Examination of in vivo mutagenicity of sodium arsenite and dimethylarsinic acid in gpt delta rats.

Arsenic is a well-known human bladder and liver carcinogen, but its exact mechanism of carcinogenicity is not fully understood. Dimethylarsinic acid (DMA) is a major urinary metabolite of sodium arsenite (iAs) and induces urinary bladder cancers in rats. DMA and iAs are negative in in vitro mutagenicity tests. However, their in vivo mutagenicities have not been determined. The purpose of present study is to evaluate the in vivo mutagenicities of DMA and iAs in rat urinary bladder epithelium and liver using gpt delta F344 rats. Ten-week old male gpt delta F344 rats were randomized into 3 groups and administered 0, 92mg/L DMA, or 87mg/L iAs (each 50mg/L As) for 13weeks in the drinking water. In the mutation assay, point mutations are detected in the gpt gene by 6-thioguanine selection (gpt assay) and deletion mutations are identified in the red/gam genes by Spi selection (Spi assay). Results of the gpt and Spi assays showed that DMA and iAs had no effects on the mutant frequencies or mutation spectrum in urinary bladder epithelium or liver. These findings indicate that DMA and iAs are not mutagenic in urinary bladder epithelium or liver in rats.