The Functional Morphology of the Pulmonary Neuroendocrine Cells in the Lung of Larval and Adult Rana ridibunda

The distribution and functional morphology of neuroendocrine cells (PNECs) were studied in the lung of tadpole and adult Rana ridibunda. The responses of PNECs to different experimental conditions were investigated in adult frog lungs. In tadpole lungs, bombesin- and somatostatin immunoreactive (IR) PNECs were found in the inner-lining epithelium. In adult frogs kept in cold water (+ 4 oC), mostly serotonin- and bombesin-IR cells had stored secretory material as well as serotonin-IR cells with released secretion, while somatostatin-IR cells with limited secretory material were scarce. In the dry aquarium, somatostatin-IR cells of adult frogs were at various secretory stages. In conclusion, the activities of PNECs varied by depending on the amount of pulmonary contribution of lungs into respiration.