Synchronous oscillations of cytoplasmic Ca2+ and insulin release in glucose-stimulated pancreatic islets.
The cytoplasmic Ca2+ concentration ([Ca2+]i) was measured in single pancreatic mouse islets superfused in a system allowing concomitant recordings of insulin release. When glucose was raised from 3 to 11 mM, [Ca2+]i responded by a transient lowering followed by a rise to an average level of 192 +/- 11 nM. In 77% of the islets the rise was associated with the gradual appearance of oscillations, which were either fast (2-7/min), slow (0.3-0.9/min), or a combination of both types. The characteristics of the fast [Ca2+]i oscillations were those expected from a relationship with the electrical burst activity in islets. Accordingly, in most cases the fast oscillations were remarkably regular. The slow [Ca2+]i oscillations had characteristics similar to the large amplitude ones in individual beta-cells. Whereas glucagon and dibutyryl cAMP could transform slow islet oscillations into fast ones, the alpha 2-adrenergic agonist clonidine had the opposite effect. The rapid islet oscillations were also facilitated by elevated concentrations of extracellular Ca2+. Reinforcing the arguments for [Ca2+]i oscillations as responsible for a pulsatile insulin secretion it was possible to demonstrate that the release of the hormone from single islets is synchronized with the slow [Ca2+]i oscillations.
Bergsten
P
P
Department of Medical Cell Biology, Uppsala University, Sweden.
Grapengiesser
E
E
Gylfe
E
E
Tengholm
A
A
Hellman
B
B
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D005934:Glucagon / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D008820:Mice, Obese; D010507:Periodicity
D007328:Insulin; D003994:Bucladesine; D005934:Glucagon; D005947:Glucose; D002118:Calcium