Influence of dietary selenite on the binding characteristics of rat serum proteins to mercurial compounds

Abstract

The effect of dietary selenite on the binding characteristics of serum proteins was investigated with rats. In the control serum, the maximal binding of phenylmercuric acetate (PMA) and methylmercuric chloride (MMC) to rat serum protein was approx. 18 and 9 nmoles per mg protein, respectively. The binding of Hg2+ was biphasic and it did not reach a maximum at the concentrations used. Selenite treatment caused a reduction in binding capacity of serum proteins to Hg2+ and PMA, and an increase in the binding affinities. However, there were no such changes for the binding of MMC. Selenite protection from mercury toxicity, therefore, acts not only via a change in tissue distribution and a change in the formation of seleno-proteins but, also, via a change in the binding characteristics to some mercury compounds. In the case of methylmercury, a different mechanism of protection must exist as the modification of tissue distribution, its binding to subcellular and soluble proteins and the binding characteristics remained equivocal.