Selenium detoxification by methylation

The major detoxification process for selenium is methylation. The major pathway for the formation of methylated compounds in biological systems is transmethylation catalyzed by methyltransferases. In this study methyltransferase activity was assayed in the liver cytosol prepared from different strains of rats using HPLC method by measuring the formation of epinephrine from norepinephrine. The methyltransferase activity in Fischer, Wistar, and Sprague-Dawley rats were 1.65 x 10(-12), 0.74 x 10(-12), and 1.2 x 10(-12) moles epinephrine formed/mg protein/hr respectively. Volatilization of injected Se (2.5 mg/kg, i.p.) was found to be higher in Wistar rats compared to Fischer rats. LD50 for Wistar and Fischer rats were 2.58 and 3.15 mg Se/kg respectively. Our results suggest that the methylation of dimethyl selenide to trimethhyl selenide appears to be an important step in the detoxification of selenium.