H(+)-coupled (Na(+)-independent) proline transport in human intestinal (Caco-2) epithelial cell monolayers

D T Thwaites, Gordon T.A. McEwan, M J Cook, B H Hirst, N L Simmons

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54 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)78-82
Number of pages5
JournalFEBS Letters
Issue number1-2
Publication statusPublished - 25 Oct 1993


  • Biological Transport
  • Cell Line
  • Epithelial Cells
  • Epithelium
  • Humans
  • Hydrogen-Ion Concentration
  • Intestinal Mucosa
  • Proline
  • Protons
  • Sodium


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