Chronic metabolic acidosis enhances NHE-3 protein abundance and transport activity in the rat thick ascending limb by increasing NHE-3 mRNA

Kamel Laghmani, Pascale Borensztein, Patrice Ambühl, Marc Froissart, Maurice Bichara, Orson W. Moe, Robert J. Alpern, Michel Paillard

Research output: Contribution to journalArticle

82 Scopus citations

Abstract

Chronic metabolic acidosis (CMA) is associated with an adaptive increase in the bicarbonate absorptive capacity of the rat medullary thick ascending limb (MTAL). To specify whether NHE-3, the apical MTAL Na/H exchanger, is involved in this adaptation, NHE-3 mRNA was quantified by a competitive RT- PCR using an internal standard which differed from the wild-type NHE-3 mRNA by an 80-bp deletion. CMA increased NHE-3 mRNA from 0.025 ± 0.003 to 0.042 ± 0.009 amol/ng total RNA (P < 0.005). NHE-3 transport activity was measured as the initial proton flux rate calculated from the Na-dependent cell pH recovery of Na-depleted acidified MTAL cells in the presence of 50 μM HOE694 which specifically blocks NHE-1, the basolateral MTAL NHE isoform. CMA caused a 68% increase in NHE-3 transport activity (P < 0.001). In addition, CMA was associated with a 71% increase in NHE-3 protein abundance (P < 0.05) as determined by Western blot analysis on MTAL membranes using a polyclonal antiserum directed against a cytoplasmic epitope of rat NHE-3. Thus, NHE-3 adapts to CMA in the rat MTAL via an increase in the mRNA transcript that enhances NHE-3 protein abundance and transport activity.

Original languageEnglish (US)
Pages (from-to)24-30
Number of pages7
JournalJournal of Clinical Investigation
Volume99
Issue number1
DOIs
StatePublished - Jan 1 1997

Keywords

  • NHE-3
  • Na/H exchange
  • acidosis
  • kidney

ASJC Scopus subject areas

  • Medicine(all)

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