Intestinal absorption of selenite, selenate, and selenomethionine in the rat

Abstract

Regional characteristics of intestinal absorption of selenocompounds under conditions of dietary selenium deficiency, intraluminal glutathione (GSH), and GSH depletion by buthionine [S,R] sulfoximine (BSO) treatment were studied. Absorption of 75Se from selenite, selenate, and selenomethionine (SeMet) was determined in ligated loops from duodena, jejuna, and ilea of selenium-deficient rats (0.009 ppm Se) or rats fed selenite-supplemented diets (0.20 ppm Se). Selenium deficiency had no effect on absorption of any selenocompound in any intestinal segment. SeMet was absorbed most rapidly from all segments. Selenate and selenite were most efficiently absorbed from the ileum. Substantial 75Se was retained within ileal tissue during selenite and SeMet absorption but was readily transferred to the body during ileal selenate uptake. Luminal GSH (50 μmol/L) had no effect on mucosal GSH levels nor on selenite uptake. BSO treatment decreased tissue GSH levels to 37%–54% of controls depressing 75Se-selenite uptake to 55%–64% and transfer to 29%–34% of controls. 75Se-SeMet absorption was not altered by 1 mmol/L intraluminal GSH or by mucosal GSH depletion. No evidence for homeostatic regulation of selenium absorption was obtained. Intracellular GSH appears to be involved in transepithelial transport of 75Se-selenite but not 75Se-SeMet.