O Schröder1, J Opritz, J Stein. 1. Division of Gastroenterology, 2nd Department of Internal Medicine, Johann Wolfgang Goethe University, Frankfurt, Germany.
Abstract
BACKGROUND/AIMS: There is substantial evidence that transcellular flux of short-chain fatty acid (SCFA) absorption, at least in part, is mediated by an anion exchange process with bicarbonate. METHODS: This anion exchange system was further characterized in apical membrane vesicles of the rat distal colon by studying substrate and inhibitor specificities of a variety of substituted monocarboxylic acids as well as of known inhibitors of the recently described monocarboxylate transporter MCT1 and MCT2. RESULTS: SCFA transport was significantly reduced in the presence of branched and unbranched SCFAs and several bromo, chloro and mercapto analogues as well as nicotinic acid and L-lactate. In contrast, known inhibitors of monocarboxylate transporter proteins like stilbene derivatives, phloretin and 2-cyano-4-hydroxycinnamate did not inhibit bicarbonate-gradient stimulated butyrate transport. Kinetic analysis of increasing substrate concentrations of 3-mercaptopropionate, L-lactate and nicotinic acid showed saturation kinetics with apparent K(i) of 6.1, 18.3 and 14.7 mmol/l, respectively. CONCLUSIONS: The data not only confirm earlier results that absorption of SCFAs in apical membranes of the rat distal colon is mediated by a relatively low affinity/high capacity SCFA(-)/HCO(-)(3) exchange mechanism, but also indicate that although this anion transporter shares some functional similarities, is not identical with the recently cloned MCT isoforms. Copyright 2000 S. Karger AG, Basel.
BACKGROUND/AIMS: There is substantial evidence that transcellular flux of short-chain fatty acid (SCFA) absorption, at least in part, is mediated by an anion exchange process with bicarbonate. METHODS: This anion exchange system was further characterized in apical membrane vesicles of the rat distal colon by studying substrate and inhibitor specificities of a variety of substituted monocarboxylic acids as well as of known inhibitors of the recently described monocarboxylate transporter MCT1 and MCT2. RESULTS:SCFA transport was significantly reduced in the presence of branched and unbranched SCFAs and several bromo, chloro and mercapto analogues as well as nicotinic acid and L-lactate. In contrast, known inhibitors of monocarboxylate transporter proteins like stilbene derivatives, phloretin and 2-cyano-4-hydroxycinnamate did not inhibit bicarbonate-gradient stimulated butyrate transport. Kinetic analysis of increasing substrate concentrations of 3-mercaptopropionate, L-lactate and nicotinic acid showed saturation kinetics with apparent K(i) of 6.1, 18.3 and 14.7 mmol/l, respectively. CONCLUSIONS: The data not only confirm earlier results that absorption of SCFAs in apical membranes of the rat distal colon is mediated by a relatively low affinity/high capacity SCFA(-)/HCO(-)(3) exchange mechanism, but also indicate that although this anion transporter shares some functional similarities, is not identical with the recently cloned MCT isoforms. Copyright 2000 S. Karger AG, Basel.
Authors: Aze Wilson; Wendy A Teft; Bridget L Morse; Yun-Hee Choi; Sarah Woolsey; Marianne K DeGorter; Robert A Hegele; Rommel G Tirona; Richard B Kim Journal: Dig Dis Sci Date: 2015-07-10 Impact factor: 3.199
Authors: Ming-Shan Kao; Yanhan Wang; Shinta Marito; Stephen Huang; Wan-Zhen Lin; Jon A Gangoiti; Bruce A Barshop; Choi Hyun; Woan-Ruah Lee; James A Sanford; Richard L Gallo; Yuping Ran; Wan-Tzu Chen; Chun-Jen Huang; Ming-Fa Hsieh; Chun-Ming Huang Journal: J Microb Biochem Technol Date: 2016-06-19