Different modes of action of the imidazoline compound RX871024 in pancreatic β-cells. Blocking of K+ channels, mobilization of Ca2+ from endoplasmic reticulum, and interaction with exocytotic machinery

Sergei V. Zaitsev, A. M. Efanov, A. Raap, I. B. Efanova, J. Schloos, B. Steckel-Hamann, O. Larsson, C. G. Östenson, P. O. Berggren, H. J. Mest, S. Efendic

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Abstract

The imidazoline compound RX871024 glucose-dependently potentiates the release of insulin in pancreatic islets and β-cell lines. This activity of the compound is not related to its action by stimulating α2-adrenoceptors and I1- and I2-imidazoline receptors. There are at least three modes of action of RX871024 in β-cells: (1) RX871024 blocks the ATP-dependent, Ca2+-activated, and delayed rectifier K+ channel activity; (2) RX871024 causes mobilization of Ca2+ from thapsigargin-sensitive intracellular stores, the effect probably controlled by cytochrome P450; and (3) the stimulatory activity of RX871024 on insulin release involves interaction of the compound with the exocytotic machinery, unrelated to the changes in membrane potential and cytoplasmic-free Ca2+ concentration, whereas protein phosphorylation plays an important role in this process. The maximal insulinotropic effect of RX871024 is much higher than that of the sulfonylurea glibenclamide. RX871024 stimulates insulin release and normalizes blood glucose levels in rats in vivo without affecting blood pressure and heart rate.

Original languageEnglish (US)
Pages (from-to)241-252
Number of pages12
JournalAnnals of the New York Academy of Sciences
Volume881
DOIs
StatePublished - Jan 1 1999

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ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • History and Philosophy of Science

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