高胆固醇血症家兔心脏单相动作电位及钙电流的特征

Characteristics of Monophasic Action Potential and Calcium Current of Heart in Rabbit with Hyperlipidemia

目的观察高胆固醇血症对家兔心脏单相动作电位及钙电流的影响。方法24只家兔分为高胆固醇饮食组和对照组各12只,分别给予高胆固醇饲料和标准饲料饲养10周后,检测血脂、心电图和室颤阈值,记录离体灌流心脏单相动作电位,并记录心室肌细胞的L型钙通道电流。结果高胆固醇饮食组兔的血脂水平明显高于对照组(P<0.01);室颤阈值(10.2±1.7)V,低于对照组的(13.9±1.3)V(P<0.05);单相动作电位复极90%的时程(MAPD90)较对照组延长并呈更明显的逆频率依赖性,在1500ms起搏时MAPD90为(348±21)ms,而对照组为(271±16)ms;心室肌细胞的L型钙通道电流密度为(14.7±0.8)pA/pF,明显高于对照组的(10.9±1.1)pA/pF(P<0.01)。结论高胆固醇血症家兔的心脏单相动作电位及心肌细胞L型钙通道电流明显改变,复极时程延长,室颤阈值降低。

Objective To investigate the effect of hyperlipidemia on monophasic action potential and calcium current of heart in rabbits. Methods 24 rabbits were divided into the high cholesterol group （n= 12） and control group （n= 12） and fed with high cholesterol forage and standard forage respectively for 10 weeks. Electrocardiograph, ventricular fibrillation threshold and the level of serum lipid were examined. Whole-cell patch clamp technique was used to record LCa-L. Results In high cholesterol group, the serum cholesterol level was higher than the control group （ P 〈0.01）, ventricular fibrillation threshold （10.2±1.7 V） lower than that of the control group （13.9 ± 1.3 V）（ P 〈0.05）, MAPD90 displayed more significant rate-dependent prolongation. At cycle lengths of 1500 ms, MAPD30, was 358±18 ms in the high cholesterol group, while it was 277±20 ms in the control group. The densities of ICa L were larger in the high cholesterol group （14.7±0.8 pA/pF） than that in the control group （10.9±1.1 pA/pF）（P 〈0.01）. Conclusion Hypercholesterolemia can produce cardiac electrical remodeling, including increased ICa L, prolonged repolarization and decreased ventricular fibrillation thresholds.