Stimulation of mucosal uptake of selenium from selenite byl-cysteine in sheep small intestine

Abstract

The influence of cysteine (Cys) on mucosal uptake of⁷⁵Se-labeled selenite in sheep midjejunum was investigated using a short-term uptake technique.l-Cys (concn.: 1.0 mmol/L) significantly stimulated uptake of Se from selenite (concn.: 10 μmol/L). The stimulatory effect ofl-Cys on mucosal uptake of Se from selenite was Na⁺—and pH-dependent. In the absence of Na⁺, or at an acidic pH (5.0), the stimulatory effect ofl-Cys was abolished.l-alanine andl-lysine, but notl-glutamic acid inhibited uptake of Se from selenite in the presence ofl-Cys. Preincubation of mucosal preparations with 10 mmol/Ll-Cys produced enhanced mucosal uptake of Se from selenite. It is concluded from these results thatl-Cys stimulates absorption of Se from selenite probably by generation of selenodicysteine and maybe cysteine selenopersulfide that are subsequently transported across the intestinal brush border membrane by Na⁺-dependent amino acid carriers. Furthermore, intracellular generation of selenodicysteine might contribute to the uptake of Se from selenite by maintaining the concentration gradient for diffusive uptake of selenite.