title: H(+)-coupled (Na(+)-independent) proline transport in human intestinal (Caco-2) epithelial cell monolayers.
abstract: 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 Isc 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.
authors.affiliation: Department of Physiological Sciences, University of Newcastle upon Tyne, Medical School, UK.
authors.forename: D T
authors.initials: DT
authors.lastname: Thwaites
authors.forename: G T
authors.initials: GT
authors.lastname: McEwan
authors.forename: M J
authors.initials: MJ
authors.lastname: Cook
authors.forename: B H
authors.initials: BH
authors.lastname: Hirst
authors.forename: N L
authors.initials: NL
authors.lastname: Simmons
mesh_terms: D001692:Biological Transport; D002460:Cell Line; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D011522:Protons; D012964:Sodium / Q000378:metabolism
chemical_list: D011522:Protons; D011392:Proline; D012964:Sodium