis as well as in the lung. Our results suggest that CCT may contain inhibitors of carcinogen-DNA adduct formation and that topical application of CCT produces greater effects on DNA-adduct formation in lung than in epidermis. Thus the cancer-causing potency of the polycyclic aromatic hydrocarbons (PAHs) in CCT may be reduced by other anticarcinogenic constituents present in CCT and systemic absorption of carcinogenic PAHs in CCT applied to skin might have tumorigenic effects in other tissues.