Regulation of the apical Cl-/HCO-3 exchanger pendrin in rat cortical collecting duct in metabolic acidosis

Am J Physiol Renal Physiol. 2003 Jan;284(1):F103-12. doi: 10.1152/ajprenal.00205.2002. Epub 2002 Aug 13.


Pendrin is an apical Cl(-)/OH(-)/HCO(3)(-) exchanger in beta-intercalated cells (beta-ICs) of rat and mouse cortical collecting duct (CCD). However, little is known about its regulation in acid-base disorders. Here, we examined the regulation of pendrin in metabolic acidosis, a condition known to decrease HCO(3)(-) secretion in CCD. Rats were subjected to NH(4)Cl loading for 4 days, which resulted in metabolic acidosis. Apical Cl(-)/HCO(3)(-) exchanger activity in beta-ICs was determined as amplitude and rate of intracellular pH change when Cl was removed in isolated, microperfused CCDs. Intracellular pH was measured by single-cell digital ratiometric imaging using fluorescent pH-sensitive dye 2',7'-bis-(3-carboxypropyl)-5-(and-6)-carboxyfluorescein-AM. Pendrin mRNA expression in kidney cortex was examined by Northern blot hybridizations. Expression of pendrin protein was assessed by indirect immunofluorescence. Microperfused CCDs isolated from acidotic rats demonstrated approximately 60% reduction in apical Cl(-)/HCO(3)(-) exchanger activity in beta-ICs (P < 0.001 vs. control). Northern blot hybridizations indicated that the mRNA expression of pendrin in kidney cortex decreased by 68% in acidotic animals (P < 0.02 vs. control). Immunofluorescence labeling demonstrated significant reduction in pendrin expression in CCDs of acidotic rats. We conclude that metabolic acidosis decreases the activity of the apical Cl(-)/HCO(3)(-) exchanger in beta-ICs of the rat CCD by reducing the expression of pendrin. Adaptive downregulation of pendrin in metabolic acidosis indicates the important role of this exchanger in acid-base regulation in the CCD.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acid-Base Equilibrium / physiology
  • Acidosis / metabolism*
  • Amino Acid Sequence
  • Ammonium Chloride / pharmacology
  • Animals
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism*
  • Chloride-Bicarbonate Antiporters / genetics*
  • Chloride-Bicarbonate Antiporters / metabolism*
  • Diuretics / pharmacology
  • Female
  • Fluorescent Antibody Technique
  • Gene Expression / physiology
  • Kidney Cortex / metabolism
  • Kidney Tubules, Collecting / metabolism*
  • Membrane Transport Proteins*
  • Molecular Sequence Data
  • RNA, Messenger / analysis
  • Rats
  • Rats, Sprague-Dawley
  • Sulfate Transporters


  • Carrier Proteins
  • Chloride-Bicarbonate Antiporters
  • Diuretics
  • Membrane Transport Proteins
  • RNA, Messenger
  • SLC26A4 protein, human
  • Sulfate Transporters
  • Ammonium Chloride