Mechanisms of surfactant exocytosis in alveolar type II cells in vitro and in vivo.

Surfactant secretion must be regulated to maintain a low surface tension in the lung during various conditions such as exercise. In vitro studies reveal a slow, unique exocytotic process at the interface of stimulated and constitutive exocytosis. The exocytotic mechanisms and sites of regulation in vivo, however, are still poorly understood.