Pulmonary response to atmospheric pollutants. 3. The role of pulmonary collapse in the induction of aberrations of the type 2 pneumocyte.

Type 2 pneumocyte responses were studied in the rat after experimental right apical lobe collapse induced by surgical occlusion of the apical bronchus. After initial degranulation, type 2 pneumocytes underwent proliferation, and exhibited large numbers of well formed and densely staining intracytoplasmic surfactant lamellar bodies. The proliferative response, which was diffuse in the initial 3 to 25 days, became focal by 50 days and thereafter subsided. These results are discussed in relationship to the responses of the type 2 pneumocyte to toxic injury as previously reported.