低渗性肿胀对豚鼠心室肌细胞动作电位及延迟整流钾电流的影响

观察单个豚鼠心室肌细胞动作电位和主要复极期电流延迟整流钾电流(IK)的变化,探讨急性心肌缺血再灌注室性心律失常发生的离子机制。采用全细胞膜片钳记录技术,观察低渗液(200mOsm/kg)灌流胶原酶分离的单个豚鼠心室肌细胞发生肿胀后的动作电位各参数的变化,同时记录IK及其快、慢两种激活成分(IKr及IKs)的变化。结果:低渗液灌流后心室肌细胞迅速发生肿胀,动作电位幅度(APA)、静息膜电位(RMP)及阈电位水平无明显变化;而动作电位时程(APD)在600,1000和3000ms三种基础起搏周长(BCL)刺激时均缩短(P<0.05),尤以APD复极达50%和90%时缩短更为明显。APD生理性频率适应性消失且离散度增大。低渗性肿胀状态下IK电流幅度在3000ms长去极化保持时间(主要成分为IKs)刺激时从1134.33±150.17pA增加至1621.98±234.95pA(P<0.001,n=10);而在100ms短去极化保持时间(主要成分为IKr)刺激时从693.44±96.44pA降低至294.06±71.79pA(P<0.05,n=8);并且使IK的IV曲线向上移位。结论:低渗性肿胀的心室肌细胞IK特别是IKs的增加是引起APD缩短的重要因素,是急性心肌缺血再灌注室性心律失常发生的离子机制之一。

The Effect of Hyposmotic Swelling on Action Potential and Delayed Rectifier Potassium Current in Guinea Pig Ventricular Myocytes

The effects on action potential (AP) and delayed rectifier potassium current (I_K) in single guinea pig ventricular myocyte exposure to hyposmotic solution and the mechanism of ventricular arrhythmia of myocytes under hyposmotic swelling conditions were studied. Whole cell patch clamp technique was used to investigate the changes of AP, I_K and its two subtypes (I_ Kr and I_ Ks) of single guinea pig ventricular myocyte isolated by collagenase. Results: The hyposmotic swelling of myocytes had no effect on AP amplitude (APA), resting membrane potential(RMP) and threshold potential, but APD (action potential duration) shortened at the BCL (basic cycle length) of 600,1 000 and 3 000 ms. Especially, repolarization to 50% (APD_ 50) and 90% (APD_ 90) were significantly shortened under hyposmotic swelling conditions. Furthermore, physiological frequency dependency of APD disappeared and the degree of dispersion increased. The amplitude of I_K in which I_ Ks was its principal component increased from 1134.33±150.17 pA to 1621.98±234.95 pA(P<0.001,n=10) for longer depolarization time; and decreased from 693.44±96.44 pA to 294.06±71.79 pA (P<0.05,n=8) for shorter depolarization time. And caused the I-V curve of I_K upwards. Conclusion: The increase of I_K, especially I_ Ks, in the ventricular myocytes is the main mechanism of the APD shorting, and can be considered as one of the ion mechanism of acute myocardial ischemia-reperfusion arrhythmia.