| Objective: By establishing the model of myocardial ischemia-reperfusion injury in rats, we intend to observe the changes of ECG, changes of serum CK-MB, CK, LDH concentration, morphological changes of myocardial tissue and ultrastructural changes in the mitochondria of cardiac cells. Then, we aim to investigate the protective effect of the presence of myocardial ischemia distal limb treatment.Method: Healthy SD rats of either gender, aged 2 to 3 months and weighting 250 to 350 grams were enrolled in the study to establish the model of myocardial ischemia-reperfusion injury. All the rats were randomly divided into three groups with 10 in each group, namely Sham group, group of myocardial ischemia-reperfusion injury(I/R group) and group of myocardial ischemia-reperfusion injury and distal limb ischemia postconditioning(I/R + RLIPOC group, referred RLIPOC group).After thoracotomy, rats of I/R group and RLIPOC groups were ligated by 6-0 thread in anterior descending coronary artery(LAD). Sham group were without ligation. I/R group and RLIPOC groups were ligated in LAD to make left ventricular myocardial ischemia for 30 min, then LAD was opened to restore myocardial blood flow perfusion of 120 min. In RLIPOC group, at the time of myocardial ischemia for 15 min, the left legs of rats were bound for 10 min ischemia, then the blood flow perfusion of left leg was restored. During the whole experiment, the changes of heart rate(HR) of rats and Ⅱlead ECG were monitored continuously and the stages of ischemia and reperfusion arrhythmia occurrence and rate were recorded. Before the myocardial ischemia and at the time of 120 min reperfusion, blood specimens were extracted respectively in the internal jugular vein and the concentration of serum creatine kinase myocardial isoenzyme(CK-MB), creatine kinase(CK), and lactic acid deoxidizing enzyme(LDH) were detected. Rats’ hearts were removed at the end of 120 min reperfusion to observe myocardial tissue morphology by HE staining and pathology changes in myocardial ultrastructure of mitochondria within the cell were observed by TEM.Results:1.Compared with Sham group, the incidence rates of arrhythmia in the I/R group and RLIPOC was significantly increased at the initial term of the reperfusion and the arrhythmia score increased significantly. Compared with the I / R group, the number of arrhythmia in RLIPOC group reduced during reperfusion and the arrhythmia score was significantly decreased(3.44±0.53 VS 1.63±0.92,P<0.01). The difference was statistically significant.2. The serum CK-MB, CK, LDH concentration of the three groups showed no significant difference before ischemia(CK-MB: Sham group 200.19 ± 30.02U/L, I/R group 216.49 ± 15.92U/L, RLIPOC group 194.90 ± 46.33U/L; CK: Sham group 819.07 ± 177.02U/L, I/R group 788.22 ± 151.04U/L, RLIPOC group 746.36 ± 132.84U/L; LDH: Sham group 111.20 ± 9.36U/L, I / R group 120.20 ± 15.83U/L, RLIPOC group 146.25 ± 21.23U/L; P> 0.05). Compared with the Sham group, serum CK-MB, CK, LDH concentrations of the I/R and RLIPOC group were significantly increased after reperfusion 120min(CK-MB: Sham group 203.55 ± 32.25U/L, I/R group 1229.57 ± 92.0 3U/L, RLIPOC group610.17 ± 89.18U/L; CK: Sham group 789.68 ± 144.66U/L, I/R group 11600.67 ± 875.84U/L, RLIPOC group 5443.98 ± 821.97U/L; LDH: Sham group 119.00 ± 19.92U/L, I/R group 1039.43 ± 70.55U/L, RLIPOC group 665.83 ± 77.98U/L; P<0.05). Compared with the I/R group, serum CK-MB, CK, LDH levels of RLIPOC group were significantly reduced(P<0.05).3. Compared with Sham group, the myocardial tissue of I/R group showed regional necrosis of muscle fibers derangement, significant swelling of muscle fibers, muscle wire breakage dissolved. Besides, it showed interstitial edema, a large number of neutrophil infiltration and dilated blood vessels. In addition, myocardial cell volume increased significantly, showing vacuolar degeneration, nuclear condensation or fragmentation after 120 min cardiac reperfusion by HE staining. Compared with the I/R group, the muscle fibers were arranged in neat, muscle fibers mild swelled and muscle wire part of the fracture dissolved. Besides, it showed interstitial part of edema and neutrophil infiltration reduced. In addition, the volume of myocardial cell slightly increased, with few vacuolar degenerated and less nuclear karyopyknosis of the RLIPOC group. By observing the heart under TEM, it showed significant changes of the nucleus, rupture even shrinkage of nuclear membrane, chromatin condensation and distribution of clutter in I/R group. Besides, the disappearance of arcomere structure, muscle wire breakage and Z line thickening can be also seen. In addition, mitochondrial swelling and vacuolar degeneration were presented, with flocculent changes, loose crest and electron dense granules deposition. As for RLIPOC group, nuclear membrane integrity, relatively clear sarcomere structure of each zone, basic muscle filaments arranged in neat rules without obvious fracture can be seen. Besides, mild swelling of mitochondria with no vacuolation forming, change in homogeneous, crest of mitochondria turn to denser were presented.Conclusion: 1.RLIPOC reduce the incidence of ventricular arrhythmias and reduce myocardial I/R injury in rats within myocardial reperfusion period.2.RLIPOC reduce the concentration of rat’s CK-MB, CK, and LDH level during myocardial ischemia and reperfusion and reduce damage and necrosis of myocardial cell.3.RLIPOC reduce rat myocardial tissue infiltration of neutrophils, the damages of heart muscle fiber and the necrosis rate of the mitochondria. |
PDF Full Text Request