Identification of four endocrine cell types in the pancreas of Cottus scorpius (Teleostei) by immunofluorescence and electron microscopy

Abstract

Much of the endocrine pancreas of the teleost fish, Cottus scropius (the daddy sculpin), is concentrated into two large (2–3 mm diameter) structures called Brockmann bodies or principal islets (PI). Using indirect immunofluorescence, we have localized the endocrine cell types present in the principal islets of this fish; the cells were identified in the electron microscope by comparison of ultrathin sections with their serial immunostained semithin sections. The juxtapyloric Brockmann body contained insulin-, glucagon-, somatostatin-, and pancreatic polypeptide (PP)-immunofluorescent cells; the juxtasplenic Brockmann body showed insulin-, glucagon-, and somatostatin-containing cells but no PP cells. Electron microscopical observation of the four cell types revealed differences in the shape, size, and electron density of their respective secretory granules, allowing each type to be assigned to a distinct ultrastructural category.