低温、钾通道开放剂停搏对幼兔心肌的保护作用

Experimental study of the immature myocardial protection of potassium channel openers in hypothermia and cardioplegia

目的探讨以钾通道开放剂(PCOs)取代传统的高钾用作停搏剂时对未成熟心肌的保护效果,以及低温与PCOs之间的关系。方法32颗未成年(14-28 d兔龄)兔心进行Langendoff模型缺血/再灌注研究:对照组(C组,n=8),改良St.Thomas液灌注心脏停跳,15℃保存;实验Ⅰ组(T1组,n=8),单纯低温心脏自然停跳,15℃保存;实验Ⅱ组(T2组,n=8),4℃Pinacidil(50μmol/L)液灌注停跳,15℃保存;实验Ⅲ组(T3组,n=8),37℃Pinacidil(50μmol/L)液灌注停跳,37℃常温保存。观察缺血前后心功能(左心室收缩峰压、舒张末压、最大压力变化速率)、冠状动脉流量、生化指标、心肌含水量、心肌超微结构等的改变。结果T2组左室功能和冠脉流量的恢复均优于另外3组(P<0.01),而在左室收缩功能的恢复方面,T1组优于C组(P<0.05),T1组与T3组间无明显差异(P>0.05);再灌注后心肌酶外漏及超微结构改变以T2组最为轻微,T3组最重;心肌含水量各组间无显著性差异(P>0.05)。结论PCOs超极化停搏液对未成熟心肌的保护效果明显优于高钾停搏液;单纯低温即能对未成熟心肌提供良好的保护作用;低温与超极化停搏之间的作用互相增强,但高钾去极化停搏削弱低温对未成熟心肌的保护作用。

Objective To evaluate the cardioplegic protective effect of potassium channel openers （PCOs） as an alternative to replace hyperkalemic solution on immature rabbit myocardium and the relationship between PCOs and hypothermia. Methods A total of 32 immature （14- 28 days old） rabbit hearts were used to study the ischemic and reperfusion on model Langendoff. Control group （group C, n = 8）.. cardioplegia by reperfusion with modified St. Thomas solution, stored at 15℃ ; Test group [ （group T1, n = 8） ： cardioplcgia by hypothermia, stored at 15 ℃ ; Test groupⅡ （group T2, n =8）： cardioplegia by 4 ℃ Pinacidil solution （50μmol/L）, stored at 15 ℃ ; Test group m （group T3, n =8） ： cardioplegia by 37 ℃ Pinacidil solution （50 μmol/L）, stored at 37 ℃. Recovery of left ventricle performance （LVDP, LVEDP, ± dp/dtmax）, coronary blood flow（CF）, enzymologic marker and water content and ultrastructure of the myocardium were measured after reperfusion. Results Group T2 provided significant better recovery of left ventricle performance and coronary blood flow than that in the other three groups; and as for the recovery of systolic function, group T1 was better than group C . On the assessment to enzymologic marker and ultrastructure, group T2 was the best and group T3 was the worst. Conclusion Cardioplegia by potassium channel openers is superior to St. Thomas＇ Hospital solution on immature rabbit myocardial protection, and the protective effect of simple hypothcrmia is excellent too, and they enhance each other. But the hyperkalemic arrest weakens the protective effect of hypothermia on the immature rabbit myocardium.