Immunocytochemical identification of cells containing insulin, glucagon, somatostatin, and pancreatic polypeptide in islets of Langerhans of the wombat pancreas with electron microscopy.

The endocrine pancreas of the southern hairy-nosed wombat (Lasiorhinus latifrons) was investigated by means of electron-microscope immunocytochemistry using the protein A--gold technique on London resin (LR) white-embedded tissue. The primary antibodies used were raised against insulin, glucagon, somatostatin and pancreatic polypeptide. The morphology of the secretory granules differed in the four cell types. The insulin cells are pleiomorphic, and the secretory granules composed of an electron-dense core surrounded by an electron-lucent halo. The glucagon cells possess granules of varying density. Somatostatin cells have large, less dense secretory granules. The pancreatic polypeptide cells show small dense secretory granules. It is essential that it be corroborated by immunocytochemical data at the light or preferably electron-microscopical level for the definite identification of endocrine cell types. Recent developments in immuno-electron-microscopic techniques have contributed to a better knowledge of cells responsible for the secretion of a wide variety of hormones, as in this study.