妥卡尼对豚鼠心室肌细胞钙电流和钾电流的抑制作用

利用酶分散的成年豚鼠心室肌细胞和全细胞电压钳技术,研究了妥卡尼(tocainide)对心室肌细胞钙电流(I_ca)、延迟整流钾电流(I_k)和ATP敏感性钾电流(Ik,ATP)的作用。结果表明,妥卡尼对I_ca和I_k均显示浓度相关的抑制作用,妥卡尼50umol·L^-1对I_ca和I_k的抑制率分别为16%和3%。这可能是妥卡尼有效抑制室上性心动过速和缩短心肌动作电位平台期的重要机制。

INHIBITORY EFFECT OF TOCAINIDE ON CALCIUM CURRENT AND POTASSIUM CURRENT IN GUINEA PIG VENTRICULAR MYOCYTES

In whole cell voltage clamp experiment with isolated guinea pig ventricularmyocytes,tocainide was shown to exhibit a concentration-dependent inhibition of calcium current(I_ca)and deldyed rectifiet potassium current(I_k).Tocainide with a therapeutic concentration of 50umol·L^-1 significantly inhibited the I_ca and Itail(deactivating tail current of Ik)by 16%and 3%respectively.Inhibition of I_ca by tocainide was also shown to be dependent upon stimulatingfrequencies,with a greater blockade occurring at 2.0 Hz (57%)than at 0.2 Hz(17%).Tocainidewas found to inhibit the I_k,ATP by 74%at 200 umol·L^-1 but not at 50 umol·L^-1.These inhibitoryeffects on Ica and I_k can probably explain the therapeutic effect of tocainide on supraventriculartachycardia,and the shortening of plateau phase of action potential.