Wang Teng, Huang Cong-xin, Jiang Hong, Tang Qi-zhu, Yang Bo, Li Geng-shan
Department of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute of Wuhan University, Wuhan 430060, China.
Zhonghua Yi Xue Za Zhi. 2009 Dec 1;89(44):3138-42.
To investigate the properties of electrophysiology and effects of ouabain upon transient outward potassium current (I(to)) and L-type calcium current (I(Ca-L)) of left atrium posterior wall (LAPW) and left atrium appendage tissue (LAA)in rabbit so as to provide the scientific explanations that LAPW and ouabain can enhance atrial fibrillation (AF) vulnerability through increasing electrophysiological heterogeneity and electrical remodeling of different regions of left atrium in rabbits.
Atrial myocytes from LAPWs and LAAs of rabbits on an in vitro heart perfusion system were obtained by enzymatic dissociation. The whole-cell patch-clamp technique was used to assess the effects of ouabain upon I(to) and I(Ca-L). The current-voltage (I-V) curves of I(to) and I(Ca-L) in LAPW and LAA myocytes were fitted before and after ouabain administration.
(1) With holding potential +50 mV and commanding potential +50 mV, the current densities of LAPW I(to) decreased slightly less than that of LAA I(to) in control groups (P > 0.05). After ouabain administration, the current densities of LAPW I(to) were significantly larger than that of LAA I(to) [(10.97 +/- 0.58) pA/pF vs (9.39 +/- 0.83) pA/pF, P < 0.05]. The I-V curve of LAPW I(to) was slightly lowered to I-V curve of LAA I(to) in control groups. But with perfusion of ouabain, the I-V curve of LAPW I(to) opposed to I-V curve of LAA I(to) significantly changed from the bottom to the top with the same upward direction. (2) With the voltage clamp protocol of I(Ca-L), the current densities of LAPW I(Ca-L) markedly decreased compared with that of LAA I(Ca-L) in control groups (P < 0.05). With the addition of ouabain, the peak of amplitude of LAPW I(Ca-L) at +20 mV obviously increased to that of LAA I(Ca-L) [(-11.13 +/- 0.99) pA/pF vs (-8.86 +/- 0.51) pA/pF, P < 0.01]. In the control groups, the I-V curve of LAPW I(Ca-L) was shifted to the bottom of all I-V curves of I(Ca-L). Through the effects of ouabain, the I-V curve of LAPW I(Ca-L) was completely upgraded to the top of other I-V curves of I(Ca-L). However, all shapes and directions of current peak of I-V curves of I(Ca-L) remained unchanged in both groups.
The distribution properties of I(Ca-L) have significant difference in LAPW. Ouabain can accentuate the electrophysiological heterogeneity and electrical remodeling of I(to) and I(Ca-L) in LAPW of rabbits. It may become the triggering factor and persisting basis of AF vulnerability.
研究哇巴因对兔左心房后壁（LAPW）和左心耳组织（LAA）的电生理特性以及瞬时外向钾电流（I(to)）和L型钙电流（I(Ca-L)）的影响，为LAPW和哇巴因通过增加兔左心房不同区域的电生理异质性和电重构来增强房颤（AF）易感性提供科学解释。
采用酶解法从体外心脏灌注系统中获取兔LAPW和LAA的心房肌细胞。运用全细胞膜片钳技术评估哇巴因对I(to)和I(Ca-L)的影响。在给予哇巴因前后，对LAPW和LAA肌细胞中I(to)和I(Ca-L)的电流-电压（I-V）曲线进行拟合。
（1）在钳制电位为+50 mV且指令电位为+50 mV时，对照组中LAPW的I(to)电流密度下降幅度略小于LAA的I(to)电流密度（P>0.05）。给予哇巴因后，LAPW的I(to)电流密度显著大于LAA的I(to)电流密度[（10.97±0.58）pA/pF对（9.39±0.83）pA/pF，P<0.05]。对照组中LAPW的I(to)的I-V曲线略低于LAA的I(to)的I-V曲线。但在灌注哇巴因后，LAPW的I(to)的I-V曲线与LAA的I(to)的I-V曲线明显从底部向顶部且向上方向相同地发生了变化。（2）采用I(Ca-L)的电压钳制方案时，对照组中LAPW的I(Ca-L)电流密度与LAA的I(Ca-L)电流密度相比明显降低（P<0.05）。加入哇巴因后，+20 mV时LAPW的I(Ca-L)的电流峰值明显增加至LAA的I(Ca-L)的电流峰值[（-11.13±0.99）pA/pF对（-8.86±0.51）pA/pF，P<0.01]。对照组中，LAPW的I(Ca-L)的I-V曲线移至所有I(Ca-L)的I-V曲线的底部。通过哇巴因的作用，LAPW的I(Ca-L)的I-V曲线完全升至其他I(Ca-L)的I-V曲线的顶部。然而，两组中I(Ca-L)的I-V曲线的电流峰值的所有形状和方向均保持不变。
LAPW中I(Ca-L)的分布特性存在显著差异。哇巴因可加剧兔LAPW中I(to)和I(Ca-L)的电生理异质性和电重构。它可能成为AF易感性的触发因素和持续基础。
