Pancreatic islet cell hormones. Distribution of cell types in the islet and evidence for the presence of somatostatin and gastrin within the D cell

Abstract

This paper is a review of investigations on the identification and distribution of the islet cells responsible for the production of somatostatin and gastrin in the pancreas of rat and man. The controversy as to whether D cells contain somatostatin or gastrin is clarified by immunocytochemical evidence presented, which demonstrates that gastrin and somatostatin positive cells are present as 2 distinct cell populations in the pyloric mucosa of rat and man, whereas the somatostatin containing D cell of the human pancreatic islet is also the same cell which stains immunocytochemically for gastrin. In the human islet the β cells are arranged in cord like clusters (due to invaginations of the islet periphery) which often give the islet a multilobular appearance in histologic sections. The α cells (glucagon), D cells (somatostatin and gastrin) and occasional human pancreatic polypeptide cell(s) are usually distributed around the periphery of the more centrally located β cells in the larger islets. This distribution is readily apparent after multiple immunocytochemical staining of the same islet for both insulin and glucagon. Cells in the human islet, therefore, are not randomly arranged as previously reported, but instead are organized in a definite pattern similar to that seen in rats. The evidence for the interrelations of islet cells is consistent with the distribution of islet cell types recognized by tinctorial staining: a central zone of β cells; an intermediate zone with agranular cells (the delta and pancreatic polypeptide cells); an outer zone of α cells. This normal pattern, best seen in the developing human fetus may have a functional significance in the regulation of the secretion of glucagon and insulin by α and β cells.