GENOTOXIC EFFECTS OF THE O-PHENYLPHENOL METABOLITES PHENYLHYDROQUINONE AND PHENYLBENZOQUINONE IN V79 CELLS

o-Phenylphenol (OPP) and its sodium salt, sodium o-phenylphenate are b road spectrum fungicides and disinfectants with widespread usage. Both chemicals have been reported to induce cancer in the kidney and urina ry bladder of Fischer 344 rats. Recently it has been proposed that the metabolic activation of OPP occurs via a two-step process involving t he cytochrome P450-mediated formation of phenylhydroquinone (PHQ) in t he liver and a prostaglandin H synthase-mediated oxidation of PHQ to p henylbenzoquinone (PBQ) in the urinary tract. In order to further inve stigate the metabolic activation and genotoxic effects of OPP, we have investigated the ability of PHQ and PBQ to induce micronuclei and mut ations at the HGPRT locus in a prostaglandin H synthase-containing V79 Chinese hamster lung fibroblast cell line. In arachidonic acid-supple mented V79 cells, PHQ induced a significant increase in micronuclei wh ereas no increase was observed in cells in the absence of arachidonic acid supplementation. Immunofluorescent labeling of centromeric protei ns with the CREST antibody indicated that the arachidonic acid-depende nt induction of micronuclei by PHQ was due almost entirely to micronuc lei containing whole chromosomes which had failed to segregate properl y during mitosis. The induction of micronuclei by PHQ was significantl y inhibited by treatment of the cells with indomethacin, aspirin, asco rbic acid, dithiothreitol and reduced gluthathione supporting a role f or prostaglandin H synthase in the genotoxic effects of PHQ. No increa se in 6-thioguanine-resistant cells was observed in cells treated with PHQ or PBQ. This arachidonic acid-dependent conversion of PHQ to a ge notoxic species is consistent with the hypothesis that a prostaglandin H synthase-mediated activation of PHQ may be involved in OPP- and SOP P-induced urinary tract carcinogenesis and also suggests that the indu ction of aneuploidy may play an important role in OPP-induced tumorige nesis.