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  • Title: Synchronous oscillations of cytoplasmic Ca2+ and insulin release in glucose-stimulated pancreatic islets.
    Author: Bergsten P, Grapengiesser E, Gylfe E, Tengholm A, Hellman B.
    Journal: J Biol Chem; 1994 Mar 25; 269(12):8749-53. PubMed ID: 8132606.
    Abstract:
    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.
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