Thrombin-, bradykinin-, and arachidonic acid-induced Ca2+ signaling in Ehrlich ascites tumor cells.
Stimulation of single Ehrlich ascites tumor cells with agonists (bradykinin, thrombin) and with arachidonic acid (AA) induces increases in the free intracellular Ca2+ concentration ([Ca2+]i) in the presence and absence of extracellular Ca2+, measured using the Ca2+-sensitive probe fura 2. Sequential stimulation with two agonists elicits sequential increases in [Ca2+]i, unlike addition of the same agonist twice. Bradykinin and thrombin have additive effects on [Ca2+]i in Ca2+-free medium. The phosphoinositidase C inhibitor U-73122 inhibits the agonist-induced increases in [Ca2+]i, whereas ryanodine has no effect. Pretreatment of cells in Ca2+-free medium with thapsigargin abolishes the bradykinin-induced increase in [Ca2+]i but not the response to thrombin. The AA-induced response is not inhibited by U-73122 and cannot be mimicked by the inactive structural analog trifluoromethylarachidonyl ketone. Pretreatment of the cells with 50 microM AA (but not with 10 microM AA) abolishes the agonist-induced increase in [Ca2+]i. Thus bradykinin, thrombin, and AA induce increases in [Ca2+]i in Ehrlich cells due to Ca2+ entry and release from intracellular stores. Thrombin causes release of Ca2+ from an intracellular store that is insensitive to bradykinin and is not depleted by thapsigargin but is depleted by AA.
Jorgensen
N K
NK
Biochemical Department, August Krogh Institute, DK-2100 Copenhagen, Denmark.
Petersen
S F
SF
Hoffmann
E K
EK
D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism* / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D009994:Osmolar Concentration; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000187:drug effects; D011760:Pyrrolidinones / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D004791:Enzyme Inhibitors; D004963:Estrenes; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D019837:Ryanodine Receptor Calcium Release Channel; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D012433:Ryanodine; D016718:Arachidonic Acid; D019284:Thapsigargin; D010727:Phosphoric Diester Hydrolases; C021491:glycerophosphoinositol glycerophosphodiesterase; D013917:Thrombin; D001920:Bradykinin; D002118:Calcium