Luminal Osmolarity Downregulates Gene Expression of Na+/H+ Exchanger (NHE3) in Rat Colon Mucosa

Marc A. Doble, Vicky B. Tola, Robert R. Cima, Michael J. Zinner, Michael A. Klein, David I. Soybel

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Water-coupled Na+ absorption in the colon is mediated principally by Na+/H+ exchange (isoforms NHE2 and NHE3). To determine whether luminal ion composition or osmolarity influences NHE expression in colon mucosa, two groups (n = 6 in each) of adult male Sprague-Dawley rats underwent sham laparotomy or loop ileostomy. In these studies, diversion did not markedly alter mRNA levels for NTHE2, NHE3, or Na+/K+, at 8 or 21 days, indicating that loss of luminal volume does not alter NHE gene expression. To evaluate the effects of specific luminal components, we infused equal volumes of half-normal (154 mOsm) or iso-osmolar (308 mOsm) solutions of saline and mannitol into the diverted colon. All solutions elicited significant (45% to 60%; P <0.05) decreases in mRNA levels for NHE3, with iso-osmolar mannitol eliciting the greatest changes. Decreases in NHE2 and Na+/K+ mRNA levels were observed following these infusions but were not as marked as the changes for NHE3. These findings suggest that (1) loss of luminal Na+ is not, in itself, a signal that regulates NHE expression and (2) infusion of any solute, including Na+ itself, provides a signal to downregulate expression of NHE3 in colon mucosa.

Original languageEnglish (US)
Pages (from-to)531-535
Number of pages5
JournalJournal of Gastrointestinal Surgery
Issue number5
StatePublished - 2000
Externally publishedYes


  • Colon mucosa
  • Ileostomy
  • Ion transport
  • Na/H exchanger
  • Osmolarity

ASJC Scopus subject areas

  • Surgery
  • Gastroenterology


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