Selective uptake of selenite by red blood cells

Both organic and inorganic forms of selenium (Se) can be utilized in the body, and the biotransformation of selenite into an organic form of Se in the bloodstream is the first step for the utilization of inorganic Se. Selenite injected intravenously into rats was shown to be taken up rapidly and selectively by red blood cells (RBCs) through the anion-exchange carrier. The uptake of selenite by RBCs was inhibited by 4,4'-diisothiocyano-2,2'-stilbene disulfonate, a specific inhibitor of the anion-exchange carrier (band 3 protein). The uptake was also inhibited by chromate owing to the glutathione deprivation in RBCs, which was confirmed by the inhibition by azodicarboxylic acid bis(dimethylamide). The presence of hydrogencarbonate in the incubation solution slightly retarded the uptake of selenite by RBCs. Although Se effluxed into the plasma was bound selectively to albumin, plasma proteins (albumin) did not accelerate the uptake process. Based on these results, the rapid and selective uptake of selenite by RBCs was explained by the selective and efficient uptake through the anion-exchange carrier, followed by reduction by glutathione.