Enteroendocrine cells in the digestive tract of Barbus conchonius (teleostei, cyprinidae).

Just as in other cyprinids, three zones can be distinguished in the digestive tract of Barbus conchonius. A fat absorptive zone (65--75%), including the intestinal bulb, is followed by a protein absorptive zone (25--35%) and a small ion and water absorptive zone (less than 5%). The main characteristics of these zones are described. Four types of enteroendocrine cells can be distinguished between the intestinal epithelial cells. The number decreases in the caudal direction, and there are very few in the protein absorptive zone. All the enteroendocrine cells are argyrophilic and differ mainly in the size and shape of their secretory granules. Serotonin producing and hence argentaffin cells have not been found. Amine precursor uptake and decarboxylation (APUD) by the enteroendocrine cells of adult fishes has not been observed. The possible functions of the enteroendocrine cells are discussed. (Auto-)phagosomes, common in epithelial cells of the gut of B. conchonius, show similar staining characteristics as the enteroendocrine cells; their function is discussed.