Abstract
The ontogeny of the six main types of gastroenteropancreatic (GEP) endocrine cells was immunohistochemically studied in developing mouse and pig. Glucagon-immunoreactive cells first appeared in the duodenum and the primordial pancreas in 9-day-old mouse and 0.8 cm (18-day-old) porcine fetuses. In the mouse pancreas, following the appearance of the glucagon-immunoreactive cells, pancreatic polypeptide (PP)-, insulin-, gastrin/cholecystokinin (gastrin/CCK)- and somatostatin-immunoreactive cells were detected in 10-, 11-, 13- and 15- day-old fetuses. In the porcine pancreas, insulin-, somatostatin- and 5-hydroxytryptamine (5-HT)-immunoreactive cells were demonstrated in 1.0 cm (20-day-old) fetuses, while PP-immunoreactive cells were observed in 2.5 cm (30-day-old) fetuses. In contrast, in the mouse gastrointestinal tract, PP- and gastrin/CCK-immunoreactive cells were first found in 14-day-old fetuses, then 5-HT- and somatostatin-immunoreactive cells in 15- and 16-day-old fetused, respectively. In the porcine gut, four kinds of immunoreactive cells appeared in 2.0-3.0 cm (28-32 day-old) fetuses. It was demonstrated that insulin-immunoreactive cells were rarely seen in the porcine antrum and duodenum in the initial stage of development. These results indicate that the glucagon-immunoreactive cells first appear in the GEP endocrine system and that the endocrine cells in the primordial pancreas appear prior to those in the digestive tract proper. Therefore, it is suggested that the ontogenic patterns of GEP endocrine cells are basically similar in mice and pigs.
