title: Hypoxia/reoxygenation stimulates intracellular calcium oscillations in human aortic endothelial cells.
abstract: BACKGROUND
  We have previously shown that hydrogen peroxide stimulates endothelial [Ca(2+)](i) oscillations. This study was performed to determine whether posthypoxic reoxygenation stimulates [Ca(2+)](i) oscillations in vascular endothelial cells.
  
  
  RESULTS
  Hypoxia (glucose-free 95% N(2)/5% CO(2) bicarbonate buffer for 60 minutes) stimulated an increase in [Ca(2+)](i) from 111.9+/-7. 9 to 161.7+/-17.7 nmol/L (n=12, P:<0.01) in indo 1-loaded human aortic endothelial cells. On reoxygenation (glucose-containing 95% air/5% CO(2) bicarbonate buffer), 13 of 16 cells responded with repetitive [Ca(2+)](i) oscillations with an average amplitude of 570. 6+/-59.3 nmol/L, occurring at a mean interval of 0.28+/-0.04/min and persisting for >/=60 minutes. [Ca(2+)](i) oscillations were still observed in 4 of 7 cells studied in Ca(2+)-free buffer but did not occur when the intracellular Ca(2+) store was first depleted during hypoxia by either 1 micromol/L thapsigargin or by 10 mmol/L caffeine (n=6 for each). Reoxygenation-induced [Ca(2+)](i) oscillations were abolished by 10 micromol/L diphenyleneiodonium, an inhibitor of NAD(P)H oxidase (n=7), and by polyethylene glycol (PEG)-catalase (5000 U/mL, n=4) but were not prevented by inhibitors of xanthine oxidase (n=5), cyclooxygenase (n=4), nitric oxide synthase (n=5), the mitochondrial electron transport chain (n=4), or by PEG-superoxide dismutase (n=5).
  
  
  CONCLUSIONS
  Posthypoxic reoxygenation stimulates repetitive [Ca(2+)](i) oscillations that are dependent on Ca(2+) release from an intracellular pool and require extracellular Ca(2+) to be maintained. These oscillations may be initiated by NAD(P)H oxidase-derived hydrogen peroxide and may play a role in signal transduction during ischemia/reperfusion in vivo.
authors.affiliation: Department of Medicine, Division of Cardiology, Johns Hopkins Bayview Medical Center, Johns Hopkins University School of Medicine, Baltimore, MD 21224-2780, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Hu
authors.forename: R C
authors.initials: RC
authors.lastname: Ziegelstein
mesh_terms: D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019255:NADPH Oxidases; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010100:Oxygen / Q000378:metabolism* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D014475:Uncoupling Agents / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors
chemical_list: D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D014475:Uncoupling Agents; D012402:Rotenone; D006861:Hydrogen Peroxide; D019001:Nitric Oxide Synthase; D014969:Xanthine Oxidase; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D010100:Oxygen; D002118:Calcium