title: 5-Methylchrysene metabolism in mouse epidermis in vivo, diol epoxide--DNA adduct persistence, and diol epoxide reactivity with DNA as potential factors influencing the predominance of 5-methylchrysene-1,2-diol-3,4-epoxide--DNA adducts in mouse epidermis.
abstract: 5-Methylchrysene (5-MeC) can form two bay region dihydrodiol epoxides: 1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (DE-I) which has the methyl group and the epoxide ring in the same bay region, and 7,8-dihydroxy-9,10-epoxy-7,8,10-tetrahydro-5-methylchrysene (DE-II). In a previous study, we observed that the ratio of DE-I:DNA adducts to DE-II:DNA adducts in mouse epidermis, 24 h after application of [3H]5-MeC metabolites was 2.7 to 1. To investigate the basis for this observation we have now studies: (i) the formation of [3H]5-MeC in mouse epidermis in vivo at various time intervals from 0.33 to 24 h; (ii) the persistence of DE-I:DNA adducts and DE-II:DNA adducts in mouse epidermis at 4-48 h after application of [3H]5-MeC; and (iii) the reactions of DE-I and DE-II with calf thymus DNA in vitro. In contrast to results obtained with mouse liver 9000 grams supernatant, the dihydrodiol precursors of DE-I and DE-II were present in equivalent quantities in mouse epidermis in vivo at every time point studied. The ratio of DE-I:DNA adducts to DE-II:DNA adducts in mouse epidermis was constant throughout the time period studied. However, the extent of formation of DE-I:DNA adducts was greater than that of DE-II:DNA adducts upon reaction of DE-I or DE-II with calf thymus DNA in vitro. These results suggest that differences in reactivity with DNA of DE-I and DE-II may bw responsible for the higher levels in mouse epidermis of DE-I:DNA adducts compared with DE-II:DNA adducts and provide a possible basis for the observed enhancing effect of a bay region methyl group on the carcinogenicity of polynuclear aromatic hydrocarbons.
mesh_terms: D000818:Animals; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism*; D002911:Chrysenes / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004852:Epoxy Compounds / Q000378:metabolism*; D004988:Ethers, Cyclic / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D010616:Phenanthrenes / Q000378:metabolism*; D012867:Skin / Q000378:metabolism*; D014316:Tritium
chemical_list: D002273:Carcinogens; D002911:Chrysenes; D004852:Epoxy Compounds; D004988:Ethers, Cyclic; D010616:Phenanthrenes; D014316:Tritium; D004247:DNA; C008422:5-methylchrysene