Do enterochromaffin (EC) cells contain motilin?

Identity of motilin-immunoreactive cells (motilin cells) and enterochromaffin (EC) cells was investigated. Human and dog gastro-entero-pancreatic tissues were examined using conventional stain technologies, indirect immunofluorescence and immunoperoxidase methods and electron microscopy. Enterochromaffin cells were identified by Masson-Hamperl's silver impregnation method. Results obtained were summarized as follows. 1. Motilin-immunoreactive cells were dispersed in the epithelium of the small intestine with a vague tendency to be concentrated in the deeper portion of the crypt. They were most frequent in the duodenal and jejunal mucosa; a few of them were also seen in the ileal mucosa. No motilin cells were found in the stomach, colon, rectum and pancreas. 2. In contrast, enterochromaffin cells were found in the stomach and pancreas as well as in the whole intestine. 3. Observation of the same or adjacent sections after immunofluorescence and argentaffin reaction demonstrated that motilin-reactive cells were non-argentaffin. Different techniques, including immunoperoxidase method at the electron microscope level, indicated that the enterochromaffin cells were totally different from the cells which contained motilin. 4. In the human fetus (16 to 24-week-old), Segi's cap, i.e., aggregated basal-granulated cells on the top of the villus discovered by Segi (1935), was seen in the duodenum and upper jejunum. The majority of basal-granulated cells forming this body were argyrophil, 30-50% of them were argentaffin (i.e., enterochromaffin), and less than 10% of them were motilin-immunoreactive.