Characteristics of L-glutamine transport during Caco-2 cell differentiation.
Glutamine is the main fuel of intestinal epithelial cells, as well as a precursor for the intense nucleotide biosynthesis which arises with the rapid turnover of enterocytes. In order to determine whether glutamine uptake may vary as a function of metabolic demand, glutamine transport across the brush-border membrane of differentiating Caco-2 cells has been investigated. The uptake of L-[(3)H]glutamine was measured between day 7 and day 21 post-seeding. Kinetic analysis with glutamine concentrations ranging from 6.25 microM to 12.8 mM revealed the involvement of high affinity Na(+)-dependent (K(t)=110 microM) and low affinity Na(+)-independent (K(t)=900 microM) transport components at day 7. Both components were partially inhibited by L-lysine in a competitive fashion, suggesting that four different systems were responsible for glutamine uptake: B(0), B(0,+), b(0,+) and L. All four systems were present during the differentiation process, with systems L and B(0) being responsible for up to 80% of glutamine uptake. Caco-2 cell differentiation was associated with a marked decrease in L-glutamine uptake, which affected both the Na(+)-dependent and the Na(+)-independent components. In contrast to glucose uptake, the development of L-glutamine uptake across the brush-border membrane of Caco-2 cells may reflect an adjustment to cell metabolic demand rather than the progressive appearance of a vectorial transport process.
Costa
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INRA, Laboratoire de Nutrition Humaine et Physiologie Intestinale, Institut National Agronomique Paris-Grignon, 16 rue Claude Bernard, 75231 Cedex 05, Paris, France.
Huneau
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Tomé
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D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells / Q000378:metabolism* / Q000648:ultrastructure; D002454:Cell Differentiation; D016922:Cellular Senescence; D004847:Epithelial Cells / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008239:Lysine / Q000494:pharmacology; D008871:Microvilli / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology
D005973:Glutamine; D012964:Sodium; D008239:Lysine