The major detoxification process for selenium is methylation. The majo
r pathway for the formation of methylated compounds in biological syst
ems 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 form
ation of epinephrine from norepinephrine. The methyltransferase activi
ty 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 fou
nd to be higher in Wistar rats compared to Fischer rats. LD(50) for Wi
star and Fischer rats were 2.58 and 3.15 mg Se/kg respectively. Our re
sults suggest that the methylation of dimethyl selenide to trimethyl s
elenide appears to be an important step in the detoxification of selen
ium.