Identification of the pancreatic endocrine cells of Pseudemys scripta elegans by immunogold labeling

The endocrine pancreatic cells of Psuedemys scripta elegans were in investi gated immunocytochemically by light and electron microscopy Insulin-, somat ostatin (SST)-1, SST-28 (1-12)-, salmon (s)SST-25-, glucagon-, pancreatic p olypeptide (PP)-, peptide tyrosine tyrosine (PYY)-, and neuropeptide tyrosi ne (NPY)-like immunoreactivities were observed. Insulin cells were immunogo ld labeled with bonito insulin antiserum and secretory granules were charac terized by a wide halo and a dense core of varying shape. Consecutive PAP-i mmunostained sections showed that SST-28 (1-12), SST-14, and sSST-25 immuno reactivities occurred in the same cells. However, preabsorption tests demon strated 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 me dium electrondense granules. Glucagon-IR cells were characterized by round secretory granules with an electron-dense core, with or without a narrow cl ear halo. There were PP PYY, and NPY (NPY-like) immunoreactivities in a pop ulation of glucagon-IR cells in the pancreatic duodenal region (glucagon/NP Y cells). Most of the secretory granules of these glucagon/NPY-like cells h ad an electron-dense content and were round, although there were also pyrif orm or ovoid secretory granules which were smaller than those of glucagon-I R cells. Preabsorption tests proved that the NPY-like peptides detected in the endocrine pancreas of P. scripta elegans were more similar to NPY or PY Y than to PP. (C) 2000 Academic Press.