酸性液后处理对离体大鼠心肌缺血再灌注损伤保护作用的研究

Acidic buffer post-conditioning protects isolated rat hearts against ischemia-reperfusion injury:the role of mitochondrial permeability transition pore

目的通过心脏停搏液停搏的离体大鼠心脏模型,评价酸性缓冲液或者含有环孢素A(CsA)的酸性缓冲液是否具有心肌保护作用,其机制是否与抑制线粒体通透性转换孔开放有关。方法取SD大鼠心脏,建立离体Langendorff心肌缺血再灌注模型,随机分为3组(每组12只)。对照组(Con组):经历平衡期20 min,St.ThomasⅡ停搏液灌注后常温缺血30min,KH缓冲液[pH:(7.4±0.5)]再灌注60 min。酸性后处理组(Low pH组):再灌注开始3 min给予酸性KH缓冲液灌注(pH:6.8)。酸性缓冲液联合环孢素A后处理组(Low pH+CsA组):再灌注开始3 min给予含有0.2μmol/L环孢素A的酸性KH缓冲液灌注(pH:6.8)。检测各组血流动力学指标,Western blot法检测胞浆细胞色素C含量和总蛋白Bcl-2/Bax含量,线粒体肿胀液检测线粒体对Ca2+的敏感度,TUNEL法检测心肌细胞凋亡。结果与Con组相比,Low pH组和Low pH+CsA组在再灌注期间,左室发展压,等容收缩期左心室内压力上升的最大速率,等容舒张期左心室压力下降的最大速率以及心率明显优于Con组(P<0.05)。Low pH组和Low pH+CsA组的胞浆细胞色素C释放较Con组明显减少(P<0.05),同时Bcl-2/Bax明显高于Con组;再灌注5 min线粒体肿胀率测定,两组线粒体对Ca2+诱导的通透性转换孔开放敏感度较Con组明显降低(P<0.05)、且心肌细胞凋亡数明显低于Con组(P<0.05)。结论酸性液后处理或联合环孢素A后处理能够减轻再灌注损伤引起的线粒体通透性增加,减少心肌细胞凋亡,改善心脏血流动力学功能。但添加环孢素A并不能增强其保护作用。酸性液后处理有可能作为一种新的心肌保护方法应用于心脏手术。

OBJECTIVE To analyze the protective value of acidic buffer with/without cyclosporine A（a potent inhibitor of mitochondrial permeability transition） in isolated rat hearts after cardioplegic arrest.METHODS Langendorff-perfused Sprague-Dawley rat hearts were perfused for 20 minutes with Krebs-Henseleit buffer followed by 30 minutes of normothermic crystalloid cardioplegia and 60 minutes of reperfusion.In the control group（Con group,n=12）,hearts were reperfused with Krebs-Henseleit buffer.In the acidic buffer post-conditioning group（Low pH group,n=12）,hearts were reperfused with acidic KH buffer（pH 6.8） for the first 3 min of reperfusion.In the acidic buffer plus cyclosporine A group（Low pH＋CsA group,n=12）,hearts were perfused with KH acidic buffer（pH 6.8） containing cyclosporine A（0.2 μmol/L） for the first 3 min of reperfusion.RESULTS Compared with that in the Con group,the myocardial performance significantly improved,cytochrome C released into the cytosol significantly decreased,Bcl-2 immunoreactivity significantly increased,Bax immunoreactivity significantly decreased,sensitivity of mPTP-opening to Ca2＋ significantly decreased and the rate of apoptoic myocytes significantly decreased in the Low pH group and Low pH＋CsA group.CONCLUSION These findings suggest that acidic buffer or plus cyclosporine A post-conditioning can prevent apoptosis-related mitochondrial permeabilization after cardioplegic arrest.This protection is correlation with improved myocardial performance.But addition of cyclosporine A post-conditioning does not show much better than acidic buffer alone.Prevention of mitochondrial permeability transition pore opening by acidic buffer at reperfusion may be a novel target for myocardial preservation after cardioplegic arrest.