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Gastroenterology. 2002 May;122(5):1322-33.

H/dipeptide absorption across the human intestinal epithelium is controlled indirectly via a functional Na/H exchanger.

Author information

  • 1Department of Physiological Sciences, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom. d.t.thwaites@ncl.ac.uk

Abstract

BACKGROUND & AIMS:

For optimal nutrient absorption to occur, the enterocyte must express a range of specialist ion-driven carrier proteins that function cooperatively in a linked and mutually dependent fashion. Thus, absorption via the human intestinal H(+)-coupled di/tripeptide transporter (hPepT1) is dependent on maintenance of the trans-apical driving force (the H(+)-electrochemical gradient) established, in part, by brush-border Na(+)/H(+) exchanger (NHE3) activity. This study aimed to examine whether physiologic regulation of NHE3 activity can limit hPepT1 capacity and, therefore, protein absorption after a meal.

METHODS:

hPepT1 and NHE3 activities were determined in intact human intestinal epithelial Caco-2 cell monolayers by measurements of [(14)C]glycylsarcosine transport and uptake, (22)Na(+)-influx, H(+)-influx, and H(+)-efflux. Expression of NHE regulatory factors was determined by reverse-transcriptase polymerase chain reaction.

RESULTS:

Optimal dipeptide transport was observed in the presence of a transapical pH gradient and extracellular Na(+). At apical pH 6.5, and only in Na(+)-containing media, protein kinase A activation (by forskolin or vasoactive intestinal peptide) or selective NHE3 inhibition (by S1611) reduced transepithelial dipeptide transport and cellular accumulation by a reduction in the capacity (without effect on affinity) of dipeptide uptake.

CONCLUSIONS:

Protein kinase A-mediated modulation of intestinal dipeptide absorption is indirect via effects on the apical Na(+)/H(+) exchanger.

PMID:
11984519
[PubMed - indexed for MEDLINE]
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