W. Olivera

Role of the Na,K-ATPase α2 subunit in lung liquid clearance

An important function of alveolar epithelial cells is to keep the airspace free of liquid and preserve gas exchange. Previous studies have suggested that Na,K-ATPase may play a role contributing to alveolar epithelial vectorial sodium transport and thus lung liquid clearance1-3. In the lungs the αl and β 1 isoforms have been localized to alveolar type 2 (AT2) cells 4,5. The α2 isoform has been described in whole lung homogenates from adult rats6,7. The normal lung has two types of alveolar epithelial cells. Alveolar type 2 cells (AT2) are cuboidal cells that occupy about 5% of the alveolar surface area, and synthesize and secrete pulmonary surfactant 8. Alveolar type 1 cells (ATI) are large flattened cells that cover >90% of the alveolar surface and are thought to be terminally differentiated8. Expression of Na,K-ATPase αl, α2 and βl subunits was investigated in rat AT2 cells cultured for seven days, a period during which they lose their phenotypic markers and differentiate toward an alveolar type 1-like cell phenotype.