Localization of cytoplasmic free calcium ions in PC12 cells with varicose fibers.
Differentiated PC12 cells with varicose fibers were used as a model of sympathetic neurons to demonstrate the intracellular localization of cytoplasmic free calcium ions. Changes in the concentration of cytoplasmic free calcium ions were analyzed at individual varicosities upon stimulation with acetylcholine by laser scanning confocal microscopy. Transient increases in cytoplasmic free calcium ion concentration were localized in the varicosities and recognized in both the absence and presence of extracellular Ca2+. Immunocytochemical analysis of intracellular calcium channels, 1, 4, 5-trisphosphate receptors and ryanodine receptors, by electron microscopy demonstrated that immunoreactive sites were mainly localized in large dense core vesicles in the varicosities and neurites. These results suggest that the exocytosis of large dense core vesicles is regulated by an increase in cytoplasmic free calcium ion concentration from an intracellular Ca2+ store.
Pharmaceutical Frontier Research Laboratories, Japan Tobacco Inc., Yokohama.
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Nakanishi
J
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Ichikawa
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Y
Endo
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000032:analysis*; D015220:Calcium Channels / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D007424:Intracellular Fluid; D007477:Ions; D016716:PC12 Cells; D051381:Rats
D015220:Calcium Channels; D007477:Ions; D000109:Acetylcholine; D002118:Calcium