Affiliation:
1. Department of Medicine, University of Illinois at Chicago and Westside Veterans Administration Medical Center, Chicago, Illinois 60612
Abstract
Current studies were undertaken to characterize the mechanism of short-chain fatty acid (SCFA) transport in isolated human proximal colonic basolateral membrane vesicles (BLMV) utilizing a rapid-filtration n-[14C]butyrate uptake technique. Human colonic tissues were obtained from mucosal scrapings from organ donor proximal colons. Our results, consistent with the existence of a HCO[Formula: see text]/SCFA exchanger in these membranes, are summarized as follows: 1) n-[14C]butyrate influx was significantly stimulated into the vesicles in the presence of an outwardly directed HCO[Formula: see text] and an inwardly directed pH gradient; 2) n-[14C]butyrate uptake was markedly inhibited (∼40%) by anion exchange inhibitor niflumic acid (1 mM), but SITS and DIDS (5 mM) had no effect; 3) structural analogs e.g., acetate and propionate, significantly inhibited uptake of HCO[Formula: see text] and pH-gradient-driven n-[14C]butyrate; 4) n-[14C]butyrate uptake was saturable with a Kmfor butyrate of 17.5 ± 4.5 mM and a Vmaxof 20.9 ± 1.2 nmol · mg protein−1· 5 s−1; 5) n-[14C]butyrate influx into the vesicles demonstrated a transstimulation phenomenon; and 6) intravesicular or extravesicular Cl−did not alter the anion-stimulated n-[14C]butyrate uptake. Our results indicate the presence of a carrier-mediated HCO[Formula: see text]/SCFA exchanger on the human colonic basolateral membrane, which appears to be distinct from the previously described anion exchangers in the membranes of colonic epithelia.
Publisher
American Physiological Society
Subject
Physiology (medical),Gastroenterology,Hepatology,Physiology
Cited by
36 articles.
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