Figure 1

The distal airway epithelium contains alveolar type I and type II cells and Clara cells, which possess various pumps and channels that achieve clearance of edema fluid. Sodium is transported through channels on the apical membrane and extruded from the cell by the Na⁺/K⁺-ATPase located on the basolateral membrane. This transport generates a sodium gradient that drives the transport of water, which is accomplished in part through water channels. AQP, aquaporin; CFTR, cystic fibrosis transmembrane conductance regulator; CNG, cyclic nucleotide-gated; ENaC, epithelial Na⁺channel. From Matthay and coworkers [3], with permission from the American Physiological Society.