Transepithelial glycylsarcosine transport in intestinal Caco-2 cells mediated by expression of H(+)-coupled carriers at both apical and basal membranes.
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.
Thwaites
D T
DT
Department of Physiological Sciences, University of Newcastle upon Tyne Medical School, United Kingdom.
Brown
C D
CD
Hirst
B H
BH
Simmons
N L
NL
D000230:Adenocarcinoma; D000704:Analysis of Variance; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003110:Colonic Neoplasms; D004151:Dipeptides / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008353:Mannitol / Q000378:metabolism; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D004151:Dipeptides; D005452:Fluoresceins; D005456:Fluorescent Dyes; C004194:glycylsarcosine; D008353:Mannitol; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein