Interaction between selenium and methylmercury

The available data on the influence of selenium on the toxicity of methylmercury and of methylmercury on selenium as a nutrient and toxic agent are reviewed. Selenium as selenite has a relative protective effect on acute and subacute toxicity of methylmercury in the rat and the quail. The protective mechanism is far from clear. Of special interest is the fact that selenium-treated animals may remain unaffected, even when they have attained tissue mercury levels otherwise associated with toxic effects. Selenite causes some increase of tissue mercury levels in methylmercury-exposed animals. On the other hand, methylmercury induces a remarkable enhancement of organ concentrations of selenium in animals given selenite. The interaction between selenium and methylmercury is in many ways different from that between selenium and inorganic mercury, and also from that between selenium and other metals. Due to the considerable interspecies differences in the toxicity of methylmercury, the available data do not allow conclusions on interactions in man. Practical implications of a possible protective effect of selenium on methylmercury toxicity in humans are discussed.