Cytosolic free Ca2+ in insulin secreting cells and its regulation by isolated organelles.
The role of Ca2+ in secretagogue-induced insulin release is documented not only by the measurements of 45Ca 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.
D000227:Adenine Nucleotides / Q000378:metabolism; D000409:Alanine / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism; D004987:Ethers / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D005985:Glyceraldehyde / Q000494:pharmacology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000502:physiology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D015759:Ionomycin; D007515:Islets of Langerhans / Q000166:cytology*; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D009940:Organoids / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology
D000227:Adenine Nucleotides; D004987:Ethers; D007295:Inositol Phosphates; D007328:Insulin; D005985:Glyceraldehyde; D000001:Calcimycin; D015759:Ionomycin; D015544:Inositol 1,4,5-Trisphosphate; D014700:Verapamil; D005947:Glucose; D000409:Alanine; D002118:Calcium