Active Na+ transport by the alveolar epithelium keeps alveoli relatively dry. Hyperoxia increases epithelial permeability, resulting in pulmonary edema. We sought to determine whether active Na+ resorption from the air spaces and Na-K-ATPase activity increased in rats exposed to >95% O2 for 60 h. The permeability x surface area products for unidirectional resorption of alveolar [14C]sucrose (PS(sucrose)) and 22Na+ (PS(Na+)) were measured in isolated, perfused rat lungs immediately after hyperoxia and after 3 and 7 days of recovery in room air. At 60 h of hyperoxia, the mean PS(sucrose) and PS(Na+) increased from 6.71 ± 0.8 x 10-5 to 12.6 ± 1.6 x 10-5 cm3/s (P = 0.029) and from 23.6 ± 1.1 x 10-5 to 31.0 ± 1.6 x 10- 5 cm3/s (P < 0.008), respectively. However, the values in individual rats ranged widely from no change to nearly a fourfold increase. Subgroup analysis revealed that benzamil- or amiloride-sensitive (transcellular) PS(Na+) was significantly reduced in the exposed lungs with normal PS(sucrose) but was maintained in the lungs with high PS(sucrose). By day 3 of recovery, mean Na+ and sucrose fluxes returned to values similar to control. Na-K-ATPase membrane hydrolytic maximal velocity (V(max)) activity fell significantly immediately after hyperoxic exposure but recovered to normal values by day 3 of recovery. The Na-K-ATPase β1-subunit antigenic signal did not significantly change, whereas the α1-subunit levels increased during recovery. In summary, there was a heterogeneous response of different rats to acute hyperoxia. Hyperoxia led to complex, nonparallel changes in Na+ pump antigenic protein, hydrolytic activity, and unidirectional active Na+ resorption. Active Na+ transport was differentially affected, depending on degree of injury, but permeability and transport normalized by day 3 of recovery.
|Original language||English (US)|
|Journal||American Journal of Physiology - Lung Cellular and Molecular Physiology|
|Issue number||6 17-6|
|State||Published - 1997|
- Acute lung injury
- Pulmonary edema
- Sodium pump