短时刺激对心力衰竭心室肌电生理特性及钠钙交换体的影响

观察短时刺激对阿霉素心力衰竭 (简称心衰 )模型心室肌的电生理特性的影响 ,并研究钠钙交换体在其中的作用。 2 4只纯种日本大耳白兔随机分为对照组和阿霉素心衰组。心衰模型通过耳缘静脉每周注射一次 0 .2 %的阿霉素 ( 2mg/kg) ,持续 8周获得 ;对照组每周注射生理盐水 ( 2ml/kg)持续 8周。从第 10周开始进行实验 ,经兔耳缘静脉推注阿托品 ( 0 .0 4mg/kg) ,美多心安 ( 0 .2mg/kg)阻断神经支配。于心房快速刺激 30min前后 ,应用心脏电刺激及单相动作电位 (MAP)记录技术测定心电生理参数。左心室心肌组织钠钙交换体的蛋白量用免疫印迹方法定量。结果 :快速刺激后 ,心衰组和对照组心室肌的 90 %MAP时程 (MAPD90 )分别延长 14.1± 8.8ms和 8.7± 5 .6ms(P <0 .0 1) ,心室有效不应期 (ERP)分别延长 17.8± 8.4ms和 11.3± 6 .1ms(P <0 .0 1)。钠钙交换体的蛋白量没有明显的差异 (P >0 .0 5 )。结论 :短时快速刺激可引起阿霉素兔心衰模型心室肌的电生理特性发生改变 ,钠钙交换体的表达没有明显的改变。

Na+-Ca2+ Exchanger Expression and Its Role in the Alteration of Myocardial Electrophysiological Characters due to Short-Term Pacing in Heart Failure.

The goal of this study was to determine whether there was enhanced Na +-Ca 2+ exchanger (NCX) expression that might contribute to the alteration of myocardial electrophysiological characters due to short-term pacing in heart failure.Ten Japanese white rabbits received an injected of doxorubicin (2 mg/kg i.v.) once a week for 8 weeks.Fourteen rabbits were similarly injected with saline as control.Ten weeks after the first injection,the monophasic action potential duration (MAPD) and effective refractory period (ERP) were measured (S 1S 1 rate=260 ppm) at four sites (right ventricular outflow tract,RVOT;right ventricular apex,RVA;left ventricular outflow tract,LVOT;left ventricular apex,LVA) with atropine and metopronol pretreated.Then the right atria was paced at a rate of 260 ppm with 1∶1 conduction for 30 minutes,after pacing,the MAPD and ERP was measured repeatedly.The NCX protein (120 kd) was quantitated by western-blot analysis.Results:The MAPD 90 and ERP significantly increased after pacing in both groups,but ΔMAPD 90 and ΔERP in doxorubicin group was significantly more than those in control group,respectively 14.1±8.8 ms versus 8.7±5.6 ms(P<0.01),17.8±8.4 ms versus 11.3±6.1 ms(P<0.01);the relative amount of NCX protein did not differ from those of control group(P>0.05).Conclusion:The study did not find NCX protein upregulation,which might play no role in the electrical remodeling due to short-term pacing in doxobubicin-induced cardiomyopathy.