Abstract
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.
Highlights
Newcastle upon TyneNE2 4HH, United Kingdom we have utilized the human intestinal Caco-2 epithelial cell line reconstituted as epithelial monolayers on permeable fil
From experiments with brush-border membrane vesicles (BBMV), that dipeptideuptake across the intestinal apical membrane is both electrogenic and enhanced by an inwardly-directed pH gradient(Ganapathyand Leibach, 1985).direct H+ coupling or intravesicular accumulation have not been convincingly demonstrated in mammalian intestine
Our results indicate the presence of a functional dipeptide carrier in the apical membrane of Caco-2 cells, and are in agreement with observations of cephalosporin uptake (Dantzig and Bergin, 1990) andtransport(Inui et aL, 1992)
Summary
Newcastle upon TyneNE2 4HH, United Kingdom we have utilized the human intestinal Caco-2 epithelial cell line reconstituted as epithelial monolayers on permeable fil-. We provide direct evidence for dipeptide-stimulated H+-influx, across both apical and basolateral membranes, in this intact epithelial cell system. Fluxes across the monolayers into the contralateral chamber are expressed as pmol/cm*.h. At the end of the incubation period cell monolayers were washed in 4 X 500-ml volumes of Krebs buffer (pH 7.4) to remove any loosely associated radiolabel, and removed from the insert.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
