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PACAP is expressed in secretory granules of insulin and glucagon cells in human and rodent pancreas - Evidence for generation of cAMP compartments uncoupled from hormone release in diabetic islets

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Author

  • GM Portela-Gomes
  • A Lukinius
  • Otto Ljungberg
  • S Efendic
  • Bo Ahrén
  • SM Abdel-Halim

Summary, in English

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an islet neuropeptide with potent insulinotropic action. The current study investigates PACAP expression in normal human and rat pancreatic islets, and whether it is altered in diabetic state. To that end, PACAP immunoreactivity was studied by immunofluorescence methods enhanced by the catalyzed reporter deposition (CARD) technique. Insulin and cyclic adenosine monophosphate (cAMP) generation induced by PACAP were investigated in islets isolated from the spontaneously diabetic Goto-Kakizaki (GK) rat. PACAP immunoreactivity was observed in virtually all insulin and glucagon cells in both species, but not in somatostatin or pancreatic polypeptide (PP) cells; this co-localization pattern was unaltered in diabetic pancreata. In normal human pancreas, PACAP was further localized ultrastructurally to the secretory granules of insulin and glucagon cells. PACAP significantly potentiated glucose-stimulated insulin release in isolated islets of normal but not of GK rats. PACAP failed to enhance cAMP generation in normal islets, but induced similar to 5-folds exaggeration in the diabetic islets. In conclusion, using improved immunocytochemistry techniques and electron microscopy (EM), PACAP was shown to be expressed both in normal and diabetic islet cells and localized to secretory granules of insulin and glucagon cells. Furthermore, the insulinotropic action of PACAP was markedly impaired in diabetic islets in spite of exaggerated cAMP response. (C) 2003 Elsevier Science B.V. All rights reserved.

Publishing year

2003

Language

English

Pages

31-39

Publication/Series

Regulatory Peptides

Volume

113

Issue

1-3

Document type

Journal article

Publisher

Elsevier

Topic

  • Cell and Molecular Biology

Keywords

  • human
  • type-2 diabetes
  • pancreas
  • PACAP
  • cAMP
  • experimental diabetes

Status

Published

Research group

  • Pathology, Malmö

ISBN/ISSN/Other

  • ISSN: 1873-1686