The Use of Transmission Electron Microscopy to Characterize Differentiated Rat Lung Cells Cultured in Vitro

Abstract

Pulmonary surfactant stabilizes alveolar volumes by lowering surface tension at the alveolar fluid-air interface. Its formation has been correlated with the presence of osmiophilic lamellar bodies in the cytoplasm of type II alveolar pneumonocytes. Inadequate surfactant production is considered responsible for respiratory distress syndrome or hyaline membrane disease in premature infants. Biochemical studies of the synthesis, storage, and secretion of surfactant are made difficult by the heterogeneity of cells in intact lung. This paper describes the use of transmission electron microscopy as a tool for the morphological characterization of type II pneumonocytes in an in vitro model system for studying synthesis, storage, and secretion of pulmonary surfactant.Lungs from fetal rats at 19 days gestation are removed, minced, washed and then dissociated at 37°C in an enzymatic solution containing 0.1% trypsin, 0.1% collagenase and 1% chicken serum in calcium-magnesium-free saline.