Sada H, Ban T, Sperelakis N
Department of Pharmacology, School of Medicine, Yamaguchi University, Ube, Japan.
Jpn J Pharmacol. 1996 Apr;70(4):303-12. doi: 10.1254/jjp.70.303.
To examine taurine actions on the rate of repolarization of action potentials (AP), L-type Ca2+ (ICa), late outward K+ (Ik) and the inward rectifier currents as affected by the external Ca2+ concentrations ([Ca2+]o), whole-cell voltage-clamp and current-clamp experiments were conducted in guinea pig ventricular myocytes. At a high (3.6 mM) [Ca2+]o, 10 mM taurine suppressed both ICa and IK, shortened AP duration and decelerated the rate (-dV/dt) of terminal repolarization of AP. In contrast, at a low (0.9 mM) [Ca2+]o, taurine intensified both ICa and IK, lengthened AP duration and accelerated -dV/dt. However, at either [Ca2+]o, the resting membrane potential was slightly hyperpolarized, and the inward rectifier, current examined by the ramp-pulse protocol remained unaffected by taurine. Taurine is suggested to maintain a stable AP duration by altering the inward Ca2+ and IK in the opposite directions, depending on [Ca2+]o. The relevance of the stabilizing action of taurine on the AP duration to its reported anti-arrhythmic efficacies is discussed.
为研究牛磺酸对动作电位（AP）复极化速率、L型Ca2+（ICa）、延迟外向K+（Ik）以及受细胞外Ca2+浓度（[Ca2+]o）影响的内向整流电流的作用，在豚鼠心室肌细胞中进行了全细胞电压钳和电流钳实验。在高（3.6 mM）[Ca2+]o时，10 mM牛磺酸抑制ICa和IK，缩短AP持续时间并减慢AP终末复极化速率（-dV/dt）。相反，在低（0.9 mM）[Ca2+]o时，牛磺酸增强ICa和IK，延长AP持续时间并加快 -dV/dt。然而，在任一[Ca2+]o时，静息膜电位均轻度超极化，且通过斜坡脉冲方案检测的内向整流电流不受牛磺酸影响。提示牛磺酸可根据[Ca2+]o通过相反方向改变内向Ca2+和IK来维持稳定的AP持续时间。讨论了牛磺酸对AP持续时间的稳定作用与其报道的抗心律失常疗效的相关性。
