Cardioprotective effect of Thymoquinone: A constituent of Nigella sativa L., against myocardial ischemia/reperfusion injury and ventricular arrhythmias in anaesthetized rats.

Reperfusion of the ischemic myocardium causes the myocardial injury and life-threatening ventricular arrhythmias in human. This study aimed to investigate the effects of thymoquinone (TQ) on myocardial ischemia/reperfusion (I/R) injury and ischemia- and reperfusion-induced ventricular arrhythmias in anaesthetized rats. Adult male Wistar albino rats were divided into two groups, each containing a control and TQ-treated subgroups. In group I, the myocardial infarct size was determined by triphenyl tetrazolium chloride staining following 2-h reperfusion preceded by 30 min of ischemia. In group II, a 6-min myocardial ischemia was followed by a 10-min reperfusion. TQ-treated subgroups were treated with TQ (10 mg/100 μl/kg, i.p.) and the control subgroups were treated with the vehicle (100 μl/kg, i.p.) 20 min prior to the ischemic period. Ischemia was induced by ligating the left main coronary artery, followed by reperfusion. TQ treatment reduced the infarct size (15 ± 4% versus 69 ± 6%, P<0.01). Pretreatment with TQ decreased arrhythmia scores, as well as the incidence of ventricular tachycardia and the incidence of ventricular fibrillation during the reperfusion period (arrhythmia scores: 1.4 ± 0.3 versus 4.4 ± 0.3, P<0.01). These results suggest that TQ confers protection against myocardial I/R injury and suppresses reperfusion-induced arrhythmias.