Synchronization of pancreatic beta-cell rhythmicity after glucagon induction of Ca2+ transients.
Pancreatic beta-cells are biological oscillators requiring a coupling force for the synchronization of the cytoplasmic Ca(2+) oscillations responsible for pulsatile insulin release. Testing the idea that transients, superimposed on the oscillations, are important for this synchronization, the concentration of cytoplasmic Ca(2+) ([Ca(2+)](i)) was measured with ratiometric fura-2 technique in single beta-cells and small aggregates prepared from islets isolated from ob/ob-mice. Image analyses revealed asynchronous [Ca(2+)](i) oscillations in adjacent beta-cells lacking physical contact. The addition of glucagon stimulated the firing of [Ca(2+)](i) transients, which appeared in synchrony in adjacent beta-cells. Moreover, the presence of glucagon promoted synchronization of the [Ca(2+)](i) oscillations in beta-cells separated by a distance <100 microm but not in those >200 microm apart. The results support the proposal that the repolarizing effect of [Ca(2+)](i) transients provides a coupling force for co-ordinating the pulses of insulin release generated by pancreatic beta-cells.
Grapengiesser
E
E
Department of Medical Cell Biology, Uppsala University, Biomedicum Box 571, Uppsala SE-751 23, Sweden.
Dansk
H
H
Hellman
B
B
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D016257:Fura-2; D005934:Glucagon / Q000378:metabolism* / Q000494:pharmacology; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008820:Mice, Obese; D010507:Periodicity
D005934:Glucagon; D002118:Calcium; D016257:Fura-2