Na(+)-independent, H(+)-coupled transepithelial beta-alanine absorption by human intestinal Caco-2 cell monolayers.

摘要: beta-Alanine transport across intact human intestinal epithelial (Caco-2) cell layers has been investigated. In Na(+)-containing solutions, net absorptive flux of beta-alanine from apical-to-basal surfaces is small or absent, despite Na(+)-dependent intracellular accumulation both apical and basal surfaces. Upon acidification (apical pH 6.0, 7.5), the surface are increased. Na(+)-free conditions, a significant observed, which markedly stimulated upon (pH 6.0). Cellular but not observed in this increased by acidic 6.0) solutions. Absorptive conditions with solutions displays saturation kinetics competitive inhibition alanine glycine, valine serine. Addition 20 mM to solution monolayers loaded indicator 2‘,7‘-bis(2-carboxyethyl-5(6)-carboxyfluorescein) causes marked decrement pH. also electrogenic, concentration-dependent increase an inward short circuit current being voltage-clamped monolayers. We conclude that proton-dependent, Na(+)-independent, amino acid transporter expressed at membrane Caco-2 cells, we provide direct evidence for acid-stimulated proton influx system.