心麻痹液在缺血预处理产生心肌保护效应中的作用研究

THE FUNCTION OF CARDIOPLEGIA IN CARDIOPROTECTION PRODUCED BY ISCHEMIC PRECONDITIONING IN IMMATURE HEARTS

目的:利用Langendorff离体灌注模型研究缺血预处理(IPC)单独应用和与心麻痹液联合应用对兔未成熟心脏全心缺血再灌注的影响,以了解心麻痹液在IPC心肌保护效应中的作用。方法:新西兰幼兔,体重220g^280g,兔龄14d^21d。麻醉及肝素化后,快速开胸取出心脏,浸入4℃Krebs—Henseleit缓冲液,30s内主动脉插管行Langendorff灌注,用39℃经混合气(O2:CO2=9%:5%)平衡的Krebs—Henseleit缓冲液灌注。32只兔未成熟心脏随机分为四组:对照组Ⅰ(conⅠ,n=8),全心接受30min缺血、40min再灌注;IPC组(IPC,n=8),接受5min缺血、10min再灌注预处理(IPC)和30min缺血、40min再灌注;对照组Ⅱ(conⅡ,n=8),接受4℃的St.ThomasⅡ心麻痹液使心脏停跳和45min缺血、40min再灌注;IPC复合心麻痹液(IPC+St.Ⅱ,n=8),接受IPC、St.Ⅱ灌注和45min缺血、40min再灌注。记录心脏停跳前平稳灌注时冠脉流量(CF)、心率(HR)、左室发展压(LVDP)、左室压力最大上升和下降速度率(±dp/dtmax)作为基础值,并分别把再灌注后5、10、20、30、40min的CF、HR、LVDP、±dp/dtmax测定值表达为对其相应基础值的恢复率。记录IPC组与conⅠ在主动脉停灌后心脏缺血跳动时间,测定各组再灌注后冠脉流出液中肌酸激酶同工酶(CK-MB)及再灌注末心肌组织ATP含量。结果:复灌后IPC组与对照组Ⅰ相比在冠脉流出量(CF)、心率(HR)、左室发展压(LVDP)、左室最大上升和下降速度率(±dp/dtmax)恢复率无明显差别,肌酸激酶同工酶(CK-MB)漏出量有增多趋势(但P>0.05);IPC组在全心停灌后心脏缺血跳动时间明显延长(P<0.01),再灌注末心肌ATP含量显著减少(P<0.001)。而在IPC复合心麻痹液组HR、CF、LVDP及±dp/dtmax恢复率较对照组Ⅱ明显得以改善,且保存心肌ATP含量,肌酸激酶同工酶(CK-MB)漏出减少。结论:IPC在单独应用时不足以保护经历全心缺血再灌注损伤的兔未成熟心脏,反而有可能导致心肌细胞的损伤;而在与心脏停搏液合用时,IPC对经历全心缺血再灌注的兔未成熟心肌具有明显的保护作用。因此,在Langendorff离体灌注心脏模型,本研究首次观察到IPC心肌保护效应的获得需要心麻痹液的参与。

Objective：To I nvestigate the function of cardioplegia in IPC-induced cardioprotection through comparing the effects ischemic preconditioning（IPC） and IPC followed by cardioplegia on immature rabbhit hearts globally suffered ischemia-repefusion injury.Methods：New Zealand rabbits aged 14-21 days weighing 220-280g were used.The animals were ancethetized and heparinized.Chest was opened and heart was quickly removed and aorta was connected to Langendorff within 30s after excision.The hearts were prefused with Krebs-Henseleit buffer balanced with gas mixture（O2：CO2 = 9%：5%） at 60cm H2O（prefusion pressure）.IPC consisted of 5min global ischemia plus 10min reperfusion.Thirty two immature rabbit hearts were randomly divided into four groups： CONⅠ（n=8）,was only made globally ischemic by withholding perfusion for 30min followed by 40min reperfusion;IPCⅠ（n=8）,IPC and 30min noreperfusion followed by 40min reperfusion;CONⅡ（n=8）,a cardiac arrest was induced with 4℃St ThomasⅡ cardioplegia and 30min noreperfusion followed by 40min reperfusion.Coronary flow（CF）,HR,left ventricle developed pressure（LVDP）,and ±dp/dtmax were monitored at equilibration（baseline value） and the 5,10,20,30 and 40min after reperfusion.The values got after reperfusion were expressed as percentage of their baseline value.Myocardial enzyme in the coronary effluent,and myocardial energetic metabolism were also determined.Results：The four hemodynamics indexes have not significant difference between the IPC group and the CONⅠ.It took the IPC group much longer time to cardiac ischemia-beating（16.23±1.74min versus13.50±1.82min in controls P0.01）.The CK-MB leakage in IPC group was increased,although the results were not significantly different from the controlgnoup.The myocardial levels of ATP in preconditioning group at the end of the reperfusion were significantly decreased.Yet in IPC＋St.Ⅱ group the recovery of CF,HR,LVDP and ±dp/ dtmax was significantly improved compared with CONⅡ and less CK-MB leaked out and as well as preserved myocardial ATP content.Conclusion：Single IPC can not bring forth cardioprotectection on immature rabbit hearts experiencing with global ischemia and reperfusion;on the contrary,it may lead to injury of the myocardium.However under the use of cardioplegia,IPC provides significant cardioprotective effects.Therefore,on the isolated hearts perfused with Langendorff model,this study firstly concluded that the use of cardioplegia is the precondition of IPC-induced cardioprotection.