title: Mediating role of metabolic activation in in vitro cytotoxicity assays.
abstract: Enzymatic activation of polycyclic aromatic hydrocarbons (PAHs) and its effect on cytotoxicity were studied using the neutral red viability assay as the end point. Benzo[a]pyrene was progressively cytotoxic to human hepatoma (HepG2) cells over a 1- to 3-d period, and after induction of monooxygenase activity with a polychlorobiphenyl (PCB) mixture (Arochlor 1254), cytotoxicity was increased about threefold. Concomitant with Arochlor exposure was an increase in the activity of 7-ethoxycoumarin odeethylase, which could be inhibited by exposure to alpha-naphthoflavone. Human keratinocytes (NHEK), but not fibroblasts (HFF), were sensitive to the cytotoxicity of benzo[a]pyrene. However, preexposure of the keratinocytes to Arochlor did not increase their sensitivity to benzo[a]pyrene. Neither the keratinocytes, fibroblasts, nor HepG2 cells were sensitive to acenaphthene. Addition of hamster or rat hepatic S9 mix, however, resulted in toxicity from benzo[a]pyrene and acenaphthene. 7,12-Dimethylbenz[a]anthracene was only mildly cytotoxic to the fibroblasts, and its cytotoxicity was not enhanced in the presence of rat or hamster S9 mix. Exposure of the HepG2 cells to 7,12-dimethylbenz[a]anthracene showed progressive toxicity over a 1- to 3-d period. Prior exposure of the HepG2 cells to Arochlor did not enhance their sensitivity to 7,12-dimethylbenz[a]anthracene. Human keratinocytes were sensitive to 7,12-dimethylbenz[a]anthracene, with cytotoxicity markedly increasing over a 1- to 3-d period.
authors.affiliation: Laboratory Animal Research Center, Rockefeller University, New York, New York 10021.
authors.forename: H
authors.initials: H
authors.lastname: Babich
authors.forename: N
authors.initials: N
authors.lastname: Martin-Alguacil
authors.forename: E
authors.initials: E
authors.lastname: Borenfreund
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism / Q000633:toxicity; D001189:Aryl Hydrocarbon Hydroxylases / Q000032:analysis; D001564:Benzo(a)pyrene / Q000378:metabolism / Q000633:toxicity; D001711:Biotransformation; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D006801:Humans; D014116:Toxicology / Q000379:methods*
chemical_list: D001564:Benzo(a)pyrene; D015127:9,10-Dimethyl-1,2-benzanthracene; D001189:Aryl Hydrocarbon Hydroxylases