Agonist-evoked mitochondrial Ca2+ signals in mouse pancreatic acinar cells.
In the present study we have investigated cytosolic and mitochondrial Ca(2+) signals in isolated mouse pancreatic acinar cells double-loaded with the fluorescent probes fluo-3 and rhod-2. Stimulation of pancreatic acinar cells with 500 nm acetylcholine caused release of Ca(2+) from intracellular stores and produced cytosolic Ca(2+) signals in form of Ca(2+) waves propagating from the luminal to the basal cell pole. The increase in the cytosolic Ca(2+) concentration was followed by Ca(2+) uptake into mitochondria. Between onset of cytosolic and mitochondrial Ca(2+) signals there was a delay of 10.7 +/- 0.4 s. Ca(2+) uptake into mitochondria could be inhibited with Ruthenium Red and carbonyl cyanide m-chlorophenylhydrazone, whereas 2,5-di-tert-butylhydroquinone, which inhibits sarco(endo)plasmic reticulum Ca(2+) ATPases, did not prevent Ca(2+) accumulation in mitochondria. Carbonyl cyanide m-chlorophenylhydrazone-induced Ca(2+) release from mitochondria could only be observed after a preceding stimulation of the cell with a physiological agonist or by treatment with 2, 5-di-tert-butylhydroquinone, indicating that under resting conditions mitochondria do not contain releasable Ca(2+) ions. Analysis of the propagation rate of acetylcholine-induced Ca(2+) waves revealed that inhibition of mitochondrial Ca(2+) uptake did not accelerate spreading of cytosolic Ca(2+) signals. Our experiments indicate that in the early phase of secretagogue-induced Ca(2+) signals, mitochondria behave as passive Ca(2+)-buffering elements and do not actively suppress spreading of Ca(2+) signals in pancreatic acinar cells.
González
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Department of Physiology, University of the Saarland, D-66421 Homburg/Saar, Germany.
Schulz
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Schmid
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D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006873:Hydroquinones / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D010179:Pancreas / Q000166:cytology / Q000502:physiology*; D012430:Ruthenium Red / Q000494:pharmacology
D004791:Enzyme Inhibitors; D006873:Hydroquinones; D012430:Ruthenium Red; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; C018855:2-tert-butylhydroquinone; D000252:Calcium-Transporting ATPases; D000109:Acetylcholine; D002118:Calcium