title: Regulation of the expression of the Cl-/anion exchanger pendrin in mouse kidney by acid-base status.
abstract: BACKGROUND
  Pendrin belongs to a superfamily of Cl-/anion exchangers and is expressed in the inner ear, the thyroid gland, and the kidney. In humans, mutations in pendrin cause Pendred syndrome characterized by sensorineural deafness and goiter. Recently pendrin has been localized to the apical side of non-type A intercalated cells of the cortical collecting duct, and reduced bicarbonate secretion was demonstrated in a pendrin knockout mouse model. To investigate a possible role of pendrin in modulating acid-base transport in the cortical collecting duct, we examined the regulation of expression of pendrin by acid-base status in mouse kidney.
  
  
  METHODS
  Mice were treated orally either with an acid or bicarbonate load (0.28 mol/L NH4Cl or NaHCO3) or received a K+-deficient diet for one week. Immunohistochemistry and Western blotting was performed.
  
  
  RESULTS
  Acid-loading caused a reduction in pendrin protein expression levels within one day and decreased expression to 23% of control levels after one week. Concomitantly, pendrin protein was shifted from the apical membrane to the cytosol, and the relative abundance of pendrin positive cells declined. Similarly, in chronic K+-depletion, known to elicit a metabolic alkalosis, pendrin protein levels decreased and pendrin expression was shifted to an intracellular pool with the relative number of pendrin positive cells reduced. In contrast, following oral bicarbonate loading pendrin was found exclusively in the apical membrane and the relative number of pendrin positive cells increased.
  
  
  CONCLUSIONS
  These results are in agreement with a potential role of pendrin in bicarbonate secretion and regulation of acid-base transport in the cortical collecting duct.
authors.affiliation: Department of Cellular and Molecular Physiology, Yale University, School of Medicine, New Haven, Connecticut, USA. wagnerca@physiol.unizh.ch
authors.forename: Carsten A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Karin E
authors.initials: KE
authors.lastname: Finberg
authors.forename: Paul A
authors.initials: PA
authors.lastname: Stehberger
authors.forename: Richard P
authors.initials: RP
authors.lastname: Lifton
authors.forename: Gerhard H
authors.initials: GH
authors.lastname: Giebisch
authors.forename: Peter S
authors.initials: PS
authors.lastname: Aronson
authors.forename: John P
authors.initials: JP
authors.lastname: Geibel
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000471:Alkalosis / Q000139:chemically induced / Q000378:metabolism; D000818:Animals; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000032:analysis / Q000096:biosynthesis; D002352:Carrier Proteins / Q000032:analysis / Q000096:biosynthesis*; D016764:Cell Polarity; D003600:Cytosol / Q000378:metabolism; D007672:Kidney Cortex / Q000166:cytology / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D017419:Potassium, Dietary / Q000494:pharmacology; D017693:Sodium Bicarbonate / Q000494:pharmacology; D000076988:Sulfate Transporters
chemical_list: C496024:Aqp2 protein, mouse; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D017419:Potassium, Dietary; C085609:SLC26A4 protein, human; D000076988:Sulfate Transporters; D017693:Sodium Bicarbonate