EFFECTS OF SIMULTANEOUS LOW-LEVEL DIETARY SUPPLEMENTATION WITH INORGANIC AND ORGANIC SELENIUM ON WHOLE-BODY, BLOOD, AND ORGAN LEVELS OF TOXIC METALS IN MICE

Classical experiments have demonstrated that Se compounds protect against the toxicity of several toxic metals in acute experiments with simultaneous parenteral administration of high doses of Se and the toxic metal. Blood and organ levels of the toxic metals were increased, conceivably due to formation of inert Se complexes. Less is known about effects of long-term Se status on the toxicokinetics of toxic metals. Possible Se interactions in toxic metal biokinetics should therefore be studied at Se levels ranging from those just sufficient to avoid Se deficiency and up to those believed to be optimum in relation to antioxidative acid other beneficial effects of Se. The toxic-metal exposure levels investigated should be similar to those occuring in human populations that are not occupationally exposed. To study interactions between Se and toxic metals at ultralow exposure levels, mice were fed semisynthetic diets containing different levels of Se. The mice were given ultralow doses of metal salts either as a single oral dose by stomach tube or as prolonged exposure in the drinking water. Diets with high or normal Se levels slightly, but nonsignificantly increased the whore-body retention (WBR) of Hg++ and CH3Hg+ compared to a diet low in Se. The dietary Se level was, however, without effect on the WBR of Cd2+ and Ag2+ in single-dose experiments. During prolonged exposure, the diets fortified with Se increased the WBR of Ag2+, had no effect on WBR of Hg2+, and reduced the WBR of CH3Hg+ and Cd2+. During prolonged exposure, the diets fortified with Se reduced blood Hg++ while organ levels were unaltered. Blood and organ levels of CH3Hg+ were reduced or unaltered. Diets with added Se reduced blood and organ levels of Cd++ but increased brood and organ levels of Ag++. The blood lead level was reduced by Se supplementation. These results are in contrast to those previously published for Se effects on the toxicokinetics of Cd and Hg compounds. The results indicate, that Se supplementation might be beneficial in populations exposed for extended periods to increased environmental levels of certain toxic metals, e.g., Cd, Hg and CH3Hg.