Mechanism of n-butyrate uptake in the human proximal colonic basolateral membranes

• Published in: American journal of physiology: Gastrointestinal and liver physiology Vol. 282; no. 4; pp. G676 - G682
• Main Authors: Tyagi, S, Venugopalakrishnan, J, Ramaswamy, K, Dudeja, P K
• Format: Journal Article
• Language: English
• Published: United States 01.04.2002
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid - pharmacology; Acetates - pharmacology; Adult; Amiloride - pharmacology; Anions; Bicarbonates - metabolism; Bicarbonates - pharmacology; Biological Transport - drug effects; Butyrates - metabolism; Carbon Radioisotopes; Cell Membrane - metabolism; Chlorides - administration & dosage; Chlorides - pharmacology; Colon - metabolism; Humans; Hydrogen-Ion Concentration; Intestinal Mucosa - metabolism; Kinetics; Membrane Potentials; Niflumic Acid - pharmacology; Propionates - pharmacology
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.00173.2000

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-[(14)C]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(3)(-)/SCFA exchanger in these membranes, are summarized as follows: 1) n-[(14)C]butyrate influx was significantly stimulated into the vesicles in the presence of an outwardly directed HCO(3)(-) and an inwardly directed pH gradient; 2) n-[(14)C]butyrate uptake was markedly inhibited (approximately 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(3)(-) and pH-gradient-driven n-[(14)C]butyrate; 4) n-[(14)C]butyrate uptake was saturable with a K(m) for butyrate of 17.5 +/- 4.5 mM and a V(max) of 20.9 +/- 1.2 nmol x mg protein(-1) x 5 s(-1); 5) n-[(14)C]butyrate influx into the vesicles demonstrated a transstimulation phenomenon; and 6) intravesicular or extravesicular Cl(-) did not alter the anion-stimulated n-[(14)C]butyrate uptake. Our results indicate the presence of a carrier-mediated HCO(3)(-)/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.