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The controlled flux of calcium across the cell membrane is intimately linked to the release of insulin from pancreatic beta-cells, but the uncontrolled influx of calcium is a common final denominator of cell death. Because interleukin 1 has been shown to be cytotoxic to beta-cells in isolated rat islets of Langerhans and since interleukin 1 has a calcium ionophore effect on other cell types, this study was designed to test whether alterations of the calcium flux across the beta-cell membrane would influence the effects of interleukin 1 on isolated rat and mouse islets. Further, the cytosolic free Ca2+ concentration was measured by the fura-2 method in rat islets during acute interleukin 1 exposure. Treatment with 10 µmol/l of verapamil (a potent blocker of the voltage-dependent calcium channel) tended to suppress the inhibitory effect of interleukin 1 on insulin release from rat islets, suggesting protection against cytotoxicity. Conversely, a stimulatory effect of interleukin 1 on mouse islets during 6 days of exposure to interleukin 1 was turned into inhibition by high extracellular calcium concentration. Interleukin 1 did not have any acute effect on cytosolic free Ca2+ concentration. In conclusion, interleukin 1 has no specific calcium ionophore effect on beta-cells, but alterations of the calcium flux across the beta-cell membrane influence the functional effects of interleukin 1, suggesting interference with cell function and toxicity, which would likely be accompanied by an uncontrolled influx of calcium.
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J. Storling, S. V. Zaitsev, I. L. Kapelioukh, A. E. Karlsen, N. Billestrup, P.-O. Berggren, and T. Mandrup-Poulsen Calcium Has a Permissive Role in Interleukin-1{beta}-Induced c-Jun N-Terminal Kinase Activation in Insulin-Secreting Cells Endocrinology, July 1, 2005; 146(7): 3026 - 3036. [Abstract] [Full Text] [PDF] |
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