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H + ‐coupled (Na + ‐independent) proline transport in human intestinal (Caco‐2) epithelial cell monolayers
Author(s) -
Thwaites David T.,
McEwan Gordon T.A.,
Cook Martin J.,
Hirst Barry H.,
Simmons Nicholas L.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80378-8
Subject(s) - proline , caco 2 , symporter , apical membrane , chemistry , enterocyte , monolayer , biophysics , absorption (acoustics) , membrane transport , intracellular , biochemistry , transporter , membrane , cell , amino acid , small intestine , biology , materials science , gene , composite material
Previously, absorption of l ‐proline across the apical membrane of the intestinal enterocyte has been attributed to transport via the Na + ‐dependent Imino system. However, net (absorptive) transport of proline across intact Caco‐2 cell monolayers was enhanced by acidification of the apical environment, under both Na + ‐containing and Na + ‐free conditions. This Na + ‐independent pH‐dependent proline flux was associated with H + flow across the apical membrane as determined by continuous measurement of intracellular pH. H + /proline symport was associated with an inward I sc in voltage‐clamped Caco‐2 epithelial layers demonstrating the electrogenic nature of this transport process. In conclusion Caco‐2 cells possess an apically‐localised, Na + ‐independent, electrogenic H + /imino acid transporter which may play an important role in intestinal proline absorption.