Selenium is an essential trace element and supposed to play many biological roles. It is possible that protective effect of selenium on toxicities of heavy metals such as mercury and cadmium is one of the important biological roles of this essential element. It has been observed that behavior of mercuric mercury in animals is markedly affected by administration of selenium compounds and its toxicity dramatically decreased. The possible mechanism of the interaction between selenium and mercuric mercury in animals is summarized in this review. Toxicity of methylmercury is also protected by selenium, but the mechanism has not yet been clarified. Role of glutathione peroxidase, acceleration of methylmercury degradation and formation of bis (methylmercuric) selenide, are discussed as possible mechanisms of the modification of methylmercury toxicity by selenium.
