title: Formation of benzo(a)pyrene/DNA adducts and their relationship to tumor initiation in mouse epidermis.
abstract: The tumorigenicity of benzo(a)pyrene [B(a)P] applied topically as a skin tumor initiator in Sencar mice and the formation of epidermal B(a)P/deoxyribonucleoside adducts were compared over a similar range of doses (50 to 1600 nmol). The tumor-initiating activity of B(a)P, its covalent binding to mouse epidermal DNA, and the formation of the major hydrocarbon/deoxyribonucleoside adduct showed approximately parallel dose-response curves. The major hydrocarbon/deoxyribonucleoside adduct formed cochromatographed with marker adducts of (N2-(10S-[7R,8S,9R-trihydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene]y) deoxyguanosine while other minor adducts also were observed. The disappearance of DNA-bound products in the epidermis was followed for 21 days after an initiating dose of B(a)P (100 nmol) was applied topically to the mice. The half-lives of the B(a)P/deoxyribonucleoside adducts and the total radioactivity bound to the DNA were 4.5 and 5.5 days, respectively. However, in spite of the loss of measurable DNA-bound material, the tumor yield was unchanged regardless of whether promotion was begun 7 or 21 days after initiation. The results suggest a possible causal relationship between B(a)P/deoxyribonucleoside adduct formation and papilloma formation in mouse skin.
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene; D001580:Benzopyrenes / Q000378:metabolism* / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004817:Epidermis / Q000187:drug effects / Q000378:metabolism; D006207:Half-Life; D051379:Mice; D012878:Skin Neoplasms / Q000139:chemically induced*; D013997:Time Factors
chemical_list: D001580:Benzopyrenes; D001564:Benzo(a)pyrene; D004247:DNA