In vivo intestinal absorption of selenate and selenite by rats.

Intestinal absorption of selenate and selenite was investigated in rats by using an in vivo perfusion technique. Different segments of the intestine were perfused with an isotonic solution containing different concentrations of SeO42- or SeO32-. The site of greatest SeO42- absorption was found to be the ileum followed in descending order by the proximal jejunum and large intestine (cecum and colon). Furthermore, SeO42- was absorbed significantly faster from the ileum than SeO32-. The concentration dependence of SeO42- absorption indicates that SeO42- is absorbed by a saturable transport mechanism of the ileal mucosa. Absorption of SeO42- at a concentration of 0.01 mM was not affected by the presence of 1 mM SeO42- in the perfusate. When the SeO42- concentration of the perfusate was increased to 1 mM, the absorptive functions of the ileal epithelium appeared to be generally impaired. It is concluded that selenate is absorbed from the ileum by a carrier-mediated mechanism.