Histological and immunocytochemical data on the differentiation of intestinal endocrine cells in human fetus

The differentiation of the argyrophil, argentaffin, 5-hydroxytryptamine (5-HT)-, somatostatin (SOM)-, cholecystokinin (CCK)-, substance P (SP)-, methionine-enkephalin (Met-Enk)- and vasoactive intestinal polypeptide (VIP)-immunoreactive entero-endocrine cells (EECs) was examined in human fetuses. A great increase in the frequency of EECs in the duodenum and the rectum was observed between the 7th and 12th gestation week. The differentiation of the EECs advanced distally in the small intestine and proximally in the large intestine. In 24-25-week-old fetuses the frequency of the EECs was also increased in the ileum and the colon. A different time-course of the appearance and differentiation of the types of EECs was observed. Met-Enk- and VIP-immunoreactive endocrine cells were not detected at any age. A regional difference in the frequency and morphology of the endocrine cell types was observed in the eldest fetuses.