Ultrastructural changes in the synthetic and secretory patterns of pulmonary surfactant following pilocarpine in vivo

Previous studies have demonstrated that the muscarinic agonist pilocarpine stimulates the secretion of pulmonary surfactant from mammalian alveolar type II cells. The results of the present study quantify, via ultrastructural stereologic analysis, this response through 24 hours. The cytoplasmic volume density of lamellar bodies decreases significantly at 0.5 and 4 hours postinjection. This value is increased significantly at 12 hours post-injection. Elements of the secretory apparatus increase significantly at many of the post-injection times. At 12 hours post-injection many of the type II cells are quite laden with lamellar bodies, with some appearing surprisingly large. This may be a useful model for continued study of the relationship between synthesis and secretion of pulmonary surfactant.