Immunocytochemical colocalizations of serotonin, aromatic L-amino acid decarboxylase and polypeptide hormones in A- and PP-cells of the chicken endocrine pancreas

Adrenomedullin in nonmammalian vertebrate pancreas: an immunocytochemical study

Adrenomedullin (AM) immunoreactive cells have been identified, by immunocytochemical methods, in the endocrine pancreas of seven nonmammalian vertebrate species, belonging to the cartilaginous and bony fish, amphibian, reptilian, and bird classes. The frequency and distribution of the pancreatic AM cells vary among the different animals. In most species, these cells are found scattered mainly among the exocrine component, with a few present in the islet-like structures. The distribution of AM cells in both fish species and Xenopus shows an inverse pattern, since almost every AM cell is located in the islets. In addition, the colocalization of AM with other classical pancreatic peptide immunoreactivities has been analyzed. In numerous cells, AM immunoreactivity did not colocalize with the other hormones, suggesting that AM-producing cells might constitute a new endocrine cell type in the pancreas of many species. Nevertheless, in other cells a species-specific pattern of colocalizations with insulin, somatostatin, glucagon, and pancreatic polypeptide was found, indicating that complex interactions among all these hormones may occur. In conclusion, AM represents a new regulatory peptide of the endocrine nonmammalian vertebrate pancreas, which is possibly involved in the modulation of insulin secretion and other pancreatic functions.

Immunocytochemical colocalizations of insulin, aromatic L-amino acid decarboxylase, dopamine beta-hydroxylase, S-100 protein and chromogranin A in B-cells of the chicken endocrine pancreas

The colocalization of aromatic L-amino acid decarboxylase (AADC), dopamine beta-hydroxylase (DBH), S-100 protein and chromogranin A (CgA) in the insulin-containing B-cells of the chicken endocrine pancreas was investigated by using light microscopic immunohistochemistry and combined pre-embedding immunoperoxidase and post-embedding immunogold electron microscopic immunocytochemistry. Using the post-embedding method, immunoreactivity against the anti-insulin serum by protein A-gold technique was observed in the core of all types of B-cell granules. Immunoreaction with anti-S-100 protein serum was detected in the core of all types of B-cell granules. Immunoreaction with anti-S-100 protein serum was detected in the core of all types of B-cell granules from non-osmicated tissues even by post-embedding method, but immunoreactivities against the anti-AADC, DBH and CgA sera were only demonstrable in crystalloid granules of B-cells by pre-embedding method. Immunoreaction with the anti-CgA serum was also detected in the cytoplasmic matrix around crystalloid granules and also in the dense bodies showing immunonegative with anti-insulin serum. From these results, it seems likely that S-100 protein co-stored all types of B-cell granules involved in the maturation of granules, and AADC, DBH and CgA are related to the synthesis of noradrenaline in crystalloid granules of B-cells.