Animal model of myocardial ischemia/reperfusion injury

All procedures involving experimental animals were performed following protocols approved by the Committee for Animal Research of Fourth Military Medical University and conformed to the Guide for the Care and Use of Laboratory Animals. Young (3 months) and aged (20 months) male Sprague-Dawley (SD) rats were subjected to myocardial ischemia/reperfusion (MI/R), as described previously [18]. Briefly, rats were anesthetized with pentobarbital sodium (50 mg/kg, i.p.) and ventilated on a Harvard rodent respirator via a tracheostomy. A midline sternotomy was performed, and the left anterior descending artery (LAD) was ligated with a 5-0 silk suture. Electrocardiograms confirmed ischemic repolarization changes (ST-segment elevation) during coronary occlusion. After 30 minutes of MI, the slipknot was released, and the myocardium was reperfused for 2 hours, 4 hours or 24 hours (for cardiac function, infarct size determination and echo-cardiography). Intravenous infusion of insulin was at 4 mL/kg (60 U/L) per hour beginning 5 minutes before reperfusion. Hemodynamics indexes were recorded for the entire procedure from multi-channel physiological signal acquisition processing system (PowerLab, AD Instruments) that was connected to pressure transducer.