缺血预适应对心肌微循环内皮功能的保护作用

目的 探讨缺血预适应对心肌微循环内皮功能的作用。方法 复制套扎前降支冠状动脉犬模型。缺血预适应组先给予缺血5min，灌注5min，反复4次，然后缺血1h，再灌注2h；缺血再灌注组给予缺血1h后再灌注2h；两组分别于基础、缺血1h、再灌注2h采集冠状窦血对比分析一氧化氮和内皮素水平，并于再灌注2h对比分析注射乙酰胆碱前后心肌声学造影强度变化，最后用Evan氏兰和TIC双染。结果（1）正常心肌注药后声学强度增强，而缺血心肌反而下降，与再灌注组相比，预适应组缺血区心肌声学强度下降程度显著减轻（P〈0．01）；（2）两组缺血后一氧化氮水平均显著下降（P〈0．01），再灌注2h下降更为明显（P〈0．05），然而预适应组缺血1h与再灌注2h下降程度均小于再灌注组（P〈0．05）；（3）预适应组于缺血1h、再灌注2h内皮素水平比基础有所下降，再灌注组与基础比反而呈升高趋势，但未达统计学水准（P〉0．05），两组相比，预适应使缺血1h和再灌注2h的ET水平显著下降（P〈0．05）。结论 缺血预适应对心肌微循环内皮依赖性舒血管反应及一氧化氮和内皮素水平的调节具有保护效应。

Protection of Ischemic Preconditioning on the Endothelial Function in Myocardial Microcirculation

Objective To explore the effects of ischemic preconditioning on the endothelial function.Methods Anesthetized open-chest dogs in ischemic preconditioning(IP)group(n=6)were subjected to 5min occlusion and 5min reperfusion for 4 times,then 1 hour occlusion and 2 hours reperfusion in left descending coronary artery(LDA),while ischemia-reperfusion(IR)group(n=6)was observed for 40min without any stimulation and then subjected to 1 hour occlusion as well as 2 hours reperfusion.Blood specimens were collected from coronary sinus at interval of base,1 hour occlusion,2 hours reperfusion to measure the concentrations of NO and endothelin.Myocardium was stained by Evans blue and TTC finally.Statistical comparative analysis was made.Results(1) Acoustics intensity increased after injection of acetylcholine in normal myocardium.On the contrary,it decreased in the ischemic myocardium.With comparison to IR group,in IP group the severity of acoustics intensity decreased in ischemic myocardium significantly(P<0.01).(2)Nitrogen oxide concentration notably descended in both groups(P<0.01),and it descended more at the time of 2 hour reperfusion(P<0.05).However,the extent of descending was smaller in IP group than in control group at the 1 hour ischemia and 2 hour reperfusion(P<0.05).(3)Endothelin went down in IP group while went up in IR group vs their base,but both were not significant(P>0.05).Comparing tow groups,endothelin level decreased apparently in IP group at 1 hour ischemia and 2 hour reperfusion(P<0.05).Conclusion Ischemic preconditioning may have protective effects on the endothelium-dependent vascular reaction in the myocardial microcirculation and on beneficial adjustment of releasing nitrogen oxide and endothelin.