title: Human cell-mediated benzo(a)pyrene cytotoxicity and mutagenicity in human diploid fibroblasts.
abstract: A human epithelial cell-mediated cytotoxicity and mutagenicity assay system for benzo(a)pyrene [B(a)P] has been developed with human fibroblasts as the target cells. Lethally X-irradiated human kidney carcinoma-derived epithelial cells, which had constant levels of B(a)P-metabolizing activity, were cocultivated with target human skin fibroblasts (XP12BE), which lack excision repair capability for B(a)P-DNA adducts. The optimal conditions determined for the cell-mediated cytotoxicity assay were a 48-hr exposure to B(a)P concentrations ranging from 0.1 to 1 microM at a metabolizing cell:target cell ratio of at least 1:1. Under these conditions, the frequency of mutations to 6-thioguanine resistance induced in the target XP12BE cells by B(a)P as well as the binding of tritium-labeled B(a)P to DNA was also shown to be concentration dependent. High-pressure liquid chromatography analysis of enzymatically degraded B(a)P-DNA adducts revealed two peaks: a major peak (82%) which cochromatographed with the guanosine adduct-standard synthesized from anti-isomeric-7,8-dihydrodiol-9,10-epoxide of B(a)P; and a minor peak (18%) which cochromatographed with the guanosine adduct-standard synthesized from syn-isomeric-7,8-diol-9,10-epoxide of B(a)P. Human liver carcinoma- and lung carcinoma-derived cell lines, capable of metabolizing B(a)P, proved equal to or better than the kidney carcinoma-derived cell line in producing cytotoxic B(a)P metabolites in the cell-mediated cytotoxicity assay with target XP12BE cells.
mesh_terms: D001564:Benzo(a)pyrene; D001580:Benzopyrenes / Q000378:metabolism* / Q000633:toxicity; D001711:Biotransformation; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D009152:Mutagenicity Tests / Q000379:methods; D009374:Neoplasms, Experimental / Q000378:metabolism*; D014983:Xeroderma Pigmentosum / Q000235:genetics
chemical_list: D001580:Benzopyrenes; D001564:Benzo(a)pyrene