Studies of the cellular physiology of various lung cells will be pursued. These studies involve both normal lung cells and the changes associated with hypoxia and with oxidant injury. The approaches include: Measurements of redox ratios of NAD ion/NADH and NADP ion/NADPH. Measurements of the activities of key energy metabolism enzymes and related metabolic variables. Studies of transport mechanisms of water, cations and macromolecular chemical species. The implantation of "de novo" enzyme activity. Therapeutic trials in animals of possible agents directed against pulmonary O2 toxicity. Alterations in intracellular and subcellular pH produced by oxidant injury. Modifications of lung cell function by oxidant injury. BIBLIOGRAPHIC REFERENCES: Intracellular Edema and Dehydration: Effects on Energy Metabolism in Alveolar Macrophages, N. Lewiston, J. Theodore, E.D. Robin, Science, Jan., 1976. Platypnea Related to Orthodeoxia Caused by True Vascular Lung Shunts, E.D. Robin, D. Laman, B.R. Horn, J. Theodore, (Accepted for publication by the N. Eng. J. of Med., 1976).