Cytosolic free Ca2+ in insulin secreting cells and its regulation by isolated organelles |
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Authors: | M. Prentki C. B. Wollheim |
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Affiliation: | (1) Institut de biochimie clinique, University of Geneva, Sentier de la Roseraie, CH-1211 Geneva 4, (Switzerland) |
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Abstract: | Summary The role of Ca2+ in secretagogue-induced insulin release is documented not only by the measurements of45Ca fluxes in pancreatic islets, but also, by direct monitoring of cytosolic free Ca2+, [Ca2+]i. As demonstrated, using the fluorescent indicator quin 2, glyceraldehyde, carbamylcholine and alanine raise [Ca2+]i in the insulin secreting cell line RINm5F, whereas glucose has a similar effect in pancreatic islet cells. The regulation of cellular Ca2+ homeostasis by organelles from a rat insulinoma, was investigated with a Ca2+ selective electrode. The results suggest that both the endoplasmic reticulum and the mitochondria participate in this regulation, albeit at different Ca2+ concentrations. By contrast, the secretory granules do not appear to be involved in the short-term regulation of [Ca2+]i. Evidence is presented that inositol 1,4,5-trisphosphate, which is shown to mobilize Ca2+ from the endoplasmic reticulum, is acting as an intracellular mediator in the stimulation of insulin release. |
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Keywords: | Pancreatic B-cell insulin secretion cytosolic free Ca2+ |
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