Epithelial Sodium Channel Function in Health and Disease in the Adult Lung

For gas exchange to occur, the epithelium of the lung must maintain a humidified atmosphere with only a thin layer of fluid lining the airway surface. Absorption of fluid out of the airway and alveolar lumen requires active transport of sodium ions (Naþ) from the apical surface of the pulmonary epithelium, across the apical and basolateral membranes of epithelial cells, and into the interstitial space and=or bloodstream. Pharmacological inhibitors and genetic manipulations that disrupt Naþ transport result in fluid accumulation within the lung and failure of gas exchange. The importance of Naþ transport in the lung is also demonstrated in several human disease processes, where abnormal absorption of Naþ contributes to the pathophysiology of pulmonary disease.