The Journal of Membrane Biology

, Volume 211, Issue 3, pp 139–150 | Cite as

Mechanisms of Acid and Base Secretion by the Airway Epithelium

  • Horst Fischer
  • Jonathan H. Widdicombe
Topical Review


One of the main functions of the airway epithelium is to inactivate and remove infectious particles from inhaled air and thereby prevent infection of the distal lung. This function is achieved by mucociliary and cough clearance and by antimicrobial factors present in the airway surface liquid (ASL). There are indications that airway defenses are affected by the pH of the ASL and historically, acidification of the airway surfaces has been suggested as a measure of airway disease. However, even in health, the ASL is slightly acidic, and this acidity might be part of normal airway defense. Only recently research has focused on the mechanisms responsible for acid and base secretion into the ASL. Advances resulted from research into the airway disease associated with cystic fibrosis (CF) after it was found that the CFTR Cl channel conducts HCO 3 and, therefore, may contribute to ASL pH. However, the acidity of the ASL indicated parallel mechanisms for H+ secretion. Recent investigations identified several H+ transporters in the apical membrane of the airway epithelium. These include H+ channels and ATP-driven H+ pumps, including a non-gastric isoform of the H+-K+ ATPase and a vacuolar-type H+ ATPase. Current knowledge of acid and base transporters and their potential roles in airway mucosal pH regulation is reviewed here.


Apical Membrane Airway Epithelium Paracellular Pathway Airway Surface Liquid Cystic Fibrosis Airway 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



Many thanks to Sarah Inglis (Dundee, Scotland), Mauri Krouse (Stanford, California), and Terry Machen (Berkeley, California) for reading and commenting on the manuscript. The authors’ laboratories are supported by NIH HL071829.


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© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  1. 1.Children’s Hospital Oakland Research InstituteOaklandUSA
  2. 2.University of CaliforniaDavisUSA

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