Yamashita T, Nakajima T, Hazama H, Hamada E, Murakawa Y, Sawada K, Omata M
Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Circulation. 1995 Nov 15;92(10):3061-9. doi: 10.1161/01.cir.92.10.3061.
Recent experimental and clinical studies on atrial flutter have demonstrated that the crista terminalis (CT) plays an important role in the genesis of atrial reentry. To elucidate the underlying mechanism of its role, we characterized the electrophysiological repolarization properties of CT cells by comparing them with those of the pectinate muscles (PM).
After action potential properties of both regions were compared by conventional microelectrode technique in multicellular atrial tissues, the whole-cell clamp experiments were applied in atrial cells isolated from both regions. Action potential duration (APD) was more prolonged in CT than in PM in multicellular preparations (APD90 77 +/- 5 ms versus 52 +/- 8 ms at 1 Hz, P < .01), though the other properties did not differ significantly. Similarly, in isolated atrial cells, APD was more prolonged in CT cells than in PM cells (APD90 63 +/- 7 ms versus 41 +/- 6 ms at 0.1 Hz, P < .01). Isolated single cells were larger in CT than in PM. The whole-cell clamp recordings showed no definite distinctions in the density of the voltage-dependent L-type Ca2+ current and the inwardly rectifying K+ current between these cells but revealed a significant reduction of the density of the 4-aminopyridine-sensitive transient outward current (Ito) in CT cells compared with that in PM cells (6.3 +/- 0.7 pA/pF versus 10.3 +/- 0.8 pA/pF at +20 mV, P < .05). However, no differences in the kinetics or the voltage dependence of Ito were observed between the cells. The time course of recovery from inactivation of Ito was also similar in both types of cells.
These results suggest that the preferential reduction in the density of Ito in the CT cells could contribute to prolong their APD, which may be related to the genesis of atrial reentry.
近期关于心房扑动的实验和临床研究表明，界嵴（CT）在心房折返的发生中起重要作用。为阐明其作用的潜在机制，我们通过将CT细胞与梳状肌（PM）细胞的电生理复极特性进行比较，对CT细胞进行了特性分析。
采用传统微电极技术在多细胞心房组织中比较了两个区域的动作电位特性后，对从两个区域分离的心房细胞进行了全细胞膜片钳实验。在多细胞标本中，CT的动作电位时程（APD）比PM延长（1 Hz时APD90为77±5 ms对52±8 ms，P<.01），尽管其他特性无显著差异。同样，在分离的心房细胞中，CT细胞的APD比PM细胞延长（0.1 Hz时APD90为63±7 ms对41±6 ms，P<.01）。分离的单个细胞CT比PM大。全细胞膜片钳记录显示这些细胞之间电压依赖性L型钙电流和内向整流钾电流密度无明确差异，但与PM细胞相比，CT细胞中4-氨基吡啶敏感的瞬时外向电流（Ito）密度显著降低（+20 mV时为6.3±0.7 pA/pF对10.3±0.8 pA/pF，P<.05）。然而，细胞之间未观察到Ito的动力学或电压依赖性差异。两种类型细胞中Ito从失活恢复的时间进程也相似。
这些结果表明，CT细胞中Ito密度的优先降低可能有助于延长其APD，这可能与心房折返的发生有关。
