Objective To explore the impact of ischemic postconditioning on ischemia-reperfusion injury in isolatedelderly rat hearts and their relation with P-Akt. Methods A total of 30 healthy elderly SD rats (21-23 months old， male or female) with their body weight of 450-500 g were divided into 3 groups: control group， ischemia-reperfusion group， and postconditioning group， with 10 rats in each group. Coronary artery blood flow，myocardial infarction size， phosphorylatedAkt （p-Akt） expression， and changes in myocardium and mitochondria were detected. Results Coronary artery blood flow of the postconditioning group was significantly higher than that of the ischemia-reperfusion group （6.4±1.2 ml/min vs.3.1±1.2 ml/min， P＜0. 01）， and myocardial infarction size of the postconditioning group was significantly smaller thanthat of the ischemia-reperfusion group （35.0%±2.0% vs. 55.7%±3.6%， Plt;0. 05）. The expression of P-Akt was significantlyhigher， and myocardial fibers and mitochondria were preserved better in the postconditioning group than the ischemia-reperfusion group. Conclusion Ischemic postconditioning can protect isolated elderly rat hearts against ischemia-reperfusion injury， which may be related to P-Akt activation.
Objective To determine the protection effects and mechanisms for immature myocardium with limbs ischemic preconditioning (LIP). Methods Using the Langendorff perfusion apparatus to perfuse isolated hearts, we randomly divided 30 Japanese longeared white rabbits into 5 groups, each having 6 rabbits. For the I/R group，after the perfusion model was established, the isolated hearts underwent 15 min of perfusion with KH solution before working for another 15 min . Then perfusion was stopped to cause ischemia for 45 min before reperfusion for 15 min and working for another 30 min . For E1 group, the model was established by 3×LIP (double limbs obstructed for 5 min followed by 5 min reperfusion for 3 times) and then procedures of the I/R group were carried out. For E2 group, before procedures of the E1group were done, superoxide dismutase (SOD) was injected till LIP was completed. For E3 group, intravenous protein kinase C (PKC) polymyxin (PMB) was injected for 10 minutes before E1 procedures were repeated. For E4 group, intravenous mitochondrial ATPsensitive K+ channels (mitoKATP) blocker 5-hydroxydecanoate was injected for 10 min before E1 procedures were carried out. The left ventricular function recovery, myocardial water content (MWC), creatine kinase (CK) and lactate dehydrogenase (LDH) leakage, malondialdehyde (MDA) and ATP content, SOD activity and superoxygen negative ion (O2 ·-) content were tested. Results Left ventricular recovery in E1 group was better than other groups (Plt;0.05). ATP content and SOD activity in E1 group were also better than all other groups (Plt;0.05). MWC in E1 group was lower than other groups (Plt;0.05). MDA content, CK and LDH leakage in E1 group were also lower than other groups (Plt;0.05). There was no significant difference of the above indications among I/R,E2,E3 and E4 groups, while the difference of O2·- content in E1,E3 and E4 groups before and after preconditioning was significant. Conclusion LIP has obvious protective effects for immature myocardium and the mechanisms are probably through PKC stimulation and opening of mitoKATP.