Signaling mechanisms underlying the insulinotropic effect of pituitary adenylate cyclase-activating polypeptide in HIT-T15 cells

Endocrinology. 1996 Jul;137(7):2791-8. doi: 10.1210/endo.137.7.8770899.

Abstract

The signaling mechanisms underlying the insulinotropic effect of the pancreatic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) were studied in insulin-producing HIT-T15 cells. It was found that unlabeled PACAP38 dose-dependently displaced [125I]PACAP27 from HIT-T15 cell membranes, showing binding of the peptide to these cells. Furthermore, at levels above 0.1 nM, PACAP38 stimulated insulin secretion in a Ca2+ -dependent manner, requiring 0.5 mM glucose. The peptide also markedly increased the cellular cAMP content and slightly stimulated the formation of inositol phosphates. Moreover, PACAP38 elevated the cytoplasmic Ca2+ concentration ([Ca2+]cyt) in fura-2-AM-loaded cell suspensions. The PACAP38-induced increase in cellular cAMP content was also seen at zero glucose, whereas the increases in insulin secretion and [Ca2+]cyt were abolished by removal of glucose or extracellular Ca2+. We conclude that PACAP38 binds to HIT-T15 cell membranes and acts in a glucose-dependent manner on adenylate cyclase to form cAMP, which both directly and indirectly, through increased [Ca2+]cyt, stimulates exocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding, Competitive
  • Calcium / metabolism
  • Cell Line
  • Colforsin / pharmacology
  • Cricetinae
  • Cyclic AMP / metabolism
  • Cytoplasm / metabolism
  • Egtazic Acid / pharmacology
  • Fluorescent Dyes
  • Fura-2 / analogs & derivatives
  • Inositol Phosphates / metabolism
  • Insulin / metabolism*
  • Insulin / pharmacology
  • Insulin Secretion
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / metabolism*
  • Kinetics
  • Mesocricetus
  • Neuropeptides / metabolism*
  • Neuropeptides / pharmacology*
  • Neurotransmitter Agents / metabolism
  • Neurotransmitter Agents / pharmacology
  • Pituitary Adenylate Cyclase-Activating Polypeptide
  • Signal Transduction*

Substances

  • Fluorescent Dyes
  • Inositol Phosphates
  • Insulin
  • Neuropeptides
  • Neurotransmitter Agents
  • Pituitary Adenylate Cyclase-Activating Polypeptide
  • fura-2-am
  • Colforsin
  • Egtazic Acid
  • Cyclic AMP
  • Calcium
  • Fura-2