缺血后适应对糖尿病大鼠再灌注心肌的保护作用及其与P—Akt的关系

The protective effect of myocardial ischemic postconditioning on isolated diabetic rat heart and its relation with P-Akt- WANG Bo

目的探讨缺血后适应对糖尿病大鼠离体心脏缺血再灌注损伤的影响及其信号机制。方法2周龄健康sD大鼠60只，雌雄不拘，体重250～300g，随机分为6组：空白对照组（N组）；缺血再灌注组（IR组）；缺血后适应组（Post组）；糖尿病大鼠后适应组（Dpost组）；糖尿病大鼠缺血再灌注组（DIR组）；糖尿病大鼠空白组（DN组）。将链脲酶素（STZ，美国Sigma公司）按65nag／kg经大鼠腹腔注射，48h后断尾法连续两次测血糖≥16．65mmol／L，并出现多饮、多食、多尿、体重减轻，脱毛等表现确定糖尿病模型成功。糖尿病模型制作成功后建立离体心脏Langendorff灌注模型，观测心脏冠状动脉灌流量、心肌梗死范围，免疫印迹（westernblot）对P—Akt测定、电镜下观察心肌和线粒体改变。结果糖尿病大鼠血糖浓度平均为（23．15±2．16）mmol／L，非糖尿病大鼠为（4．16±0．31）mmol／L。两组大鼠血糖浓度差异有统计学意义（P〈0．01）。缺血后适应组（Post组、DPost组）较缺血再灌注组（IR组、DIR组）冠状动脉流量（ml／min）明显增加（6．54±1．2、5．6±1．0对3．4±1．0、2．0±1．3），心肌梗死范围（％）明显减少（25．2±2．1、34．2±3．6对47．5±3．5、65．2±4．5），P—Akt的表达明显增强，心肌纤维和线粒体的完整程度明显较好。结论缺血后适应在糖尿病大鼠离体心脏具有显著的保护作用，这一作用可能与Akt激活有关。

Objective This study describes the protective effect of myocardial ischemic postconditioning on ischemic- reperfused myocardium （ I/ R） of diabetic rat and its Signaling mechanism. Methods Healthy SD rats weighing 250-300g were divided into 6 groups ： （ 1 ） Blank control ; （ 2 ） Ischemia-reperfusion ; （ 3 ） Post conditioning ; （ 4 ） Diabetic postconditioning; （5）Diabetic isehemia-reperfusion; （6） Diabetic blank control group. Ten rats in each group were randomly selected. Introduction of diabetic rat model： 65 mg/kg STZ was injected into the intraperitoneal cavity, until 2 consecutive blood glucose measurements ≥ 16.65 mmoL/L were reached after 48h. The diabetic model was successful when rats had following symptoms, such as more drinking, more eating, polyuria, weight loss and epilation. Langeudorff isolated rat heart perfusion was used for the experiment. Following parameters were measured and compared ： Coronary perfusion flow, myocardial infarct size, western blot for measurement of P-Akt, changes in myocardimn and mitochondrian observed by Electron microscopy. Results Blood glucose concentration in diabetic group was （23. 15 ± 2. 16 ） mmol/L and （4.16± 0.31 ） mmoL/L in non-diabetic group. There was a significant difference （P 〈 0. 01 ） between the two groups. There were more coronary flow in post-conditioning groups（ Post group and Dpost group）than ischemia-repeffusion groups （IR group and DIR group） （6.5 ± 1.2,5.6 ±1.0 vs. 3.4 ± 1.0,2.0 ±1.3 ）. The myocardial infarction size was smaller in post-conditioning groups than in ischemia-reperfusion groups （25.2 ± 2.1,34.2±3.6 vs. 47.5± 3.5,65.2± 4.5 ）. There was more expression of P-Akt and the myocardial fibers and mitoehondrian in post-conditioning groups were better preserved. Conclusion Postconditioning has protective effects in diabetic rat hearts. The mechanism may be associated with Akt activation.