Synchronization of pancreatic beta-cell rhythmicity after glucagon induction of Ca2+ transients |
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Authors: | Grapengiesser E Dansk H Hellman B |
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Institution: | Department of Medical Cell Biology, Uppsala University, Biomedicum Box 571, Uppsala SE-751 23, Sweden. |
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Abstract: | 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. |
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