Glucose-induced electrical activity in beta-cells. Feedback control of ATP-sensitive K+ channels by Ca2+? [corrected].
Glucose regulates Ca2+ influx in beta-cells by controlling a rhythmic electrical activity (slow waves with spikes). However, the glucose-sensitive feedback system that triggers repolarization at the end of the slow waves, and thus stops Ca2+ influx, is unknown. Raising extracellular Ca2+ to 10 mM shortened slow waves in mouse beta-cells perifused with medium containing 15 mM glucose and restored slow waves when persistent depolarization and continuous spike activity were induced by 30 mM glucose. The effects of high Ca2+ were reversed or prevented by tolbutamide, whereas 1 mM tetraethylammonium only increased spike amplitude. This suggests that a feedback action of Ca2+ on ATP-sensitive K+ channels rather than on voltage- and Ca2(+)-activated K+ channels may be involved in slow wave generation. Metabolic modulation of this feedback could be central in the regulation of electrical activity and, hence, insulin release.
Henquin
J C
JC
First Institute of Physiology, University of Saarland, Homburg/Saar, Federal Republic of Germany.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D004553:Electric Conductivity / Q000187:drug effects / Q000502:physiology; D004594:Electrophysiology; D005246:Feedback / Q000187:drug effects / Q000502:physiology; D005260:Female; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014044:Tolbutamide / Q000494:pharmacology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D000255:Adenosine Triphosphate; D014044:Tolbutamide; D005947:Glucose; D002118:Calcium