Transepithelial glycylsarcosine transport in intestinal Caco-2 cells mediated by expression of H(+)-coupled carriers at both apical and basal membranes

• Published in: The Journal of biological chemistry 1993-04, Vol.268 (11), p.7640-7642
• Main Authors: THWAITES, D. T, BROWN, C. D. A, HIRST, B. H, SIMMONS, N. L
• Format: Article
• Language: English
• Subjects: Adenocarcinoma; Analysis of Variance; Biological and medical sciences; Biological Transport; Carrier Proteins - metabolism; Cell Membrane - metabolism; Cell physiology; Colonic Neoplasms; Dipeptides - metabolism; Epithelium - metabolism; Fluoresceins; Fluorescent Dyes; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Kinetics; Mannitol - metabolism; Membrane and intracellular transports; Molecular and cellular biology; Tumor Cells, Cultured
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(18)53004-0

Glycylsarcosine (Gly-Sar) transport in human intestinal epithelial (Caco-2) cells has been investigated. Gly-Sar transport, from apical to basal surfaces (Ja-b), and intracellular accumulation are greatest when the apical medium is acidified (apical pH 6.0, basal pH 7.4). Both transport and accumulation are susceptible to saturation and competition. Similarly, Gly-Sar transport, from basal to apical surfaces (Jb-a), is increased with acidification of the basal medium (basal pH 6.0, apical pH 7.4). Apical addition of 20 mM Gly-Sar (pH 6.0) to Caco-2 cell monolayers loaded with the pH indicator BCECF (2',7'-bis(2-carboxyethyl)-5-(6)-carboxyfluorescein) caused a marked cytosolic acidification. Basolateral application of 20 mM Gly-Sar (pH 6.0) also caused a fall in intracellular pH. These observations are consistent with the expression of H(+)-coupled dipeptide transporters at both membrane faces of the human intestinal epithelial Caco-2 cell line. We also provide direct evidence for dipeptide-stimulated H(+)-influx, across both apical and basolateral membranes, in this intact epithelial cell system.