Determination of target cells for Cholecystokinin in the porcine pancreas

Abstract

The cholecystokinin (CCK) family of peptides and receptors is present throughout the brain and gastrointestinal tract including pancreatic tissue. The expression of these molecules in the gut and pancreas is species-specifically regulated and the role of CCK in porcine pancreatic islet hormone secretion is still a matter of discussion. Therefore, in this study we have determined the cell-type specific localization of and its high affinity CCKA-receptor in islet cells using immunohistochemical techniques. Serial sectioning followed by double-immunostaining of methanol/acetic acid-fixed, paraffin-embedded pancreatic tissues were performed with antibodies against CCK, CCKA-receptor, glucagon and somatostatin. To determine whether CCK specific mRNA is locally expressed, total RNA was isolated, transcribed to cDNA and analysed with specific primer for CCK gene expression. Our results clearly show that CCK and the CCKA-receptor coexist in glucagon--but not in somatostatin-producing cells. Moreover our RT-PCR experiments demonstrate that there is no local gene expression of CCK in the porcine pancreas. Our results provide evidence that, in the porcine species, blood-borne CCK binds specifically to the CCKA-receptor and may thereby modulate the glucose homeostasis via a direct action on A-cells.