低pH液复灌对兔心肌缺血再灌注的保护作用与Bcl-2、Bax表达的关系

Correlation between protective effect of low pH solution reperfusion on myocardial ischemia/reperfusion and expression of Bcl-2 and Bax in rabbits

目的探讨低pH液复灌对体外循环(extracorporeal circulation,ECC)下兔缺血再灌注(ischemia/reperfusion,I/R)心肌的保护作用与Bcl-2、Bax表达的关系。方法成年新西兰大白兔30只,完全随机分为5组(n=6):对照组(C组)不停跳,体外循环180 min;缺血再灌注组(I/R组)全心缺血40 min,再灌注120 min;pH=7.4组与pH=6.9组于再灌注前2 min予37℃的95%O2+5%CO2饱和的pH值为7.4或6.9的K-H液灌注;缺血后处理组(P组)再灌注的前2 min给予缺血后处理。体外循环结束后,光镜观察心肌形态学变化;ELISA测定血清肌钙蛋白I(cardiac troponin I,cTnI)浓度;RT-PCR检测Bcl-2、Bax mRNA的表达;免疫组化检测Bcl-2、Bax蛋白的表达。结果与I/R组比较,pH=6.9组和P组心肌组织损伤较轻,cTnI浓度较低(P<0.05),pH=6.9组Bcl-2 mRNA和蛋白表达水平明显增高[(1.058 1±0.165 7)vs(0.648 2±0.070 8),(0.233 1±0.022 5)vs(0.156 5±0.019 2),P<0.05],Bax mRNA和蛋白表达水平明显降低[(1.353 3±0.138 1)vs(1.901 7±0.198 1),(0.173 5±0.015 1)vs(0.247 1±0.021 3),P<0.05];pH=6.9组和P组之间Bcl-2、Bax表达水平差异无统计学意义(P>0.05)。结论体外循环下再灌注初短暂低pH(pH=6.9)液复灌可以模拟缺血后处理的心肌保护作用,其保护机制与调节Bcl-2、Bax的表达有关。

Objective To study the correlation between protective effect of low pH solution reperfusion on myocardial ischemia/reperfusion（I/R） and expression of Bcl-2 and Bax in rabbits undergoing extracorporeal circulation.Methods Thirty adult New Zealand white rabbits were randomly divided into control group,I/R group,pH 7.4 group,pH 6.9 group,and post-ischemia conditioning group（6 in each group）.Rabbits in control group underwent extracorporeal circulation for 180 min,those in I/R group underwent reperfusion for 120 min after 40 min of myocardial ischemia,those in pH 7.4 group and pH 6.9 group received a K-H solution at 37 ℃ containing 95%O2＋5%CO2 at pH 7.4 or pH 6.9 in 2 min before they underwent reperfusion,and those in post-ischemia conditioning group were conditioned 2 min before they underwent reperfusion.Changes in their myocardial morphology were observed under light microscope,their serum cardiac troponin I（cTnI） level was measured by ELISA,expressions of Bcl-2 and Bax mRNA and protein were detected by RT-PCR and immunohistochemistry,respectively.Results The myocardial tissue injury was milder and the cTnI level was lower in pH6.9 group and post-ischemia conditioning group than in I/R group（0.648 2±0.070 8 vs 1.058 1±0.165 7,0.156 5±0.019 2 vs 0.233 1±0.022 5,P〈0.05）.The expression level of Bcl-2 mRNA and protein was significantly higher and the expression level of Bax mRNA and protein was significantly lower in pH 6.9 group than in I/R group and post-ischemia conditioning group（1.058 1±0.165 7 vs 0.648 2±0.070 8 and 0.233 1±0.022 5 vs 0.156 5±0.019 2,1.353 3±0.138 1 vs 1.901 7±0.198 1 and 0.173 5±0.015 1 vs 0.247 1±0.021 3,P〈0.05）.No significant difference was found in expression level of Bcl-2 and Bax mRNA and protein between pH6.9 group and post-ischemia conditioning group（P〈0.05）.Conclusion Transient low pH solution reperfusion can protect heart against I/R injury in rabbits undergoing extracorporeal circulation by mimicking the post-ischemic conditioning and regulating the expression of Bcl-2 and Bax.