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 agai nst the toxicity of several toxic metals in acute experiments with sim ultaneous parenteral administration of high doses of Se and the toxic metal. Blood and organ levels of the toxic metals were increased, conc eivably due to formation of inert Se complexes. Less is known about ef fects of long-term Se status on the toxicokinetics of toxic metals. Po ssible Se interactions in toxic metal biokinetics should therefore be studied at Se levels ranging from those just sufficient to avoid Se de ficiency and up to those believed to be optimum in relation to antioxi dative acid other beneficial effects of Se. The toxic-metal exposure l evels investigated should be similar to those occuring in human popula tions that are not occupationally exposed. To study interactions betwe en Se and toxic metals at ultralow exposure levels, mice were fed semi synthetic 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 Cd2and Ag2+ in single-dose experiments. During prolonged exposure, the di ets 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 expo sure, the diets fortified with Se reduced blood Hg++ while organ level s were unaltered. Blood and organ levels of CH3Hg+ were reduced or una ltered. Diets with added Se reduced blood and organ levels of Cd++ but increased brood and organ levels of Ag++. The blood lead level was re duced by Se supplementation. These results are in contrast to those pr eviously published for Se effects on the toxicokinetics of Cd and Hg c ompounds. The results indicate, that Se supplementation might be benef icial in populations exposed for extended periods to increased environ mental levels of certain toxic metals, e.g., Cd, Hg and CH3Hg.