The purpose of this research project is to test whether administration of the proline analogue cis-hydroxyproline prevents acute lung injury in animal models. Proline analogues substitute for the amino acids proline and hydroxyproline in collagen, impair folding into the native triple helical structure, and thereby prevent deposition of collagen fibers in tissue. Our preliminary observations suggest that administration of cis-hydroxyproline to the rat oxygen-toxicity model protects against several of the derangements. We propose to confirm this observation and test the effect of the analogue on another model, bleomycin-induced lung injury in hamsters. We will also determine at what point in the process analogues must be administered to afford protection, and we will determine the minimum dose required for protection. Evaluation of lung chemistry will be by assays for hydroxyproline (as an index of collagen), total protein, and DNA. Physiologic analysis of pressure-volume curves of saline-filled lungs, morphometric analysis of alveolar size, number of alveoli per lung, and lung internal surface area, and histologic appraisal of the degree of fibrosis will be performed.