内源性环氧化酶-2在未成熟心肌缺血预处理延迟保护中对线粒体渗透性转换孔的影响

Effect of Maker Cyclooxygenase-2 and Mitochondrial Permeability Transition Pore on Delayed Protection of Ischemic Pretreament in Immature Myocardium

目的研究环氧化酶-2(COX-2)在未成熟心肌缺血预处理延迟保护中的作用,并观察COX-2对心肌线粒体渗透性转换孔的影响。方法取中国大白兔36只,随机分为以下6组,I(假手术)组、Ⅱ(缺血/再灌注)组、Ⅲ(缺血预处理)组、Ⅳ(缺血预处理+二甲亚砜)组、Ⅴ(缺血预处理+NS-398)组、Ⅵ(缺血预处理+Atr)组,分别于预处理24h后行心肌缺血30 min,再灌注1 h,观察左室发展压(LVDP)、左室压上升及下降最大速率(+dp/dtmax,-dp/dtmax)变化、肌酸激酶(CK)、乳酸脱氢酶活性(LDH)、丙二醛(MDA)含量;采用分光光度法观察COX-2对缺血心肌线粒体渗透性转换孔的影响。结果缺血再灌注1 h后,Ⅱ、Ⅴ、Ⅵ组LVDP、±dp/dtmax值均明显低于Ⅲ、Ⅳ组,Ⅳ组明显高于Ⅱ、Ⅴ、Ⅵ组,差异均有统计学意义(P<0.05或<0.01);Ⅱ、Ⅴ、Ⅵ组CK、LDH、MDA均较Ⅲ组明显升高(P<0.05);在心肌缺血24h后,COX-2可减轻线粒体肿胀,该作用可被苍术苷或NS-398取消。结论缺血预处理产生的COX-2对缺血再灌注损伤具有延迟保护作用,其机制可能与抑制线粒体渗透性转换孔的开放有关。

Objective To investigate the effect of cyclooxygenase-2 （COX-2） and mitochondrial permeability transition pore in the heart of immature rabbit during the late phase of ischemic preconditioning. Methods Thirty six China white rabbits （aged 2 to 3 weeks） were randomly di- vided into 6 groups （n=6）： Group Ⅰ： normal control ; Group Ⅱ： ischemic/ reperfusion（I/R）;GroupⅢ： I/R after ischemic pretreatment（IP）; GroupⅣ： I/R after IP adding DMSO（the solvant of NS-398）; Group Ⅴ： I/R after IP adding NS-398（the COX-2 inhibitor）; Group Ⅵ： I/R after IP adding atracty- loside （the opening of mitochondrial permeability transition pore）. The changes in LVDP and ±dp/ dtmax in left ventricle were monitored with Maclab/8s system. The activity of LDH,CK from plasm was assayed and the content of MDA in plasma was detected. The swelling of mitochondria isolated from ischemic myocardium was evaluated by spectrophotometry. All methods mentioned above were used to evaluate effect of COX-2 and mitochondrial permeabi!ity transition pore on delayed protection of ischemic pretreament in immature myocardium. Results After one hour of reperfusion, the recovery rate of LVDP,±dp/dtmax in group Ⅲ and Ⅳ ,were significantly higher than those in others groups respectively（P〈0.01）. The activity of LDH and CK in plasma in group Ⅱ,ⅤandⅥ were higher than those in group Ⅲ （p〈0.05）. COX-2 significantly decreased the swelling of the ischemic immature myocardium mitochondria induced by calcium overload, which was abolished by atractyloside. Conclusion COX-2 mediates the cardioprotective effects of the late phase of ischemic preconditioning in immature myocardium of rabbits. Activation of COX-2 by IP may be one of the mechanisms which inhibit the opening of mitochondrial permeability transition pore.