哇巴因对大鼠心肌重构的作用

The effects of ouabain on myocardic remodeling in the rats

目的研究哇巴因对大鼠心肌重构的作用。方法雄性Sprague-Dawly(SD)大鼠22只随机分为哇巴因组(n=12)及对照组(n=10),经腹腔注射哇巴因[20μg/(kg·d)]和生理盐水[1mL/(kg·d)]8周构建动物模型。第6周,根据收缩压情况,将哇巴因组分为哇巴因敏感鼠(收缩压升高,n=10)和哇巴因抵抗鼠(收缩压没有明显升高,n=2)。电镜下观察3组心肌的超微结构变化,同时实时定量PCR检测其电压门控性K+通道4.2(Kv4.2)表达水平的变化;通过膜片钳方法研究哇巴因对大鼠心室肌细胞动作电位及瞬间外向钾电流(Ito)的影响。结果从第6周起,与对照组比较,10只哇巴因敏感鼠收缩压明显升高[(138.2±8.0)比(120.1±5.2)mmHg,P<0.01];2只哇巴因抵抗鼠收缩压无明显变化[(126.7±11.4)比(125.4±6.9)mmHg,P>0.05]。哇巴因敏感鼠电镜观察其左心室心尖部中层心肌组织可见线粒体肿胀等超微结构改变。哇巴因抵抗鼠心肌细胞超微结构较对照组差异无统计学意义。RT-PCR提示3组大鼠心肌Kv4.2表达差异无统计学意义。膜片钳结果提示哇巴因敏感鼠心室肌细胞动作电位时程延长,Ito密度下调,引起心肌电重构。结论哇巴因引起大鼠血压升高的同时引起心肌结构重构及电重构。

Objective To study the effects of ouabain on myocardic remodeling in the rats. Methods Twenty-two adult male Sprague-Dawly（SD）rats were randomly divided into two groups：ouabain group（n=12）which intraperitoneal injection with ouabain[20μg/（kg·d）],control group（n=10）which intraperitoneal injection with physiological saline[1mL/（kg·d）]for 8weeks. After 6weeks,rats in ouabain group were divided into＂ouabain-sensitive rats＂ [systolic blood pressureI（SBP）were increased,n=10]and＂ouabain-resistant rats＂ （no significant difference in SBP,n=2）. After 8weeks,the ultrastructural changes of myocardium were observed by electron microscope.The expression of mRNA of voltage-gated potassium channel 4.2（Kv4.2）were detected by real-time quantitative reverse transcripition-polymerase chain reaction（RT-PCR）. And the effects of ouabain on myocardia action potential and transient outward potassium current（Ito）were measured by patch clamp. Results After 6weeks continued infusion,the SBP of the ouabain-sensitive rats were markedly higher than those of the control group [（138.2±8.0）vs（120.1±5.2）mm Hg,P0.01]. The SBP of ouabain-resistant rats did not increase after 8 weeks treatment[（126.7±11.4）vs（125.4±6.9）mm Hg,P0.05]. There were some significant ultrastructure pathological changes including mitochondrial swelling in the mid-myocardium of apex in the ouabain-sensitive rats. Kv4.2expression had no difference among the ouabain-sensitive,ouabain-resistant rats and control rats. The clamp patch results showed that ouabain could prolong action potential duration（APD90）,decrease Ito,and trigger electrical remodeling of myocardium. Conclusion Ouabain can increase the blood pressure,trigger cardiac structural and electrical remodeling.