心肌缺血时心室肌细胞的动作电位交替与镁的抗电交替作用

Alternans of ventricular action potential during myocardial ischemia and the anti-alternating effect of magnesium

在模拟缺血条件下，采用程序电刺激的方法，观察离休豚鼠心室肌细胞动作电位交替（ＡＡＰ）的发生、演变和消失过程及镁对ＡＡＰ的影响。结果表明：缺血初期首先出现２：１的动作电位时程交替，然后出现２：１的动作电位振幅交替，随着缺血时间延长，低窄的动作电位逐渐减小，最后消失，ＡＡＰ一般历时约３０ｍｉｎ。随着刺激频率的增快，ＡＡＰ出现率明显增多，交替程度增大。镁对“缺血”性ＡＡＰ有明显拮抗作用。

The evolution of alternans of ventricular action potentials(AAP)byprogrammed stimulation were observed in isolated guinea pig papillary muscles exposed tomimic ischemic Tyrode′s solution(glucose free,high K￣(+),low pH and 100%N_2).In mimicischemic ventricular muscles, the occurrence of duration preceded that of amplitude of the2:1 alternans of action potential.With increasing ischemic intervals,the lower alternatingaction potentials reduced progressively and vanished eventually. The AAP usually lasted for30 min or so. The incidence of alternans and the degree of alternation increased significantlyas basic cycle length(BCL)of stimulation shortened. Magnesium showed a marked antago-nistic effect on AAP during myocardial ischemia.