The metabolic fate of methylmercury after administration of [203Hg]-methylmercuric chloride in combination with sodium selenite was investigated in rats. Whole body autoradiography and radioassay showed that administration of selenite decreased the mercury concentration in the liver and kidney, and increased that in the brain. The rapid changes of methylmercury concentration in the tissues after selenite injection were accompanied by increase in mercury extractable with benzene at neutral pH. The maximum levels of benzene-extractable mercury in the blood, kidney and liver were attained 30 min after selenite injection and were 30, 23 and 8 percent, respectively, of the total mercury. Thin-layer chromatography showed that the benzene-extractable mercury was a complex of methylmercury with selenium, bis(methylmercuric) selenide. These findings indicate that selenite alters the distribution of methylmercury in the tissues by formation of a diffusible complex with methylmercury, bis(methylmercuric) selenide VSports手机版. .