Lung liquid clearance and NA,K-ATPase during acute hyperoxia and recovery in rats

Lung liquid clearance, epithelial permeability for Na⁺, mannitol and albumin, as well as Na,K-ATPase activity in alveolar type 2 (AT2) cells were studied during the acute and the recovery phase of hyperoxic lung injury. Rats exposed to 100% oxygen for 64 h were studied at 0, 7 and 14 d after removal from the hyperoxic chamber and compared with control rats breathing room air. In the isolated-perfused, liquid-filled rat lung, the albumin flux from the perfusate into the air spaces increased immediately after the oxygen exposure (220 ± 56 mg/h) and returned to control values (28 ± 7 mg/h) after 7 and 14 d of recovery. The small solutes (Na⁺ and mannitol) flux across the alveolar epithelium normalized only after 14 d of recovery in room air. Active Na⁺ transport and lung liquid clearance were reduced by 445% immediately after oxygen exposure when compared with control values, increased by ~56% above control values after 7 d of recovery, and returned to control values after 14 d of recovery. Paralleling these changes the Na, K-ATPase activity decreased by ~41% in AT2 cells isolated from rats after 64 h of breathing 100% O₂ and increased by ~25% after the rats recovered in room air for 7 d. These results suggest that alveolar epithelial Na,K-ATPase may contribute in the recovery from the hyperoxic lung injury by participating in the clearance of lung edema.