Ultrastructural identification of a new cell type--the N-cell as the source of neurotensin in the gut mucosa.

The neurotensin-cell is identified immunohistochemically and ultrastructurally by differential counting of endocrine cells in the gut of a primate (Tupaia belangeri). Utilizing light microscopy, the EC-cells are identified by the Masson-Fontana silver stain; with the same method the neurotensin cells are not stained. The other endocrine cells have been quantified in the small intestine using the peroxidase-antiperoxidase stain with antisera against glucagon, somatostatin, cholecystokinin, gastrin, secretin, pancreatic polypeptide, gastric inhibitory peptide and neurotensin. In the ileal mucosa of Tupaia, the most frequent endocrine cell is the EC-cell followed by the glucagonoid cell, (L-cell). The immunoreactive neurotensin cell represents the third most frequent endocrine cell in this region. On the ultrastructural level, this third most frequent endocrine cell is a heretofore undescribed cell, the N-cell, containing electron dense secretory granules measuring 335 +/- 87 nm in diameter.