Mechanism of the protective effects of noninvasive limbs preconditioning on myocardial ischemia-reperfusion injury

BACKGROUND: This study aimed at assessing the effect of noninvasive limb preconditioning on myocardial infarct size, and determining whether nitric oxide and neurogenic pathway play an important role in the mechanism of acute remote ischemic preconditioning (IPC). METHODS: Forty Wistar rats were randomly divided into four experimental groups. In Group I, the rats underwent 30-minute occlusion of the left anterior descending coronary artery, and 120-minute reperfusion. In Group PL, the rats underwent four cycles of 5-minute occlusion and reperfusion of both hind limbs using a tourniquet before the experiment was continued as in Group I. In Group PL-N and Group PL-H, we administered L-nitro-arginine methyl ester (L-NAME) 10 mg/kg or hexamethonium chloride 20 mg/kg intravenously, 10 minutes before IPC. Infarct size as a percentage of the area at risk was determined by triphenyltetrazolium chloride staining. RESULTS: There were no statistically significant differences in mean arterial pressure and heart rate among these groups at any time point during the experiment (P>0.05). The myocardial infarct size (IS) was decreased significantly in Group PL and Group PL-H compared with Group I, and the IS/AAR was 34.5%+/-7.6%, 35.9%+/-8.6% and 58.5%+/-8.5%, respectively (P< 0.05). The IS/AAR was 49.1%+/- 6.5% in Group PL-N, and there was no significant difference compared with Group I (P>0.05). CONCLUSIONS: Noninvasive limb IPC is effective in protecting the myocardium from ischemia reperfusion injury. Nitric oxide plays an important role in the mechanism of acute remote IPC, in which the neurogenic pathway is not involved.