Hypotonic stress-induced dual Ca(2+) responses in bovine aortic endothelial cells.
We have investigated the effects of hypotonic stress on intracellular calcium concentration ([Ca(2+)](i)) in bovine aortic endothelial cells. Reducing extracellular osmolarity by 5% to 40% elicited a steep Ca(2+) transient both in normal Krebs and Ca(2+)-free solutions. The hypotonic stress-induced Ca(2+) transient was inhibited by phospholipase C inhibitors (neomycin and U-73122), a P(2)-receptor antagonist (suramin), and an ATP-hydrolyzing enzyme (apyrase), suggesting that the hypotonic stress-induced Ca(2+) transient is mediated by ATP. A luciferin-luciferase assay confirmed that 40% hypotonic stress released 91.0 amol/cell of ATP in 10 min. When the hypotonic stress-induced fast Ca(2+) transient was inhibited by neomycin, suramin, or apyrase, a gradual [Ca(2+)](i) increase was observed instead. This hypotonic stress-induced gradual [Ca(2+)](i) increase was inhibited by a phospholipase A(2) inhibitor, 4-bromophenacyl bromide. Furthermore, exogenously applied arachidonic acid induced a gradual [Ca(2+)](i) increase with an ED(50) of 13.3 microM. These observations indicate that hypotonic stress induces a dual Ca(2+) response in bovine aortic endothelial cells, i.e., an ATP-mediated fast Ca(2+) transient and an arachidonic acid-mediated gradual Ca(2+) increase, the former being the predominant response in normal conditions.
Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan. moike@pharmaco.med.kyushu-u.ac.jp
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Oike
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Kimura
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Koyama
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Yoshikawa
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001013:Aorta, Thoracic; D001081:Apyrase / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D003470:Culture Media; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004963:Estrenes / Q000494:pharmacology; D007038:Hypotonic Solutions; D007700:Kinetics; D009355:Neomycin / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D013498:Suramin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
D003470:Culture Media; D004963:Estrenes; D007038:Hypotonic Solutions; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D016718:Arachidonic Acid; D013498:Suramin; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D001081:Apyrase; D009355:Neomycin; D002118:Calcium