Stereologic analysis of rat type II alveolar cells in vitro.

When type II alveolar cells are maintained in culture, they gradually lose their characteristic lamellar bodies and their ability to secrete surface active material. We evaluated the feasibility of using electron microscopy and stereology to quantitate the effects of multiple culture conditions on the ultrastructure of type II alveolar cells, in vitro. The decrease in lamellar body volume density with time in culture was not affected by culturing the cells in the presence of insulin, fibronectin, or complex extracellular matrix. However, dexamethasone significantly prevented this decrease in lamellar body volume density. The mitochondrial volume density of the cells remained constant with time in culture under control conditions and in the presence of insulin, dexamethasone, or fibronectin. There was, however, a significant increase in mitochondrial volume density, for a short period of time (48 hours), when cells were cultured in the presence of complex extracellular matrix. These studies suggest that electron microscopy with stereology provides an excellent technique to quantitate in vitro ultrastructural changes in cultured type II alveolar cells.