Immunocytochemical localization of prosomatostatin fragments in maturing and mature secretory granules of pancreatic and gastrointestinal D cells.

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Abstract
Pancreatic and gastrointestinal D [human] cells were examined by immunocytochemistry using antisera against somatostatin-28 (SS28) and its NH2-terminal fragment SS28-(1-12), followed by the staphylococcal protein A-gold (pAg) complex. In pancreatic and gastric D cells incubated with antiserum against SS28-(1-12), the Ag particles produced intense staining of the mature secretory granules but weaker staining of the immature granules associated with the Golgi area; after SS28 antiserum treatment, the particles accumulated selectively over the population of immature secretory granules. In intestinal D cells, not only SS28-(1-12) but also SS28 antiserum produced an intense Ag staining over the mature .delta. granules. The relative amounts of immunoreactive sites related to SS28 and its cleavage product SS28-(1-12) in maturing and mature secretory granules are evidently different in pancreatic, gastric and intestinal D cells.