Limb Remote Ischemic Perconditioning Protects Heart Against Ischemia/ Reperfusion Injury In Rats

Aim: The cardiac ischemic preconditioning (IPC) and ischemic postconditining (PostC) have significant cardiac protection against ischemia/reperfusion injury. Both of ischemia conditioning share same mechanism to induce the cardioprotection, such as adenosine, bradykinin, opiate and opiate receptors, and ATP-sensitive potassium channel. IPC and PostC in remote organ, such as limbs, kidney and mesentery, can also induce cardiac protection effectively, which are called as remote ischemic preconditioning (RIPC)and remote ischemic postconditioning (RPostC), respectively. A recent study in which a repeated brief ischemia/reperfusion in low limbs of pig conducted with cardiac ischemia simultaneously showed a cardiac protection. The phenomenon was called as remote ischemic perconditioning ( RPerC ) and found to be related with opening of ATP-sensitive potassium channel. Up to now, we don't know whether the limb RPerC has the same cardiac protection in rat and whether opiate as well as opiate receptors are involved in the cardiac protection induced by limb RPerC. The aim of present study was to explore the cardioprotection elicited by the limb RPerC in rat and the underlying mechanism.Method: Healthy adult male Sprague-Dawley rats were divided randomly into five groups. Ischemia/reperfusion group (I/R), Pre-conditioning group (Pre-C), Per-conditioning group (Per-C), Naloxone group (Nal) and Glibenclamide group (Gli). Rat was anaesthetized with pentobarbital sodium and trachea intubation for artificial ventilation. The left femoral artery was cannulated for measurement of blood pressure (BP), including systolic arterial pressure(SAP)and diastolic arterial pressure(DAP). The right femoral artery was cannulated for conditioning and right femoral vein was cannulated for drugs administration. A cannula filled with calparine saline was inserted slowly into left ventricle through right carotid artery to record left ventricular peak pressure (LVSP), the maximal rate of rise and descent of left ventricular pressure (±LVPdP/dt max). Needle electrode was inserted limbs subcutaneously and standard lead II ECG was recorded to monitor the heart rate (HR) and arrhythmia. The chest was open and the heart was exposed. The left anterior descending coronary artery (LADCA) was ligated (ischemia) for 30 minutes and reopened (reperfusion) for 180 minutes in I/R group rats. Preconditioning was achieved by 5-min ligation of right femoral artery with 1-min reopen for three times just before LADCA occlusion in Pre-C group rats. Perconditioning was achieved by 5-min ligation of right femoral artery with 1-min reopen for three times simultaneously with LADCA occlusion in Per-C group rats. For Nal and Gli group rats, naloxone, an opiate receptor antagonist, and glibenclamide, an ATP sensitive potassium channel blocker, were used injected intravenously 5-minute before preconditioning, respectively. Staining was used to measure heart infarction after cardiac ischemia/reperfusion.Result: 1. The LVSP and±LVPdP/dt max were reduced during myocardial ischemia. LVSP, +LVdP/dt max and -LVdP/dt max in I/R rats were decreased by 33.5%, 39.3% and 32.6%, respectively. LVSP, +LVdP/dt max and -LVdP/dt max in Pre-C rats were decreased by 16.1%, 13.2% and 19.8%, respectively.。LVSP, +LVdP/dt max and -LVdP/dt max in Per-C rats were decreased by 20.2%, 15.8% and 14.0%, respectively. LVSP, +LVdP/dt max and -LVdP/dt max in Nal rats were decreased by 32.2%, 39.9% and 44.2%, trspectively. LVSP, +LVdP/dt max and -LVdP/dt max in Gli rats were decreased by 33.9%, 56.6% and 47.1%, respectively. The change of above parameters in Pre-C and Per-C rats were significantly smaller than that in I / R, Nal and Gli rats (P <0.05-0.01). During myocardial reperfusion, the hemodynamic and cardiac function parameters were gradually restored. Compared with the baseline, LVSP, +LVdP/dt max and -LVdP/dt max were recovered to 63.5%, 58.7% and 56.9% in I / R rats, 99.9%, 96.7% and 101.6% in Pre-C rats, 86.1%, 85.6% and 84.2% in Per-C rats, 72.0%, 56.3% and 53.7% in Nal rats, and 70.9%, 47.2% and 51.6% in Gli rats, respectively. The recover of above parameters in Pre-C and Per-C rats was much better than those in I / R, Nal and Gli rats (P <0.05-0.01). 2. The infarct area (IA) expressed as ratio of infarct area (IA) to area at risk(AAR) in Pre-C and Per-C group rats were 12.2% and 11.5%, respectively, significantly less than 42.0% in I / R rats, 31.4% in Nal rats, and 45.6% in Gli rats (P <0.05-0.01). 3. The ischemic arrhythmia scores in Pre-C and Per-C rats during myocardial ischemia were 1.5 and 1.4, respectively, significantly less than those in I / R, Nal, and Gli rats (P <0.05-0.01). The reperfusion arrhythmia scores in Pre-C and Per-C rats during reperfusion were 1.6 and 2.0, respectively, significantly smaller than those in I / R, Nal and Gli rats (P <0.05-0.01).Conclusion: The limb remote ischemic perconditioning has a cardiac protection on heart against ischemia/ reperfusion injury in rats, manifesting as abatement of inhibition of ventricular function induced by myocardial ischemia/ reperfusion, reduction of myocardial infarction area, and anti-arrhythmia, which might be accomplished via activation of opioid receptor and open of ATP-sensitive potassium channel.