title: Pancreatic beta cells synthesize neuropeptide Y and can rapidly release peptide co-transmitters.
abstract: BACKGROUND
  In addition to polypeptide hormones, pancreatic endocrine cells synthesize a variety of bioactive molecules including classical transmitters and neuropeptides. While these co-transmitters are thought to play a role in regulating hormone release little is known about how their secretion is regulated. Here I investigate the synthesis and release of neuropeptide Y from pancreatic beta cells.
  
  
  RESULTS
  NPY appears to be an authentic co-transmitter in neonatal, but not adult, beta cells because (1) early in mouse post-natal development, many beta cells are NPY-immunoreactive whereas no staining is observed in beta cells from NPY knockout mice; (2) GFP-expressing islet cells from an NPY(GFP) transgenic mouse are insulin-ir; (3) single cell RT-PCR experiments confirm that the NPY(GFP) cells contain insulin mRNA, a marker of beta cells. The NPY-immunoreactivity previously reported in alpha and delta cells is therefore likely to be due to the presence of NPY-related peptides. INS-1 cells, a beta cell line, are also NPY-ir and contain NPY mRNA. Using the FMRFamide tagging technique, NPY secretion was monitored from INS-1 beta cells with high temporal resolution. Peptide release was evoked by brief depolarizations and was potentiated by activators of adenylate cyclase and protein kinase A. Following a transient depolarization, NPY-containing dense core granules fused with the cell membrane and discharged their contents within a few milliseconds.
  
  
  CONCLUSIONS
  These results indicate that after birth, NPY expression in pancreatic islets is restricted to neonatal beta cells. The presence of NPY suggests that peptide co-transmitters could mediate rapid paracrine or autocrine signaling within the endocrine pancreas. The FMRFamide tagging technique may be useful in studying the release of other putative islet co-transmitters in real time.
authors.affiliation: Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America. mwhim@lsuhsc.edu
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Whim
mesh_terms: D000818:Animals; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D019835:FMRFamide / Q000494:pharmacology; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D050417:Insulin-Secreting Cells / Q000166:cytology*; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence / Q000379:methods; D009478:Neuropeptide Y / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D009478:Neuropeptide Y; D010455:Peptides; D049452:Green Fluorescent Proteins; D019835:FMRFamide