Immunohistochemical studies on the ontogenesis of some endocrine cells in the chicken antrum and duodenum

The time of appearance, morphology and topographic distribution of gastrin/CCK-, somatostatin-, 5HT-, and bombesin-like immunoreactive cells during embryonic and postnatal development were studied in chicken antrum and duodenum with immunohistochemical methods. Gastrin/CCK-like cells appeared on or about the 11th day in the antrum and duodenum, somatostatin-like cells around the 12th day in the antrum and the 11th day in the duodenum, bombesin-like cells appeared only in the antrum and only at hatching. In the early stages of development all the immunoreactive cells were localized in the surface epithelium, descending deeper into the glands as these form, although some cells could always be seen in the surface epithelium. Around the 17th day the number of gastrin/CCK-like cells and somatostatin-like cells in the antrum increases, while 5HT-like already become more numerous in the duodenum from the 13th day onwards. Two territories were recognized in the antrum of the adult: the first was near the duodenum where gastrin/CCK-like and somatostatin-like cells, often in close contact, were very numerous; the other territory was near the gizzard where bombesin-like cells were more numerous. Both regions contained 5HT-like cells in smaller number. In adult duodenum, 5HT-like cells were the most numerous, while somatostatin-like cells and gastrin/CCK-like cells, found in more superficial locations, were more scanty.