Effects of thymol on calcium and potassium currents in canine and human ventricular cardiomyocytes
作者:János Magyar、Norbert Szentandrássy、Tamás Bányász、László Fülöp、András Varró、Péter P Nánási
DOI:10.1038/sj.bjp.0704718
日期:2002.5
Concentration‐dependent effects of thymol (1–1000 μM) was studied on action potential configuration and ionic currents in isolated canine ventricular cardiomyocytes using conventional microelectrode and patch clamp techniques.
Low concentration of thymol (10 μM) removed the notch of the action potential, whereas high concentrations (100 μM or higher) caused an additional shortening of action potential duration accompanied by progressive depression of plateau and reduction of Vmax.
In the canine cells L‐type Ca current (ICa) was decreased by thymol in a concentration‐dependent manner (EC50: 158±7 μM, Hill coeff.: 2.96±0.43). In addition, thymol (50–250 μM) accelerated the inactivation of ICa, increased the time constant of recovery from inactivation, shifted the steady‐state inactivation curve of ICa leftwards, but voltage dependence of activation remained unaltered. Qualitatively similar results were obtained with thymol in ventricular myocytes isolated from healthy human hearts.
Thymol displayed concentration‐dependent suppressive effects on potassium currents: the transient outward current, Ito (EC50: 60.6±11.4 μM, Hill coeff.: 1.03±0.11), the rapid component of the delayed rectifier, IKr (EC50: 63.4±6.1 μM, Hill coeff.: 1.29±0.15), and the slow component of the delayed rectifier, IKs (EC50: 202±11 μM, Hill coeff.: 0.72±0.14), however, K channel kinetics were not much altered by thymol. These effects on Ca and K currents developed rapidly (within 0.5 min) and were readily reversible.
In conclusion, thymol suppressed cardiac ionic channels in a concentration‐dependent manner, however, both drug‐sensitivities as well as the mechanism of action seems to be different when blocking calcium and potassium channels.
British Journal of Pharmacology (2002) 136, 330–338; doi:10.1038/sj.bjp.0704718
研究结果表明,丁香酚可在浓度依赖性范围内改变犬孤立心室心肌细胞的动作电位形态,并影响离子电流。研究采用传统微电极和钳式电极技术,重点考察了1至1000 μM浓度范围内的丁香酚对动作电位配置和离子电流的影响。
在低浓度(10 μM)下,丁香酚可消除动作电位的切迹;而在高浓度(100 μM或更高)时,会导致动作电位时程的进一步缩短,同时伴随平台期逐渐减弱和V_max的减小。
针对犬心脏细胞中的L型钙电流(I_Ca),研究发现丁香酚会以浓度依赖性方式降低其电流幅度(EC50: 158±7 μM,Hill系数:2.96±0.43)。此外,50至250 μM浓度范围内的丁香酚会加速I_Ca的失活过程、增加其失活恢复的时间常数,并将稳态失活曲线左移,然而激活过程的电压依赖性保持不变。在健康人源心脏心肌细胞中,亦观察到与犬细胞相似的结果。
研究显示,丁香酚对钾电流具有浓度依赖性的抑制效应,具体表现为对外向瞬时电流I_to(EC50: 60.6±11.4 μM,Hill系数:1.03±0.11)、延迟整流快速组分I_Kr(EC50: 63.4±6.1 μM,Hill系数:1.29±0.15)和延迟整流慢组分I_Ks(EC50: 202±11 μM,Hill系数:0.72±0.14)的抑制作用。然而,丁香酚对K通道动力学的改变并不显著。有趣的是,这些作用(对钙电流和钾电流的抑制)迅速发生(0.5分钟内)且易于逆转。
综上所述,丁香酚以浓度依赖性方式抑制心脏离子通道。尽管钙通道和钾通道抑制的机制可能存在差异,表现出不同的药物敏感性,但均呈现出浓度依赖性抑制的特性。
该研究发表于《英国药理学杂志》(British Journal of Pharmacology)2002年136卷,330-338页,文章DOI为10.1038/sj.bjp.0704718。