Endocrine-like cells of the pulmonary epithelium of the human adult lung.

The morphological and histochemical characteristics of endocrine-like cells of the pulmonary epithelium of the right lower lobe of 12 human adult lungs were studied. Few cells were reactive to the argyrophil silver method of Grimelius and of Sevier and Munger and cells with a similar morphology and distribution emitted a green or yellow fluorescence after treatment of the lung epithelium with the amine presursors L-DOPA or L-HTP, respectively. A greater number of cells seems to be demonstrated by electron microscopy. The cells were characterized by small, round secretory granules showing a central dense core and a very thin clear halo between the core and the surrounding membrane. The cells are thought to be related to the endocrine-like cells of the pulmonary epithelium of the human foetal lung and to cells of carcinoids of larger bronchi.