NHE1, NHE2, and NHE3 contribute to regulation of intracellular pH in murine duodenal epithelial cells

J Praetorius, D Andreasen, B L Jensen, M A Ainsworth, U G Friis, T Johansen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Na(+)/H(+)-exchangers (NHE) mediate acid extrusion from duodenal epithelial cells, but the isoforms involved have not previously been determined. Thus we investigated 1) the contribution of Na(+)-dependent processes to acid extrusion, 2) sensitivity to Na(+)/H(+) exchange inhibitors, and 3) molecular expression of NHE isoforms. By fluorescence spectroscopy the recovery of intracellular pH (pH(i)) was measured on suspensions of isolated acidified murine duodenal epithelial cells loaded with 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Expression of NHE isoforms was studied by RT-PCR and Western blot analysis. Reduction of extracellular Na(+) concentration ([Na(+)](o)) during pH(i) recovery decreased H(+) efflux to minimally 12.5% of control with a relatively high apparent Michaelis constant for extracellular Na(+). The Na(+)/H(+) exchange inhibitors ethylisopropylamiloride and amiloride inhibited H(+) efflux maximally by 57 and 80%, respectively. NHE1, NHE2, and NHE3 were expressed at the mRNA level (RT-PCR) as well as at the protein level (Western blot analysis). On the basis of the effects of low [Na(+)](o) and inhibitors we propose that acid extrusion in duodenal epithelial cells involves Na(+)/H(+) exchange by isoforms NHE1, NHE2, and NHE3.
Original languageEnglish
JournalAmerican Journal of Physiology: Gastrointestinal and Liver Physiology
Volume278
Issue number2
Pages (from-to)G197-206
ISSN0193-1857
Publication statusPublished - 2000

Keywords

  • Amiloride
  • Ammonia
  • Animals
  • Blotting, Western
  • Duodenum
  • Epithelial Cells
  • Extracellular Space
  • Homeostasis
  • Hydrogen-Ion Concentration
  • Kinetics
  • Mice
  • Mice, Inbred C57BL
  • Quaternary Ammonium Compounds
  • RNA, Messenger
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sodium
  • Sodium-Hydrogen Antiporter
  • Spectrometry, Fluorescence

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