Diabetes, Vol 39, Issue 11 1457-1460, Copyright © 1990 by American Diabetes Association
Glucose-induced electrical activity in beta-cells. Feedback control of ATP-sensitive K+ channels by Ca2+? [corrected]
JC Henquin
First Institute of Physiology, University of Saarland, Homburg/Saar, Federal Republic of Germany.
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.