Electron microscopic immunocytochemical localization of glucagon and pancreatic polypeptide in rat pancreas: characterization of a population of islet cells containing both peptides.

The distribution of glucagon and pancreatic polypeptide was studied immunocytochemically in rat pancreas at both light and electron microscopic levels. My earlier observation that these two peptides are distributed in three cell types--cells containing glucagon, cells containing pancreatic polypeptide, and cells containing both--was confirmed at the electron microscopic level. In the glucagon-pancreatic polypeptide cells, the immunoreactivities of the two peptides were present in the same secretion granules. In addition, these glucagon and pancreatic polypeptide-containing granules were morphologically distinct from glucagon granules but similar to pancreatic polypeptide granules and somatostatin granules.