The ultrastructural identity of pancreatic polypeptide cells in chicks.

A very similar ultrastructure has been attributed to pancreatic polypeptide and somatostatin cells in chickens. In order to characterize any possible differences between them, cells shown to be immunoreactive for these hormones in semi-thin sections of chick pancreas were identified in adjacent thin sections prepared for conventional electron microscopy. In this way the ultrastructural features of the immunoreactive cells could be determined. In general, in somatostatin-immunoreactive cells, granule profiles are almost exclusively round, whereas in pancreatic polypeptide cells there are elongate as well round profiles. Within cells of both types the electron density of the granule matrix varies from one granule to another, but the range of density is greater in pancreatic polypeptide granules. The latter are slightly smaller than somatostatin granules.