Characterization of intracellular calcium oscillations induced by extracellular nucleotides in HEp-2 cells.
The effect of extracellular nucleotides on the cytosolic calcium concentration of fluo-3-loaded HEp-2 cells was examined using confocal microscopy. Extracellular ATP and UTP at micromolar concentration induced cytosolic calcium oscillations in 42-66% of the cells. Oscillations were usually sinusoid and their frequency depended only slightly on agonist concentration. Oscillations developed in calcium-free medium but were diminished by depletion of intracellular calcium stores with thapsigargin, indicating periodic calcium release from internal stores. Inhibition of phospholipase C with U73122 prevented the development of oscillations, while ryanodine did not abolish the response to extracellular nucleotides. Activation of protein kinase C with 4beta-phorbol 12-myristate 13-acetate also prevented the development of oscillations. These results indicate that extracellular nucleotides induce periodic calcium release from inositol 1,4,5-trisphosphate-sensitive pools in HEp-2 cells and that the inhibitory effect of protein kinase C on the phosphatidylinositol signaling pathway can contribute to the development of intracellular calcium oscillations.
Department of Biophysics, University of Pécs, Faculty of Medicine, Hungary.
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Visegrády
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Grama
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Somogyi
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Lustyik
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000814:Aniline Compounds; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D018613:Microscopy, Confocal; D011493:Protein Kinase C / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014544:Uridine Triphosphate / Q000494:pharmacology*; D014966:Xanthenes
D000814:Aniline Compounds; D004791:Enzyme Inhibitors; D004963:Estrenes; D011760:Pyrrolidinones; D014966:Xanthenes; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D012433:Ryanodine; C059715:Fluo-3; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate; D014544:Uridine Triphosphate