title: Mutagenesis and DNA adduct formation by 1-nitropyrene in Chinese hamster ovary cells without exogenous metabolic activation.
abstract: The direct-acting mutagenicity of 1-nitropyrene (1-NP), a tumorigenic environmental pollutant and model nitropolycyclic aromatic hydrocarbon, was studied in Chinese hamster ovary (CHO) cells. Previous reports indicated that 1-NP, a potent direct-acting mutagen in Salmonella typhimurium, was mutagenic in CHO cells only in the presence of an exogenous activation system. In this study, a DNA-repair-deficient CHO cell line, CHO-UV5, and the repair-proficient CHO-K1-BH4 cell line were used to measure the direct-acting mutagenicity of highly purified samples of 1-NP. Exposure of CHO-K1-BH4 cells for 5, 12, and 24 hr did not increase mutations at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus (p greater than 0.1; paired t test; n = 5-6), while treatment of CHO-UV5 cells for 24 hr produced a statistically significant induction of mutants (22 +/- 6 mutants per 10(6) clonable cells vs a solvent control value of 9 +/- 3 per 10(6) cells; p less than 0.01; n = 6). 32P-Postlabeling analysis of the DNA adducts formed in CHO-UV5 cells following 1-NP exposure revealed the presence of a single major adduct. Based on its chromatographic properties, its sensitivity to nuclease P1 digestion, and its resistance to hydrazine treatment, the adduct appeared to be N-(deoxyguanosin-8-yl)-1-aminopyrene, which was presumably produced by nitroreduction of 1-NP to N-hydroxy-1-aminopyrene. These results suggest that the use of extended treatment times and DNA-repair-deficient cells may be required to assess adequately the mutagenicity of nitropolycyclic aromatic hydrocarbons in CHO cells.
authors.affiliation: National Center for Toxicological Research, Jefferson, Arkansas 72079.
authors.forename: J R
authors.initials: JR
authors.lastname: Thornton-Manning
authors.forename: B A
authors.initials: BA
authors.lastname: Smith
authors.forename: F A
authors.initials: FA
authors.lastname: Beland
authors.forename: R H
authors.initials: RH
authors.lastname: Heflich
mesh_terms: D000818:Animals; D001345:Autoradiography; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000187:drug effects*; D004260:DNA Repair / Q000187:drug effects*; D005260:Female; D016296:Mutagenesis / Q000187:drug effects*; D010053:Ovary / Q000187:drug effects / Q000378:metabolism; D011721:Pyrenes / Q000633:toxicity*
chemical_list: D011721:Pyrenes; D004247:DNA; C032668:1-nitropyrene