title: Hypoxic reperfusion of the ischemic heart and oxygen radical generation.
abstract: Postischemic myocardial contractile dysfunction is in part mediated by the burst of reactive oxygen species (ROS), which occurs with the reintroduction of oxygen. We hypothesized that tissue oxygen tension modulates this ROS burst at reperfusion. After 20 min of global ischemia, isolated rat hearts were reperfused with temperature-controlled (37.4 degrees C) Krebs-Henseleit buffer saturated with one of three different O2 concentrations (95, 20, or 2%) for the first 5 min of reperfusion and then changed to 95% O2. Additional hearts were loaded with 1) allopurinol (1 mM), a xanthine oxidase inhibitor, 2) diphenyleneiodonium (DPI; 1 microM), an NAD(P)H oxidase inhibitor, or 3) Tiron (10 mM), a superoxide scavenger, and were then reperfused with either 95 or 2% O2 for the first 5 min. ROS production and tissue oxygen tension were quantitated using electron paramagnetic resonance spectroscopy. Tissue oxygen tension was significantly higher in the 95% O2 group. However, the largest radical burst occurred in the 2% O2 reperfusion group (P < 0.001). Recovery of left ventricular (LV) contractile function and aconitase activity during reperfusion were inversely related to the burst of radical production and were significantly higher in hearts initially reperfused with 95% O2 (P < 0.001). Allopurinol, DPI, and Tiron reduced the burst of radical formation in the 2% O2 reperfusion groups (P < 0.05). Hypoxic reperfusion generates an increased ROS burst originating from multiple pathways. Recovery of LV function during reperfusion is inversely related to this oxygen radical burst, highlighting the importance of myocardial oxygen tension during initial reperfusion.
authors.affiliation: Dept. of Emergency Medicine, The Ohio State Univ., 146 Means Hall, 1654 Upham Dr., Columbus, OH 43210, USA. angelos.1@osu.edu
authors.forename: Mark G
authors.initials: MG
authors.lastname: Angelos
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Kutala
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Torres
authors.forename: Guanglong
authors.initials: G
authors.lastname: He
authors.forename: Jason D
authors.initials: JD
authors.lastname: Stoner
authors.forename: Marwan
authors.initials: M
authors.lastname: Mohammad
authors.forename: Periannan
authors.initials: P
authors.lastname: Kuppusamy
mesh_terms: D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000154:Aconitate Hydratase / Q000378:metabolism; D000493:Allopurinol / Q000494:pharmacology; D000818:Animals; D003497:Cyclic N-Oxides / Q000378:metabolism; D000860:Hypoxia / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D015425:Myocardial Reperfusion / Q000379:methods; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology*; D009861:Onium Compounds / Q000494:pharmacology; D010100:Oxygen / Q000008:administration & dosage; D010313:Partial Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: D003497:Cyclic N-Oxides; D009861:Onium Compounds; D017382:Reactive Oxygen Species; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D000493:Allopurinol; C007517:diphenyleneiodonium; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D000154:Aconitate Hydratase; D010100:Oxygen