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ludc web

Lena Eliasson

Principal investigator

ludc web

Somatostatin, misoprostol and galanin inhibit gastrin- and PACAP-stimulated secretion of histamine and pancreastatin from ECL cells by blocking specific Ca(2+) channels.

Author

  • Maria Björkqvist
  • Maria Lundgren
  • Lena Eliasson
  • Rolf Håkanson
  • Erik Lindström

Summary, in English

The oxyntic mucosa is rich in ECL cells. They secrete histamine and chromogranin A-derived peptides, such as pancreastatin, in response to gastrin and pituitary adenylate cyclase-activating peptide (PACAP). Secretion is initiated by Ca2+ entry. While gastrin stimulates secretion by opening L-type and N-type Ca2+ channels, PACAP stimulates secretion by activating L-type and receptor-operated Ca2+ channels. Somatostatin, galanin and prostaglandin E2 (PGE2) inhibit gastrin- and PACAP-stimulated secretion from the ECL cells. In the present study, somatostatin and the PGE2 congener misoprostol inhibited gastrin- and PACAP-stimulated secretion 100%, while galanin inhibited at most 60–65%. Bay K 8644, a specific activator of L-type Ca2+ channels, stimulated ECL-cell secretion, an effect that was inhibited equally effectively by somatostatin, misoprostol and galanin (75–80% inhibition). Pretreatment with pertussis toxin, that inactivates inhibitory G-proteins, prevented all three agents from inhibiting stimulated secretion (regardless of the stimulus). Pretreatment with nifedipine (10 μM), an L-type Ca2+ channel blocker, reduced PACAP-evoked pancreastatin secretion by 50–60%, gastrin-evoked secretion by not, vert, similar 80% and abolished the response to Bay K 8644. The nifedipine-resistant response to PACAP was abolished by somatostatin and misoprostol but not by galanin. Gastrin and PACAP raised the intracellular Ca2+ concentration in a biphasic manner, believed to reflect mobilization of internal Ca2+ followed by Ca2+ entry. Somatostatin and misoprostol blocked Ca2+ entry (and histamine and pancreastatin secretion) but not mobilization of internal Ca2+.



The present observations on isolated ECL cells suggest that Ca2+ entry rather than mobilization of internal Ca2+ triggers exocytosis, that gastrin and PACAP activate different (but over-lapping) Ca2+ channels, that somatostatin, misoprostol and galanin interact with inhibitory G-proteins to block Ca2+ entry via L-type Ca2+ channels, and that somatostatin and misoprostol (but not galanin) in addition block N-type and/or receptor-operated Ca2+ channels.

Department/s

  • Translational Neuroendocrinology
  • Department of Experimental Medical Science
  • Biomarkers in Brain Disease
  • Division of Microbiology, Immunology and Glycobiology - MIG
  • Diabetes - Islet Cell Exocytosis
  • Drug Target Discovery

Publishing year

2005

Language

English

Pages

81-90

Publication/Series

Regulatory Peptides

Volume

130

Issue

1-2

Document type

Journal article

Publisher

Elsevier

Topic

  • Cell and Molecular Biology

Keywords

  • Gastrin
  • PACAP
  • Bay K 8644
  • PRL-2903
  • Galanin
  • Somatostatin
  • PGE2
  • Misoprostol

Status

Published

Research group

  • Translational Neuroendocrinology
  • Biomarkers in Brain Disease
  • Diabetes - Islet Cell Exocytosis
  • Drug Target Discovery

ISBN/ISSN/Other

  • ISSN: 1873-1686