title: Mutagenicity and cytotoxicity of benzo(a)pyrene benzo-ring epoxides.
abstract: Four benzo-ring epoxides of the environmental carcinogen benzo(a)pyrene (BP) were tested for mutagenic and cytotoxic activity in 3 strains of Salmonella typhimurium (TA1538, TA98, and TA100) and in Chinese hamster V79 cells. Although very unstable in aqueous solution, 7beta,8alpha-dihydroxy-0beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (diol epoxide 1), with the 7-hydroxyl group on the same face of the molecule as the epoxide oxygen, was 1.5 to 4 times as mutagenic in the bacterial strains as was its more stable stereoisomer 7beta,8alpha-dihydroxy-9alpha,10beta-epoxy-7,8,9.10-tetrahydrobenzo(a)pyrene (diol epoxide 2). In V79 cells, diol epoxide 1 had one-third the mutagenic activity of diol epoxide 2 but was at least 10 times more labile than diol epoxide 2 in the tissue culture medium. The half-life of diol epoxide 1 in tissue culture medium was about 30 sec, whereas the half-life of diol epoxide 2 was between 6 and 12 min. 9,10-Epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene, which is saturated in the benzo ring, is also very unstable and has mutagenic activity equal to or greater than diol epoxide 1 in the bacterial and mammalian cells. 7,8-Epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene was more stable in aqueous solution than any of the 9,10-epoxides of BP but was much less mutagenic in both the bacterial and mammalian cells. In v79 cells, diol epoxides 1 and 2 and 9,10-opoxy-7,8,9,10-tetrahydrobenzo(a)pyrene were more than 40 times more cytotoxic than 7,8-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene. The mutagenicity of the 2 tetrahydro epoxides toward strain TA98 of S. typhimurium was readily abolished by purified epoxide hydrase, whereas the mutagenic activity of the 2 diol epoxides was relatively unaffected by coincubation with the enzyme.
mesh_terms: D000818:Animals; D001580:Benzopyrenes / Q000378:metabolism / Q000633:toxicity*; D001966:Bromine / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D055598:Chemical Phenomena; D002621:Chemistry; D006224:Cricetinae; D004851:Epoxide Hydrolases / Q000494:pharmacology; D004852:Epoxy Compounds / Q000633:toxicity*; D004988:Ethers, Cyclic / Q000633:toxicity*; D006207:Half-Life; D009153:Mutagens; D010641:Phenotype; D011409:Propylene Glycols / Q000633:toxicity; D012486:Salmonella typhimurium / Q000187:drug effects*; D013045:Species Specificity; D014297:Trimethylsilyl Compounds / Q000633:toxicity; D014867:Water
chemical_list: D001580:Benzopyrenes; D004852:Epoxy Compounds; D004988:Ethers, Cyclic; D009153:Mutagens; D011409:Propylene Glycols; D014297:Trimethylsilyl Compounds; D014867:Water; D004851:Epoxide Hydrolases; D001966:Bromine