PHYLOGENIC STUDY OF CALCITONIN-GENE-RELATED PEPTIDE-IMMUNOREACTIVE STRUCTURES IN THE PANCREAS

The immunohistochemical localization of calcitonin gene-related peptid e was examined, at both light and electron microscopic levels, in the pancreas of various vertebrates, including the eel, bullfrog, turtle, chicken, mouse, rat, guinea pig, dog, monkey, and human. Immunoreactiv e staining was observed in nerve fibers in every animal species examin ed, but positive endocrine cells were limited to the rat, monkey, and human. The density of the positive endocrine cells varied considerably among the three species (monkey > rat > human). Positive nerve fibers were distributed throughout the parenchyma, being particularly rich a round pancreatic ducts, and near large or small blood vessels. In four species (eel, mouse, rat, and dog), positive nerve fibers formed a de nse network in the islet region. There were positive varicose nerve fi bers around exocrine cells. These fibers, varying in density in differ ent species (relatively high in the eel, bullfrog, and rat), were some times adjacent to acinar cells. At the electron microscopic level, pos itive nerve terminals were often demonstrated in close apposition to t he outer membrane of acinar cells. The eel pancreas revealed an except ional pattern of staining in neuronal cell bodies that were scattered in the interlobular connective tissue. Despite these anatomical differ ences, the omnipresence of this peptide suggests its essential role(s) in the pancreas.