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The Effect of Ischemic Preconditioning on Myocardial Ischemic Reperfusion of Elderly Rats

Objective To investigate the effect of ischemic preconditioning(IPC) on myocardial ischemic reperfusion injury(I/R) of elderly rats. Methods Fiftysix Wistar rats, of which there were 28 aged from 21-23months(elderly rat) and 28 aged from 4-5months(young rat), were used to build isolated heart perfusion Langendorff model. The rats were divided into 7 groups with random number table（8 in each group）: adult control group, adult I/R group, adult IPC group, elderly control group, elderly I/R group, elderly IPC group and elderly enhanced IPC group. The control group underwent a 90-min perfusion without any intervention; the I/R group underwent a 30-min equilibration period, then a 30-min ischemia and a 30-min reperfusion; the IPC group underwent a 10-min equilibration period, then a 5-min ischemia for twice and a 5-min reperfusion, after that a 30-min ischemia and [CM(158-3mm]a 30-min reperfusion; the enhanced IPC group underwent a 10-min equilibration period, then a 5-min ischemia for 4-times and a 5-min reperfusion, after that a 30-min ischemia and a 30-min reperfusion. The recovery rates of cardiac output(CO), left ventricular developed pressure (LVDP), the maximum rising and descending rate of left ventricular pressure (±dp/dtmax) after a 30-min reperfusion were compared among groups. The activity of creatine kinase (CK) in coronary outflow, the level of malonyldialdehyde (MDA) and superoxide dismutase (SOD) before ischemia and after a 30min reperfusion were detected. The myocardial infarction areas were compared among groups. Results After a 30min reperfusion, compared with adult I/R group, in adult IPC group CK reduced significantly(89.48±18.72 U/L vs. 115.76±16.72 U/L，q=6.061，Plt;0.01)，the level of MDA decreased significantly（9.53±3.44 nmol/ml vs. 16.84±2.29 nmol/ml，q=7.732，Plt;0.01)，the level of SOD increased significantly（584.7±122.62 U/ml vs. 429.46±85.24 U/ml，q=4.754，Plt;0.01)，the recovery rates of CO,LVDP,+dp/dtmax and -dp/dtmax increased ignificantly(78.69%±9.68% vs. 65.10%±8.63%，83.61%±8.46% vs. 67.23±8.68%，81.68±8.68% vs. 67.89%±6.89%，89.79%±7.78% vs. 66.79%±8.46%，Plt;0.01), the myocardial infarction areas reduced significantly (5.25%±4.33% vs. 14.75%±8.02%,q=7.458，Plt;0.01)。There was no statistical significance between elderly IPC group and elderly I/R group in the above indexes（Pgt;0.05）.However, There was statistical significances between elderly enhanced IPC group and I/R group. CK reduced significantly (88.60±28.32 U/L vs. 105.76±9.64 U/L，q=5.620，Plt;0.01)，the level of MDA decreased significantly（8.38±3.36 nmol/ml vs. 16.80±3.06 nmol/ml，q=7.500，Plt;0.01)，the level of SOD increased significantly（558.87±78.66 U/ml vs. 433.75±86.65 U/ml，q=7.335，Plt;0.01)，the recovery rates of CO,LVDP,+dp/dtmax and -dp/dtmax increased significantly (77.99%±10.02% vs. 66.26%±9.78%，85.59%±6.67% vs. 73.90%±6.66%，83.87%±9.98% vs. 68.90%±8.68%，86.01%±766% vs. 70.39%±7.98%，Plt;0.01)， the myocardial infarction areas reduced significantly (795%±6.32% vs. 1568%±10.36%,q=8.680， Plt;0.01). 〖WTHZ〗Conclusion The protective effect of IPC on I/R elderly rat hearts has weakened. The enhanced IPC is able to regain the protective effect of IPC on elderly rat hearts.