Comparative evaluation of the genotoxic properties of potassium bromate and potassium superoxide in V79 Chinese hamster cells

The genotoxic potential of two oxidizing compounds, potassium bromate and p otassium superoxide, was comparatively tested in various genotoxicity tests with V79 Chinese hamster cells. Both substances clearly induced cytotoxici ty, chromosome aberrations and increased DNA migration in the alkaline come t assay. Using a modified comet assay protocol with FPG protein, a DNA repa ir enzyme which specifically nicks DNA at sites of 8-oxoguanines and formam idopyrimidines, we detected oxidative DNA base damage only after potassium bromate treatment. HPLC analysis also revealed significantly increased leve ls of 8-oxodeoxyguanosine after potassium bromate treatment but not after p otassium superoxide treatment. Furthermore, potassium bromate clearly induc ed gene mutations at the HPRT locus while potassium superoxide only had a s mall effect on HPRT mutant frequencies, Molecular analysis of potassium bro mate-induced mutations indicated a high portion of deletion mutations. Thre e out of four point mutations were G to T transversions which typically ari se after replication of 8-oxoguanine. Our results suggest that the two oxid izing compounds induce specific patterns of genotoxic effects that reflect the types of DNA alterations induced by different reactive oxygen species ( ROS). (C) 1999 Elsevier Science B.V. All Fights reserved.