Cytoplasmic Ca2+ in glucagon-producing pancreatic alpha-cells exposed to carbachol and agents affecting Na+ fluxes

Endocrine. 1997 Feb;6(1):79-83. doi: 10.1007/BF02738806.


The cytoplasmic Ca2+ concentration ([Ca2+]i) was measured with dual wavelength fluorometry in glucagon-producing mouse pancreatic alpha-cells loaded with the indicator fura-2. Spontaneous rhythmic activity in terms of slow oscillations from a basal level was observed at 3 mM glucose. Like in the insulin-secreting beta-cells the generation of [Ca2+]i oscillations in the alpha-cells was affected by the activity of the Na/K pump. Blocking the pump with ouabain resulted in an initial rise of [Ca2+]i followed by gradual return to the basal level. The oscillations were transformed into sustained elevation of [Ca2+]i by 10 mM L-glycine, which is cotransported with Na+. A similar but less pronounced effect was obtained when Na+ was cotransported with 10 mM of the nonmetabolizable amino acid alpha-amino-isobutyric acid. L-glycine induced sustained increase of [Ca2+]i also when the oscillatory activity was suppressed by exposing the alpha-cells to 20 mM glucose in the presence of insulin. The observation that carbachol induces a [Ca2+]i response in isolated alpha-cells calls for reconsideration of current ideas that muscarinic stimulation of glucagon release is an indirect effect mediated by adjacent beta-cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminoisobutyric Acids / pharmacology
  • Animals
  • Calcium / metabolism*
  • Carbachol / pharmacology*
  • Cytoplasm / drug effects
  • Cytoplasm / metabolism*
  • Female
  • Fluorescent Dyes
  • Fura-2
  • Glucagon / biosynthesis*
  • Glycine / pharmacology
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / metabolism*
  • Mice
  • Muscarinic Agonists / pharmacology*
  • Signal Transduction / physiology
  • Sodium / metabolism*
  • Sodium Channels / drug effects
  • Sodium Channels / metabolism
  • Sodium-Potassium-Exchanging ATPase / metabolism


  • Aminoisobutyric Acids
  • Fluorescent Dyes
  • Muscarinic Agonists
  • Sodium Channels
  • 2-aminoisobutyric acid
  • Carbachol
  • Glucagon
  • Sodium
  • Sodium-Potassium-Exchanging ATPase
  • Calcium
  • Glycine
  • Fura-2