Evidence of pituitary adenylate cyclase activating polypeptide (PACAP) in pancreatic islet cells by confocal microscopy

Several studies have shown that pituitary adenylate cyclase activating poly peptide (PACAP) stimulates at very low Concentration insulin release from p ancreatic beta cells. In addition, PACAP has been evidenced in pancreatic n ervous fibers surrounding the islets, the core of the islet, and the capill aries. The aim of the present study was to demonstrate internalization of P ACAP in pancreatic islet cells. Pancreatic islets were obtained from Wistar rat pancreata by modified Lacy's isolation method, The isolated islets wer e incubated in the presence of Fluo-PACAP 27, a fluorescent ligand specific : fur PACAP receptors. At the end of incubation the islets were fixed in po raformaldehyde and then observed by confocal microscope. Fluo-PACAP 27 was internalized into pancreatic islet cells, and this process was time- and te mperature-dependent (37 degreesC). The fluorescent molecules converged towa rd the nucleus where an intense fluorescence was evidenced after 60 minutes , Incubation with phenyl arsine oxide as well as with PACAP 6-38, a recepto r antagonist, prevented the internalization process. Further studies are re quired to explain the internalization process of PACAP 27 into the nucleus of pancreatic islet cells.