高胸段硬膜外阻滞对大鼠心肌缺血再灌注损伤的保护作用

Protective effect of high thoracic segment epidural anesthesia on myocardium against ischemia-reperfusion injury in rats

目的:探讨高胸段硬膜外阻滞(HTEA)对大鼠心肌缺血再灌注损伤的保护作用及机制。方法:将40只Wister大鼠随机均分为4组。缺血再灌注组(I/R组,结扎左冠状动脉前降支造成缺血30 min后再灌注120 min);保护组(结扎前硬膜外腔注入0.5%罗哌卡因,0.125 ml/kg);对照组(仅在左冠状动脉前降支下穿线,但不结扎,在穿线15 min前硬膜外腔注入等量生理盐水);硬膜外阻滞组(左冠状动脉前降支下穿线但不结扎,在硬膜外注入0.5%罗哌卡因)。实验过程中监测心电,测定心率。实验结束后测定血清肌酸激酶-同工酶(CK-MB)、乳酸脱氢酶(LDH);用HE染色光学显微镜观察心肌结构,免疫组化法测定凋亡蛋白bax和bcl-2表达。结果:(1)I/R组3只大鼠因发生室颤而死亡,保护组仅1只发生室颤而死亡;(2)保护组大鼠硬膜外注入罗哌卡因后心率较用药前下降19%(P<0.05);(3)I/R组血浆CK-MB[(2564.750±372.889)U/ml∶(1022.250±161.760)U/ml]、LDH[(2719.125±382.131)U/L∶(584.875±124.470)U/L]较对照组明显升高(P均<0.01),保护组血浆CK-MB[(1779.750±215.997)U/ml]、LDH[(2131.750±491.442)U/L]比I/R组明显下降(P均<0.01);(4)光镜结果显示,I/R组大鼠心肌损伤严重,而保护组损伤明显减轻;(5)I/R组大鼠凋亡蛋白Bax表达明显高于对照组[(25.750±12.629)%∶(7.500±3.725)%,P<0.01],保护组Bax[(18.500±9.050)%]表达明显低于I/R组(P<0.01),而I/R组大鼠抗凋亡蛋白Bcl-2的表达明显低于对照组[(6.500±2.078)%∶(22.250±3.162)%,P<0.01],保护组Bcl-2[(17.250±1.328)%]的表达明显高于I/R组(P均<0.01)。I/R组Bax/Bcl-2比值明显高于对照组[(3.903±2.093)∶(0.397±0.285),P<0.01],而保护组Bax/Bcl-2比值(1.448±0.890)较I/R组明显降低(P<0.01)。结论:(1)大鼠心肌缺血30 min后再灌注120 min,能够造成心肌严重损伤;(2)低浓度罗哌卡因应用于高胸段硬膜外阻滞能够减轻缺血再灌注大鼠的心肌损伤;(3)心肌损伤的减轻可能与下调Bax蛋白表达,及上调Bcl-2蛋白表达有关。

Objective： To evaluate the protective effect of high thoracic segment epidural anesthesia （HTEA） on myocardium against ischemia-reperfusion injury in rats. Methods： Forty Wister rats were randomly averagely divided into four groups： Group of ischemia-reperfusion （I/R group）： ligation the ramus descendens anterior arteriae coronariae sinistrae of the rats for 30 minutes and then reperfusion for 120 minutes, protective group： received 0. 125%ropivacaine to epidural space 15 minutes before occlusion of coronary artery, while in control group., no ligated the coronary and normal saline was injected instead of 0. 125% ropivacaine, epidural block group： no ligated the coronary and received 0. 125% ropivacaine to epidural space. Blood samples were taken from femoral artery for determination of CK-MB and LDH level after experiment. The myocardium structure was observed by light microscope. The expression of apoptosis protein Bcl--2 and Bax proteins were detected by immunohisto-chemiscal method. Results： （i） There were three rats died because of ventricular fibrillation in group of I/R and only one in protective group; （2） The heart rate （HR）of rats in protective group decreased 19% than fundamental HR （P〈0.05） ; （3） The levels of CK-MB [（2564.750± 372. 889） U/mlvs. （1022. 250±161.760）U/roll andLDH[（2719.125±382.131） U/Lvs. （584.875±124.470） U/ L] in I/R group were higher than those of control group, but the levels of CK- MB, LDH in protective group obviously lower[（1779. 750±215. 997） U/roll ,[（2131. 750±491. 442） U/L] than those of I/R group （P〈0. 01） ; （4） The myocardium structure was injuried obviously in I/R group, but slightly in protective group; （5）The expression of Bax in I/ R group was higher than that of control group[-（25. 750±12. 629） %0 vs. （7. 500±3. 725） %, P〈0. 012,but the expression of Bax in protective group was lower[（18. 500±9. 050） %] than that of group of I/R（P〈0.01）. The expression of Bcl-2 in group of I/R was lower than that of control group [（6. 500±2. 078） % vs. （22. 250±3. 162） %, P〈 0. 012, but the expression of Bcl- 2 in protective group was higher [（17. 250± 1. 328） %] than that of group of I/R（P 〈0. 01）. The expression of Bax/Bcl-2 in I/R group was higher than that of control group[（3. 903 ±2. 093） vs. （ 0. 397±0. 285）, P〈0. 012 ,but it in protective group （1. 448±0. 890） was lower than that of I/R group （P〈0. 01）, Conclusion： （1） Myocardial I/R induced obvious injury in rats＇ myocardium; （2） HTEA with ropivacaine can protect myocardium against ischemia-reperfusion injury in rats; （3） The alleviation of myocardium injury may be related to lower expression of Bax and higher expression of Bcl-2 protein.