慢性血管紧张素II刺激对豚鼠心肌电生理的影响

Chronic angiotensin Ⅱ stimulation produces guinea-pig myocardial hypertrophy and its cardiac electrophysiology remodeling of research

目的观察慢性给予血管紧张素Ⅱ(AngⅡ)豚鼠心脏结构和功能的改变。方法 20只雄性成年豚鼠随机分成两组,AngⅡ组背部皮下手术置入预装AngⅡ渗透泵,经渗透泵持续释放AngⅡ1.2 mg/(kg·d),给药4周。对照组平行饲养。于第4周末对两组豚鼠行经胸二维M-型超声心动监测。并在用药前1天,用药1、2、3、4周末麻醉下测定心电图(ECG)的变化,4周后处死动物心脏称重并急性分离心室肌细胞,利用膜片钳技术记录动作电位(APD)及延迟整流钾电流快速成分(IKr)。结果对照组超声测得左室重量为(2.15±0.26)mg/g,AngⅡ组为(3.08±0.11)mg/g(P<0.01),超声测得心脏左室质量与称重测得心脏质量结果较一致。超声显示AngⅡ组LVPWTd、LVPWTs、IVSTd和IVSTs较对照组明显增大,表明心室明显增厚,EF、FS降低,说明心功能降低,AngⅡ组发生心肌肥厚且伴有心脏衰竭的发生。ECG记录显示矫正QT间期(QTc)呈时间依赖性延长。第2、3、4周末QTc由手术前(286.2±5.6)ms分别延长至(310.0±15.0)、(315.6±12.2)和(326.8±12.2)ms(P<0.01)。膜片钳记录结果显示APD50和APD90明显延长,对照组分别为(255.0±12.8)ms和(293.1±13.6)ms,AngⅡ组分别为(370.3±21.7)ms和(415.4±32.5)ms(P<0.01)。与对照组相比,AngⅡ组IKr的尾电流在-20^-60 mV电压范围内,均较对照组明显减少(P<0.01)。用Boltzmann方程拟合标准化的尾电流-电压关系曲线,对照组半数激活电压(V1/2)为(-20.9±2.6)mV,AngⅡ组为(-17.4±3.7)mV,显示AngⅡ对V1/2没有影响。结论缓慢长期给予AngⅡ可复制心肌肥厚动物模型,模型动物的心肌电生理发生明显改变,主要表现在ECG上QT间期延长和APD复极延长,与主要复极电流IKr功能下调有关。

【Objective】 To investigate the changes of cardiac structure and heart function in guinea pigs which induced by chronic Ang Ⅱ stimulating. 【Methods】 20 adult male guinea pigs were divided into two groups randomly： control group and Ang Ⅱ group. For Ang Ⅱ group, osmotic infusion pump was pre-loaded with Ang Ⅱ placed under the skin of guinea pigs on the back surgery, by which Ang Ⅱ 1.2 mg/（kg·d） has been released for 4 weeks. In control group, guinea pigs were feeded in parallel. At the end of 4th week,M-mode echocardiogram monitor would be done for the two groups. And the changes of ECG should be checked or tested on the day before of surgery and at the end of 1st w, 2nd w, 3rd w, 4th w. At the end of4 th w, all guinea pigs would be killed and weighed the hearts weight. Guinea pig ventricular cells were acute isolated. By patch-clamp technique APD50 and APD90 and IKr current were observed. 【Results】 The left ventricular weight of control group measured by echocardiogram was（2.15 ± 0.261 mg/g）, and Ang Ⅱ group was（3.08 ± 0.11 mg/g）（P〈 0.01）. Cardiac left ventricular mass measured by M-mode echocardiogram in Guinea pig heart is consistent with the results weighed. In addition, M-mode echocardiogram results display LVPWTd,LVPWTs, IVSTd and IVSTs of Ang Ⅱ group were significantly increased, which indicated that the cardiac ventricle was significantly hypertrophy. EF and FS were decreased, which indicated that heart function decreased, and cardiac hypertrophy associated with heart failure occurred in Ang Ⅱ group. On electrocardiogram QTc interval was time-dependently lengthen. At the end of 2nd w, 3rd w, 4th w, QTc were prolonged from the control values of（286.2 ± 5.6 ms） to（310.0 ± 15.0 ms）,（15.6 ± 12.2 ms）,（326.8 ± 12.2 ms） respectively（P〈 0.01）. Patch clamp results shown APD50 and APD90 significantly prolonged and the control values were（255.0 ± 12.8 ms） and（293.1 ± 13.6 ms） and Ang Ⅱ group were（370.3 ± 21.7 ms） and（415.4 ± 32.5 ms） respectively（P〈 0.01）. Compared with the control group, IKrtail current density of Ang Ⅱ group decreased significantly at-20 mV --60 mV（P 〈0.01, n =6）. Tail current-voltage relation curve fitting by Boltzmann equation,V1/2of control group was（-20.9 ± 2.6 mV）, Ang Ⅱ Group was（-17.4 ± 3.7 mV）, which indicated Ang Ⅱ did not affect V1/2significantly. 【Conclusion】 The animal models of cardiac hypertrophy can be prepared by slow long term given Ang Ⅱ, myocardial electrophysiology characteristic of animal models were dramatically reconstructed, it mainly reflected in APD and QT prolonged and this associated with major repolarization current IKr.