Inorganic pentavalent arsenic methylation by rats: effect of concentration and dichromate

The effect of the administered arsenic (As) dose and the dichromate ion (Cr) on the methylation process of arsenic was studied in rats exposed to arsenate to elucidate the biotransformation of As. After oral administration of different As (V) and Cr (VI) concentrations, the different As metabolites (inorganic, methylarsonic acid [MMA] and dimethylarsinic acid [DMA] were separated by cation-exchange chromatography and measured by atomic absorption spectrophotometry. Administration of high doses of As produced enzymatic saturation and non-enzymatic depletion, with decreases in DMA levels. The presence of the dichromate ion supported arsenate methylation as it favored reduction of As (V) to As (III), but Cr (VI) produced a significant decrease in the total As excreted.