The alveolar type II cells as a model for investigating the metabolism of surfactant phospholipids.

The use of type II pneumocytes in pure culture allows the investigator to directly define at the cellular level the metabolism of pulmonary surfactant. Surfactant analysis and/or secretion has been shown to be enhanced and depressed by a variety of substances, and the main metabolic pathways of the major components have been elucidated. Type II cells are also important in maintaining the in vivo homeostasis of the pulmonary alveolus, because after lung injury they proliferate and serve as stem cells for type I cells. In view of the increasing therapeutic use of surfactant supplementation in RDS and ARDS, the regulation of surfactant secretion is of particular interest, and presumably involves a receptor mediated mechanism in which surfactant associated apoproteins seem to play a pivotal role. These findings support the view that surfactant secretion is a self regulated phenomenon.