Immunocytochemical study of the endocrine pancreas in the grey kangaroo (Macropus fuliginosus)

The endocrine pancreas of the grey kangaroo, Macropus fuliginosus, was investigated by means of immunocytochemistry using the PAP method on the same section at the light- and electron-microscopic levels. Semithin plastic sections were stained individually with primary antibodies for insulin, glucagon, somatostatin and pancreatic polypeptide (PP), and then photographed. Sections were osmicated, re-embedded in BEEM capsules, and ultrathin sections made and examined. The same labelled cells as in the semithin sections were localised in the thin sections, photographs taken and the morphology of secretory granules studied. The insulin cells were pleomorphic; their secretory granules displayed an electron-dense core surrounded by an empty halo. The glucagon cells possessed granules with an electron-dense core usually surrounded by a halo of less dense granular material. Somatostatin cells had larger, less dense secretory granules. The PP cells showed small, dense secretory granules. In order for an ultrastructural study to be considered reliable for the definite identification of endocrine cell types, it is essential that it be corroborated by correlated immunocytochemical data at the light- and electron-microscopic levels.