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This Article Full Text Full Text (PDF) All Versions of this Article: 295/1/G7    most recent 00606.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Talukder, J. R. Articles by Sundaram, U. PubMed PubMed Citation Articles by Talukder, J. R. Articles by Sundaram, U.

TRANSLATIONAL PHYSIOLOGY

Identification and characterization of rabbit small intestinal villus cell brush border membrane Na-glutamine cotransporter

Section of Digestive Diseases, Department of Medicine, West Virginia University, School of Medicine

Submitted 28 December 2007 ; accepted in final form 17 April 2008

ABSTRACT

Glutamine, the primary metabolic fuel for the mammalian small intestinal enterocytes, is primarily assimilated by Na-amino acid cotransporters. Although Na-solute cotransport has been shown to exist in the brush border membrane (BBM) of the absorptive villus cells, the identity of Na-glutamine cotransport in rabbit small intestinal villus cells was unknown. Na-dependent glutamine uptake is present in villus BBM vesicles. An intravesicular proton gradient did not stimulate this Na-dependent glutamine uptake, whereas Li⁺ did not significantly suppress this uptake. These observations in concert with amino acid substitution studies suggested that Na-glutamine cotransporter in the villus cell BBM was the newly identified cotransporter B⁰AT1 (SLC6A19). Quantitative real-time PCR identified the message for this cotransporter in villus cells. Thus a full-length cDNA of B⁰AT1 was cloned and expressed in MDA-MB-231 cells. This expressed cotransporter exhibited characteristics similar to those observed in villus cells from the rabbit small intestine. Antibody was generated for B⁰AT1 that demonstrated the presence of this cotransporter protein in the villus cell BBM. Kinetic studies defined the kinetic parameters of this cotransporter. Thus this study describes the identification, cloning, and characterization of the Na-amino acid cotransporter responsible for the assimilation of a critical amino acid by the absorptive villus cells in the mammalian small intestine.

regulation of intestinal absorption; Na-amino acid cotransport; epithelial transport; villus cells