短期力竭运动对大鼠心肌细胞电生理特性的影响

Short-Term Exhaustive Exercise Regulates Cell Electrophysiological Properties in Rat Ventricular Myocytes

目的观察短期力竭运动对大鼠心电图、心脏结构、心脏功能及心肌细胞钠离子通道的影响,探讨力竭运动时心律失常发生的机制。方法所有SD大鼠进行为期3d的游泳训练,随后开始9d的负重游泳运动,负重为体重的5%。在第1~9天,每天上午9点开始进行次游泳运动。力竭运动判断标准为大鼠水中旋转、运动协调性显著下降,水淹没鼻尖,身体下沉至再次浮出水面超过10秒。9天力竭运动后,利用全细胞膜片钳技术记录心肌细胞钠离子通道变化,电生理仪检查心电图改变,通过超声心动图检测心脏结构和功能变化。结果与大鼠运动前相比,运动后大鼠心脏左室射血分数和短轴缩短率下降,但差异无统计学意义。运动前后左室后壁厚度、室间隔厚度、左室内径、舒张末期容积和左心室心肌质量改变无统计学差异。心电图结果显示,与运动前相比,运动后P波振幅、时限、QRS波和R波振幅明显增加,而运动前后心率、PR间期、QRS时限、QT间期、R波振幅、S波振幅、T波振幅改变无统计学差异。心肌全细胞膜片钳检测发现,与运动前相比,运动后钠离子电流密度明显增大,但力竭运动并没有改变钠离子的稳态激活和失活曲线。结论短期力竭运动对心脏的结构和功能无明显影响,但是增加了P波振幅、时限、QRS波和R波振幅,提示心肌细胞去极化受损,而运动后钠离子电流密度改变可能是引起心肌细胞去极化受损的基础。

Objective To investigate the effect of exhaustive exercise on sodium channel currents(INa),ECG and echocardiography parameters in a rat swimming model.Methods Rats of the exercise group were forced to swim until exhaustion each time for 9 days with 5%body weight(workload)attached to the head.A swimming session will be held at 9 am from day 1 to day 9.The criteria of exhausting exercise included the rotatingmotion in water,the significant decrease in motor coordination,and more than 10 seconds from water submerged the nose to the body resurfaced.After 1 day of recovery period,we performed ventricular myocytes isolation and used whole cell patch-clamp technique to investigate sodium channel currents,sedentary rats served as controls.In addition,echocardiography and ECG parameters were analyzed.Results After 9 days of swimming exercise,a decrease in EF and FS%was observed,however,no significant differences were found between sedentary and exercise group.In addition,no significant differences were found in heart rate,LVPWs,LVPWd,IVSs,IVSd,LVIDs,LVIDd,EDV,LV Mass between sedentary and exercise group.The following ECGs parameters were increased:P wave amplitude,P wave duration,QRS amplitude and R wave amplitude,while the other parameters remained unchanged.When compared to sedentary,peak INa density was enhanced by exhaustive exercise,however,exhaustive exercise didn’t change the steady-state activation and inactivation of INa.Conclusion The P,QRS and R-wave amplitudes increased after exhaustive exercise indicating impaired myocardial depolarization,which may be caused by the enhanced INa.These changes could shorten the action potential,and thus may contribute to proarrhythmia in cardiomyocytes.