Hypoxia reduces airway epithelial sodium transport in rats

Ascent to high altitude leads to pulmonary edema formation in some individu als. Recent laboratory evidence supports the hypothesis that hypoxia may im pair the function of the alveolar epithelium and thus augment edema accumul ation via reduced clearance of lung liquid. We investigated the effect of h ypobaric hypoxia on epithelial sodium transport in adult Sprague-Dawley rat s by measuring the nasal transepithelial potential difference (PD) as an in dex of airway sodium transport. Baseline PDs were similar to those previous ly reported in other species. Administration of amiloride resulted in a sig nificant fall in nasal PD, as did ouabain administration for 24 h (-27.8 vs . -18.8 mV; P = 0.001; n = 5 rats). Exposure to hypobaric hypoxia (0.5 atm) for 24 h caused a significant fall in nasal PD (-23.7 vs. -18.8 mV; P = 0. 002; n = 15 rats), which was not additive to the changes in nasal. PD produ ced by amiloride or ouabain. We conclude that subacute exposure to moderate hypobaric hypoxia can inhibit sodium transport by the airway epithelium in rats.