An Immunofluorescent Study of Insulin‐, Glucagon‐, Pancreatic Polypeptide‐ and Somatostatin‐containing Cells in the Early Ovine Fetal Pancreas

Abstract

SUMMARYUsing antisera to insulin, glucagon, pancreatic polypeptide (PP) and somatostatin, the localization and cellular distribution of the four hormones were investigated in the sheep fetal pancreas of day 40-45 gestation by immunofluorescence. All four hormones were immunolocalized at this early gestational period. The endocrine cell types had a characteristic distribution and were present in different numbers. Insulin and glucagon immunoreactive cells were seen in larger numbers compared to fetal PP and somatostatin cells and were located either in the developing islets or as single scattered cells in the epithelium of the embryonic ductules. These cells became more confined to the developing islets at later stages of gestation. In the pancreas of day 40-45 fetuses PP cells were less numerous than glucagon and insulin cells while somatostatin cells were seen rarely. However, PP and somatostatin cells became more numerous at later stages of gestation. Our studies demonstrate the presence of insulin, glucagon, PP and somatostatin within distinct cell types in the early sheep fetal pancreas.

Diminished β-cell replication contributes to reduced β-cell mass in fetal sheep with intrauterine growth restriction

“…Quantification of these extra-islet ␤-cells showed that they account for ϳ10% of the population in the control pancreas and for only 8% of the IUGR ␤-cell population, a significant reduction. These cells may represent new endocrine cell formation or even small islets (9,44,57), but it has been shown that the percentage of individual endocrine cells declines after midgestation in the sheep as they form small and large endocrine clusters (44,62). Although reduction in this nonislet ␤-cell population contributes to the overall reduction in whole pancreatic ␤-cell mass, we show that a similar reduction of 52% occurs in the ␤-cell fraction localized to the small islets in the IUGR pancreas.…”

Adaptation of ovine fetal pancreatic insulin secretion to chronic hypoglycaemia and euglycaemic correction

“…Similarly, in fetal sheep, the pancreatic responsiveness to glucose increases almost fourfold over the last half of gestation (Aldoretta et al 1998). In vivo responsiveness of the ovine fetal pancreas correlates very closely with the presence of islet structures and increasing pancreas insulin content during the final third of gestation (Willes et al 1969;Reddy et al 1988). These developmental changes resemble human pancreatic development during the last trimester (Falin, 1967;Hellerstrom et al 1992).…”

Pancreatic islet plasticity: Interspecies comparison of islet architecture and composition

“…Fetal endocrine cell development and islet formation has been studied in domestic sheep ( Ovis aries ) 70. The β-cells are present as both clusters (i.e., islets) and as single cells near ducts from 60–80 days gestation.…”