Increased expression of pulmonary surfactant proteins in oxygen-exposed rats.

Exposure of adult rats to 85% ambient oxygen increased the content of surfactant proteins SP-A, SP-B, and SP-C recovered from alveolar lavage. The surfactant proteins increased during 1 to 7 d of oxygen exposure. The increased surfactant protein was associated with increased relative abundance of mRNA encoding each of the proteins in lung tissue. Exposure to hyperoxia progressively increased the amounts of the surfactant proteins in alveolar lavage fluid as estimated by immunoblot analysis after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The mRNAs encoding SP-A (1.7 and 1.0 kb), SP-B (1.6 kb), and SP-C (0.9 kb) increased significantly after oxygen exposure for 5 d. The present findings support the concept that oxygen exposure mediates surfactant protein expression at a pretranslational level.