Stimulation of mucosal uptake of selenium from selenite byl-cysteine in sheep small intestine
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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.
Index EntriesSelenium salts and intestinal absorption in sheep selenium salts and influence of cysteine on intestinal absorption of selenium stimulation of selenium absorption by cysteine and Na+-and pH-dependence
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