Wu B W, Sheng B T, Wang W Z, Zhao R R
Department of Physiology, Shanxi Medical College, Taiyuan.
Yao Xue Xue Bao. 1995;30(6):412-6.
In whole cell voltage clamp experiment with isolated guinea pig ventricular myocytes, tocainide was shown to exhibit a concentration-dependent inhibition of calcium current (ICa) and delayed rectifier potassium current (IK). Tocainide with a therapeutic concentration of 50 mumol.L-1 significantly inhibited the ICa and Itail (deactivating tail current of IK) by 16% and 3% respectively. Inhibition of ICa by tocainide was also shown to be dependent upon stimulating frequencies, with a greater blockade occurring at 2.0 Hz (57%) than at 0.2 Hz (17%). Tocainide was found to inhibit the IK,ATP by 74% at 200 mumol.L-1 but not at 50 mumol.L-1. These inhibitory effects on ICa and IK can probably explain the therapeutic effect of tocainide on supraventricular tachycardia, and the shortening of plateau phase of action potential.
在对分离的豚鼠心室肌细胞进行的全细胞电压钳实验中，发现妥卡尼可呈现浓度依赖性地抑制钙电流（ICa）和延迟整流钾电流（IK）。治疗浓度为50μmol·L-1的妥卡尼分别使ICa和IK的尾电流（IK的失活尾电流）显著抑制16%和3%。还显示妥卡尼对ICa的抑制也取决于刺激频率，在2.0Hz时的阻断作用（57%）大于0.2Hz时（17%）。发现妥卡尼在200μmol·L-1时可抑制IK,ATP达74%，但在50μmol·L-1时则无此作用。这些对ICa和IK的抑制作用可能解释了妥卡尼对室上性心动过速的治疗作用以及动作电位平台期的缩短。
