Widespread distribution of bronchopulmonary endocrine cells immunoreactive for calcitonin in the lung of the normal adult rat.

The nature and distribution of bronchopulmonary endocrine cells immunoreactive for calcitonin was studied in normal adult Wistar albino rats by immunoenzyme histochemistry with the peroxidase-antiperoxidase technique. A widespread distribution of both solitary endocrine cells and neuroepithelial bodies immunoreactive for calcitonin was found. Many, but not all, were also immunoreactive for neurone specific enolase. Although both classes of cells were present in airways and parenchyma, most of the solitary cells were found in alveolar ducts and alveoli whereas most of the neuroepithelial bodies were located in bronchi and bronchioles. Bronchopulmonary endocrine cells are generally regarded as being sparse in the adult rat. It is suggested that this may be a consequence of the use of inadequate methods in attempting to identify them. So far as is known, this is the first time that calcitonin has been demonstrated by immunohistochemical methods in the lungs of rats.