Identification of the Pancreatic Endocrine Cells of Pseudemys scripta elegans by Immunogold Labeling

Abstract

The endocrine pancreatic cells of Pseudemys scripta elegans were investigated immunocytochemically by light and electron microscopy. Insulin-, somatostatin (SST)-1, SST-28 (1-12)-, salmon (s)SST-25-, glucagon-, pancreatic polypeptide (PP)-, peptide tyrosine tyrosine (PYY)-, and neuropeptide tyrosine (NPY)-like immunoreactivities were observed. Insulin cells were immunogold labeled with bonito insulin antiserum and secretory granules were characterized by a wide halo and a dense core of varying shape. Consecutive PAP-immunostained sections showed that SST-28 (1–12), SST-14, and sSST-25 immunoreactivities occurred in the same cells. However, preabsorption tests demonstrated that anti-sSST-25 serum detected the invariant SST-14 molecule. The SST-28 (1–12)/SST-14-immunogold-labeled cells mainly had round or ovoid medium electron-dense granules. Glucagon-IR cells were characterized by round secretory granules with an electron-dense core, with or without a narrow clear halo. There were PP, PYY, and NPY (NPY-like) immunoreactivities in a population of glucagon-IR cells in the pancreatic duodenal region (glucagon/NPY cells). Most of the secretory granules of these glucagon/NPY-like cells had an electron-dense content and were round, although there were also pyriform or ovoid secretory granules which were smaller than those of glucagon-IR cells. Preabsorption tests proved that the NPY-like peptides detected in the endocrine pancreas of P. scripta elegans were more similar to NPY or PYY than to PP.