Cell composition and co-stored peptides in the endocrine pancreas of Rana arvalis.

The endocrine pancreas of Rana arvalis studied by immunochemistry consisted of islets and diffuse endocrine cells. The islets showed a mammalian-like arrangement with a central core of B cells and a peripheral mantle of A/PP cells. A few D and vasoactive intestinal polypeptide cells were also present. Consecutive sections or double-labeling studies allowed us to detect several regulatory peptides colocalized in the same endocrine cells. The so-called A/PP cells contained subpopulations of cells showing various types of immunoreactivity and varying degrees of immunolabeling. Generally, glucagon/pancreatic polypeptide, glucagon/pancreatic polypeptide/phe-met-arg-phe-amide, glucagon/pancreatic polypeptide/peptide tyrosine tyrosine, glucagon/pancreatic polypeptide/peptide tyrosine tyrosine/phe-met-arg-phe-amide immunoreactivities were present in the islets, while peptide tyrosine tyrosine/neuropeptide tyrosine colocalization was also found in the parenchyma.