Speciation of Dimethylarsinous Acid and Trimethylarsine Oxide in Urine from Rats Fed with Dimethylarsinic Acid and Dimercaptopropane Sulfonate

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Abstract
Speciation of arsenic in urine from rats treated with dimethylarsinic acid (DMAV) alone or in combination with dimercaptopropane sulfonate (DMPS) were studied. Methods were developed for the determination of the methylarsenic metabolites, especially trace levels of dimethylarsinous acid (DMAIII) and trimethylarsine oxide (TMAO), in the presence of a large excess of DMAV. Success was achieved by using improved ion-exchange chromatographic separation combined with hydride generation atomic fluorescence detection. Micromolar concentrations of DMAIII were detected in urine of rats fed with a diet supplemented with either 100 μg/g of DMAV or a mixture of 100 μg/g of DMAV and 5600 μg/g of DMPS. No significant difference in the DMAIII concentration was observed between the two groups; however, there was a significant difference in TMAO concentrations. Urine from rats fed with the diet supplemented with DMAV alone contained 73 ± 30 μM TMAO, whereas urine from rats fed with the diet supplemented with both DMAV and DMPS contained only 2.8 ± 1.4 μM TMAO. Solutions containing mixtures of 100 μg/L DMAV or TMAO and 5600 μg/L DMPS did not show reduction of DMAV and TMAO. The significant decrease (p < 0.001) of the TMAO concentration in rats administered with both DMAV and DMPS suggests that DMPS inhibits the biomethylation of arsenic.

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