title: Involvement of superoxide and nitric oxide in the genesis of reperfusion arrhythmias in rats.
abstract: To assess the role of reactive oxygen species and nitric oxide (NO) in the genesis of reperfusion-induced arrhythmias, the effects of reactive oxygen species scavengers and NO synthase inhibitors on the incidence of ventricular fibrillation and irreversible ventricular fibrillation (mortality) were examined. Hearts of anesthetized rats were subjected to 4 min regional ischemia followed by 4 min reperfusion. The animals were treated i.v. with superoxide dismutase, a O2- scavenger, catalase, a H2O2 scavenger, dimethylthiourea, a .OH scavenger, or NG-nitro-L-arginine methyl ester (L-NAME) and NG-nitro-L-arginine (L-NNA), NO synthase inhibitors. Superoxide dismutase (430 and 4300 U/kg/min) reduced the mortality from 93% to 43% and 57%, respectively, whereas treatment with catalase or dimethylthiourea did not affect these arrhythmias. L-NAME (0.1 and 0.3 mg/kg/min) reduced the mortality from 93% to 50% and 43%, respectively. L-NNA (0.3 mg/kg/min) reduced the mortality from 93% to 50%. This reduction by the NO synthase inhibitors was abolished by administration of L-Arg. However, L-Arg blocked neither a small increase in systolic blood pressure nor a decrease in heart rate elicited by the NO synthase inhibitors. The combinated treatment of superoxide dismutase (4300 U/kg/min) with L-NAME (0.3 mg/kg/min) reduced the mortality from 93% to 7%. These results suggest that the genesis of reperfusion-induced arrhythmias observed in this model may be in part due to O2- and NO.
authors.affiliation: Department of Pharmacology, Tokyo University of Pharmacy and Life Science, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Ohoi
authors.forename: S
authors.initials: S
authors.lastname: Takeo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002374:Catalase / Q000494:pharmacology; D003451:Cryoprotective Agents / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology; D014693:Ventricular Fibrillation / Q000209:etiology / Q000401:mortality / Q000517:prevention & control*
chemical_list: D003451:Cryoprotective Agents; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D019335:Nitroarginine; D009569:Nitric Oxide; C038983:1,3-dimethylthiourea; D002374:Catalase; D013890:Thiourea; D019331:NG-Nitroarginine Methyl Ester; D004121:Dimethyl Sulfoxide