Increase of lung sodium-potassium-ATPase activity during recovery from high-permeability pulmonary edema

Previous studies have suggested that recovery from pulmonary edema may be dependent on active sodium ion transport. Most of the data supporting this concept came from work done in isolated type II cells, isolated lung preparations, or in models of alveolar flooding. There is a limited amount of information regarding the role of active sodium ion transport in vivo. Furthermore, most of this information was obtained in one model of pulmonary edema, the hyperoxic lung injury model. The purpose of these experiments was then to measure the activity of the sodium-potassium-adenosinetriphosphatase (Na+-K+-ATPase), the active component of the sodium transport process and an indirect marker of active sodium transport, during recovery from thiourea-induced pulmonary edema in rats. Na+-K+-ATPase activity was significantly increased during recovery from lung edema. This increase could not be accounted for by the Na+-K+-ATPase activity present in inflammatory cells recruited in the lung by the injury process or by a direct impact of thiourea on the enzyme. Alveolar flooding, induced by instillation of a protein-containing solution into the airways of ventilated rats also increased the activity of Na+-K+-ATPase, suggesting that activation of the enzyme is probably secondary to either the presence of edema or the physiological consequences associated with edema. The quantity of lung Na+-K+-ATPase protein was also elevated during edema resolution, indicating that augmented synthesis of this enzyme underlies the increased enzyme activity observed. The quantity of Na+-K+-ATPase protein in alveolar type II cells was also significantly enhanced during recovery from edema, suggesting that these cells contribute to active sodium transport in vivo. The results of this study suggest that active sodium transport could participate in the resolution of pulmonary edema.