抑制钙敏感受体对慢性心力衰竭大鼠室性心律失常易感性的影响

Effect of calcium-sensing receptor inhibition on the vulnerability of ventricular arrhythmia in a rat model of chronic heart failure

目的探讨抑制钙敏感受体（CaSR）对慢性心力衰竭（CHF）大鼠室性心律失常（VA）的影响。方法雄性SD大鼠48只，采用数字表法随机分为对照组、CHF组和干预组（n=16），分别给予生理盐水、异丙肾上腺素（ISO）及ISO＋CaSR特异性抑制剂（NPS2143）连续腹腔注射2周。完成药物注射2周后行超声心动图评价心功能。在整体心脏Langendorff灌流条件下行程控增频刺激，记录左心室前壁基底部（LAB）单相动作电位，评价动作电位时限（APD）电交替及VA的诱发阈值，并构建电整复性（APDR）曲线。急性分离大鼠心室细胞，采用钙荧光指示剂Fura-2AM进行孵育后记录各组心肌细胞钙瞬变（CaT）；Westernblot法检测左心室CaSR、三磷酸肌醇受体（IP3R）及蛋白激酶C（PKC）表达。结果与对照组相比，CHF组心室CaSR、IP3R及PKC表达量、90％动作电位复极时限（APD90）、APDR曲线最大斜率（Smax）及舒张期Ca^2＋水平均显著增加，差异有统计学意义（P〈0．05），而心肌细胞CaT幅度、APD电交替及VA的诱发阈值均显著减小，差异有统计学意义（P〈0．05）；与CHF组相比，干预组心室IP3R及PKC表达量、APD帅、APDR曲线s…及舒张期ca2＋水平均减少，差异有统计学意义（P〈0．05），而心肌细胞CaT幅度、APD电交替及vA的诱发阈值均显著增加，差异有统计学意义（P〈0．05）。CHF组和干预组心室CaSR表达量差异无统计学意义（P〉0．05）。结论抑制CaSR可降低CHF大鼠VA易感性，CaSR可作为CHF后VA潜在干预靶点。

Objective To investigate the effect of calcium-sensing receptor （ CaSR ） inhibition on the vulnerability of ventricular arrhythmia （ VA ） in a rat model of chronic heart failure （ CHF ） .Methods A total of 48 male rats were randomized to receive saline （ control group ）,isoproterenol （ ISO ）（ CHF group ） and ISO ＋ NPS2143 （ a specific inhibitor of CaSR ） （ treatment group ） for 2 weeks. Two weeks later, the cardiac function of three groups was assessed by eehocardiography. In the whole Langendorff-perfused hearts, the monophasic action potential was recorded from left anterior basic ventricle. The programmed electrical stimulation was used to determine the thresholds of action potential duration （ APD ） alternans and VA and constructed the APD restitution （ APDR ） curves in each group. The calcium ixansient （ CaT ） was measured by loading with fura-2 AM in isolated cardiomyoeytes. The expression of CaSR, inositol 1,4, 5-trisphosphate receptors （ IP3R ） and protein kinase C （ PKC ）was detected by western-blotting. Results Compared with the control group, the protein expression of CaSR, IP3R and PKC, APDg0, the maximal slope （ Smax ） of APDR curve and the diastolic intercellular C2＋ level were significantly increased （ all P〈0.05 ）, while the CaT amplitude and the APD alternans and VA thresholds were markedly reduced in the CHF group（ all P〈0.05 ）. Additionally, compared with the CHF group, the protein expression of IP3R and PKC, APDg0, the Smax of APDR curve and the diastolic inteellular 2＋Ca level were significantly decreased （ all P〈0.05 ）, while the CaT amplitude and the APD alternmls and VA thresholds were markedly increased in the treatment group （ all P〈0.05 ）. There was no signifieant difference in the CaSR expression between CHF and treatment groups. Conclusion Inhibition of CaSR could reduce the vulnerability of VA in rats with CHF, which could be file potential therapeutic target of CHF associated VA.