Na^+/Ca2^(+)交换对狗心室肌细胞复极的影响  

Effect of Na^+/ Ca^(2+) Exchanger on the Repolarization of Canine Ventricle.

作　　者：巩燕[1] 王焱[1] Bela Szabo 

机构地区：[1]厦门大学医学院厦门中山医院心脏中心,福建厦门361004 [2]美国Okalahoma大学心律失常研究中心

出　　处：《中国心脏起搏与心电生理杂志》2005年第5期368-372,共5页Chinese Journal of Cardiac Pacing and Electrophysiology

摘　　要：探讨生理状态下Na+/Ca2+交换(NCX)双向模式的离子转换对复极的影响,以及在转换失调时是否为潜在的触发心律失常的机制。应用全细胞膜片钳技术研究单个心室肌细胞在不同频率刺激下动作电位时程(APD)的变化、药物干预改变NCX活性的条件下APD的变化以及与细胞舒张的关系。结果:固定频率(1.0Hz)刺激APD的变化范围和频率改变(0.6~1.0Hz)时APD的变化范围均在一个相对固定的膜电位(10~40mV)范围内。用10mmol/LEGTA缓冲细胞内游离钙后,APD的变异系数明显减小。而废除基质网功能及应用钙通道阻滞剂nifedip-ine并不改变APD的变异程度。因刺激频率减慢造成复极和细胞松弛的不匹配,从而导致后收缩的出现以及APD的延长。在强化NCX逆向活性的条件下穹隆膜电位显著降低,而APD显著延长。结论:在动作电位的复极过程中NCX的逆向模式和顺向模式应该与机械收缩和松弛有完美的匹配。生理状态下的心脏一旦这种匹配失调,NCX会向错误的方向运载钙,从而造成基质网内钙超载,诱发心律失常。To determine whether a mismatch between action potential （AP） repolarization and relaxation of the contraction has arrhythmogenic effect. We studied the AP and contraction of single myocytes from the left ventricle in adult mongrel dogs by patch-clamp system, which included beat-to-beat repolarization variability during different frequency stimulation as well as the relationship between AP and relaxation of the myocyte when enhancing the reverse mode of NCX. Results ： There was a variance in the repolarization between 10 mV and - 40 mV during the constant stimulation at 1.0 Hz or switching from 0.6 Hz to 1.0 Hz. After blocking the Ca2^＋ transient by intracellular dialysis with 10 mmol/L EGTA, the coefficient variability （ CV = SD/mean APD% ） significantly reduced. During a rate change of the stimulation from 0.6 Hz to 1.0 Hz, the AP duration increased, P 〈 0.05. Contraction was accompanied by an after-contraction （A-CON）. Substituting [ Na^＋ ] o with same amount of Li^ ＋ significantly decreased the dome of the AP, P 〈 0.05. Conclusions ： In keeping the normal function of canine myocyte, the reverse and forward activity of NCX should work in a well-matched manner with the rise and relaxation of the contraction. Otherwise it may be arrythmogenic even in a physiological heart. [ Chinese Journal of Cardiac Pacing and Electrophysiology, 2005,19 （5） ： 368 - 372 ]

关 键 词：电生理学 动作电位 复极 NA^+/CA^2+交换 早期/延迟后除级 后收缩 心室肌细胞 

分 类 号：R331.38[医药卫生—人体生理学]