Transport of thiamine in human intestine: mechanism and regulation in intestinal epithelial cell model Caco-2

• Published in: American Journal of Physiology: Cell Physiology Vol. 277; no. 4; pp. C645 - C651
• Main Authors: Said, H.M, Ortiz, A, Kumar, C.K, Chatterjee, N, Dudeja, P.K, Rubin, S
• Format: Journal Article
• Language: English
• Published: United States 01.10.1999
• Subjects: Biological Transport - physiology; Caco-2 Cells; Cations - pharmacology; cell lines; Humans; Hydrogen-Ion Concentration; intestinal mucosa; Intestinal Mucosa - cytology; Intestinal Mucosa - metabolism; Intestines - metabolism; nutrient transport; nutrient uptake; Osmolar Concentration; Protein Kinases - physiology; Sodium - metabolism; Temperature; thiamin; Thiamine - analogs & derivatives; Thiamine - antagonists & inhibitors; Thiamine - metabolism; Time Factors; uptake mechanisms
• ISSN: 0002-9513; 0363-6143; 2163-5773; 1522-1563
• DOI: 10.1152/ajpcell.1999.277.4.c645

Veterans Affairs Medical Center, Long Beach 90822; University of California Irvine, Irvine 92717; Wadsworth Veterans Affairs Medical Center and University of California Los Angeles, Los Angeles, California 90073; and Westside Veterans Affairs Medical Center and University of Illinois-Chicago, Chicago, Illinois 60612 The present study examined the intestinal uptake of thiamine (vitamin B 1 ) using the human-derived intestinal epithelial cells Caco-2 as an in vitro model system. Thiamine uptake was found to be 1 ) temperature and energy dependent and occurred with minimal metabolic alteration; 2 ) pH sensitive; 3 ) Na + independent; 4 ) saturable as a function of concentration with an apparent Michaelis-Menten constant of 3.18 ± 0.56 µM and maximal velocity of 13.37 ± 0.94 pmol · mg protein 1 · 3 min 1 ; 5 ) inhibited by the thiamine structural analogs amprolium and oxythiamine, but not by unrelated organic cations tetraethylammonium, N -methylnicotinamide, and choline; and 6 ) inhibited in a competitive manner by amiloride with an inhibition constant of 0.2 mM. The role of specific protein kinase-mediated pathways in the regulation of thiamine uptake by Caco-2 cells was also examined using specific modulators of these pathways. The results showed possible involvement of a Ca 2+ /calmodulin (CaM)-mediated pathway in the regulation of thiamine uptake. No role for protein kinase C- and protein tyrosine kinase-mediated pathways in the regulation of thiamine uptake was evident. These results demonstrate the involvement of a carrier-mediated system for thiamine uptake by Caco-2 intestinal epithelial cells. This system is Na + independent and is different from the transport systems of organic cations. Furthermore, a CaM-mediated pathway appears to play a role in regulating thiamine uptake in these cells. thiamine transport; human intestinal cells; transport mechanism; transport regulation