Immunohistochemical, morphometric, and ultrastructural investigations of the early development of insulin, somatostatin, glucagon, and PP cells in foetal human pancreas.

Fresh autopsy specimens of pancreas, taken from 18 human foetuses at the 10th (n = 4), 12th (n = 7), and 14th (n = 7) weeks of gestation, were analyzed immunohistochemically for the presence of islet parenchymal cells, immunoreactive with antisera raised against insulin (B cells), somatostatin (D cells), glucagon (A cells), and pancreatic polypeptide (PP cells). All four islet cell types were found sporadically within or near the epithelium of the small excretory ducts at the 10th week of development. At the 12th week, their presence appeared to be no longer restricted to the duct epithelium, as some B cells were found also in small clusters outside the ducts. At the 14th week of development, the B cells formed large clusters in the neighborhood of the excretory ducts. It is at this stage that the first parenchymal cells with Grimelius argyrophilia could be found. They were supposed to represent A cells. The B cells were found to be the predominating type of islet cells (about 50%) at the 10th week of gestation. The relative volume density was about 25% for the D cells, about 15% for the A cells, and about 10% for the PP cells. At the 12th and 14th weeks of development, the relative numbers of B and PP cells decreased somewhat (to 36 and 6%, respectively), whereas those of the D and A cells were found to increase (to 30 and 27%, respectively). The relative volume density of the total islet parenchyma was about 2, 6, and 21% at the 10th, 12th, and 14th weeks of development, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)