EVALUATION OF THE GENOTOXIC PROPERTIES OF PARAQUAT IN V79 CHINESE-HAMSTER CELLS

The genotoxic potential of the herbicide paraquat (PQ), an intracellul ar generator of superoxide, was comparatively tested in various genoto xicity tests with V79 Chinese hamster cells. PQ clearly induced cytoto xicity and chromosome aberrations but did not induce gene mutations at the HPRT locus or increased DNA migration in the comet assay under th e same treatment conditions. Using a modified comet assay protocol wit h formamidopyrimidine-DNA glycosylase (FPG) protein, a DNA repair enzy me which specifically nicks DNA at sites of 8-oxo-guanines and formami dopyrimidines, we could not detect oxidative DNA base damage after PQ treatment. When cells were treated directly on the slides after lysis (i.e., after the cell membrane barrier was eliminated), increased DNA migration was observed after treatment with high PQ-concentrations Our results suggest that PQ does not significantly induce DNA lesions rel evant for HPRT gene mutations in cultivated V79 cells. Since PQ-induce d chromosome aberrations only occur after treatment with high concentr ations which totally prevent cell survival and are not preceded by an induction of DNA strand breakage in intact cells, their biological sig nificance has to be questioned. (C) 1998 Elsevier Science B.V.