Neuro-epithelial bodies in organ cultures of fetal rabbit lungs. Ultrastructural characteristics and effects of drugs.

Lung explants from fetal rabbit at the late glandular stage of development (20 days' gestation) and near term (31 days' gestation) were maintained in organ culture for up to 22 days. They were studied by light and electron microscopy to determine whether neuro-epithelial bodies (NEB) of the lung retain structural integrity in vitro. Cultured NEB retained argyrophilia and specific amine fluorescence after formaldehyde condensation. Their ultrastructural morphology showed some differences from that of uncultured NEB: the terminal axons had degenerated and the secretory granules (dense-core vesicles, DCV) were slightly larger, more pleomorphic, more electron-dense, and redistributed throughout the cytoplasm rather than being confined chiefly to the basal regions. These changes, together with hypertrophy of Golgi zones, suggest increased synthesis and storage of secretory products in the DCV during culture. In NEB from near-term explants cultured for 7 days and incubated with reserpine, the core of DCV decreased in size and electron-density and became finely granular, a sign of amine release. Ca++ ionophore No. A-23187, also, induced changes in the ultrastructure of DCV, suggesting that the secretory process in lung neuro-endocrine cells, as in other secretory cells, is Ca++-dependent.