Objective: To assess whether myocardial fibrosis affects the protective efficiency of ischemic preconditioning (IPC) against myocardial ischemia/reperfusion injury (MIRI) in type 2 diabetic rats. Methods: Type 2 diabetic rat model was established. Fifty-four normal and 54 diabetic spragus-dawley (SD) rats were equally divided into 6 groups (n=18) using the random number table method: (1) Control group (C group); (2) Ischemia reperfusion injury (IRI) control group (IRI group); (3) IPC group; (4) Diabetic control group (DC group); (5) Diabetic IRI group (DIRI group); (6) Diabetic IPC group (DIPC group). After the reperfusion, blood samples were obtained for measuring serum concentrations of creatine kinase-MB (CK-MB) and cardiac troponin I (cTnI) using enzyme-linked immunosorbent assay (ELISA). The myocardial infarction size (IS) was assessed by double staining method with Evan's blue and Triphenyl tetrazolium chloride (TTC), and the myocardial collagen volume fraction (CVF) and perivascular collagen area (PVCA) were assessed by Masson staining. Results: A stable and effective rat model with long-term diabetes was established in the current study. Compared with the normal rat groups, the CVF and PVCA significantly increased (all P<0.05) in the diabetic rat groups. The levels of CK-MB, cTnI and IS in the IPC group were (6.6±0.8) ng/ml, (0.5±0.1) ng/ml and (25.1±4.7) %, which showed significant decrease compared with (12.3±1.1) ng/ml, (1.2±0.3) ng/ml and (52.3±8.1) % in IRI group (all P<0.05). Among the diabetic rat groups, the CK-MB and cTnI levels in DIPC group were (11.5±0.9) and (1.1±0.1) ng/ml, apparently lower than the levels of (16.6±2.2) and (1.4±0.3) ng/ml in the DIRI group (both P<0.05). Compared with the IPC group, the IS, CK-MB and cTnI levels significantly increased in the DIPC group (all P<0.05). Conclusion: Myocardial fibrosis exists in rats with long-term type 2 diabetes, which weakens the protective effect of IPC on diabetes MIRI.
目的： 探讨2型糖尿病大鼠缺血预处理（IPC）对心肌缺血再灌注损伤（MIRI）的保护作用是否受到糖尿病心肌纤维化的影响。 方法： 建立2型糖尿病大鼠模型，采用随机数字表法将54只正常大鼠和54只糖尿病大鼠各分成3组（n=18）：（1）空白对照组（C组）；（2）缺血再灌注损伤（IRI）对照组（IRI组）；（3）IPC组；（4）糖尿病空白对照组（DC组）；（5）糖尿病IRI对照组（DIRI组）；（6）糖尿病IPC组（DIPC组）。再灌注结束时采集各组大鼠静脉血，采用酶联免疫法（ELISA）检测血清肌酸激酶心肌型同工酶（CK-MB）和心肌肌钙蛋白I（cTnI）水平；采用Evan′s蓝和氯化三苯基四氮唑（TTC）双染法测定心肌梗死面积（IS）；采用Masson染色计算血管周围纤维化指数（PVCA）和心肌组织胶原容积分数（CVF）。 结果： 本研究建立了稳定有效的长病程2型糖尿病大鼠模型；和正常组大鼠相比，糖尿病组大鼠相同处理组左心室心肌组织CVF和PVCA均显著升高（均P<0.05）。正常组大鼠组内比较，IRI组CK-MB、cTnI水平和IS分别为（12.3±1.1）ng/ml、（1.2±0.3）ng/ml、（52.3±8.1）%，IPC组分别为（6.6±0.8）ng/ml、（0.5±0.1）ng/ml、（25.1±4.7）%，明显降低（均P<0.05）。糖尿病组大鼠组内比较，DIRI组CK-MB、cTnI水平分别为（16.6±2.2）、（1.4±0.3）ng/ml，DIPC组分别为（11.5±0.9）、（1.1±0.1）ng/ml，明显降低（均P<0.05）。与IPC组相比，DIPC组cTnI、CK-MB浓度和IS均明显升高（均P<0.05）。 结论： 长病程的2型糖尿病大鼠存在心肌纤维化，这种心肌纤维化减弱IPC对糖尿病MIRI的保护作用。.