诱导型一氧化氮合酶与环氧化酶-2在未成熟心肌缺血预处理延迟性保护机制中的关系

Effect of inducible nitric oxide synthase and cyclooxygenase-2 on delayed protection of ischemic precondtioning in immature myocardium

目的 探讨诱导型一氧化氮合酶 (iNOS)与环氧化酶 - 2 (COX - 2 )在未成熟兔心肌缺血预处理延迟性保护机制中的关系。方法 健康 2～ 3周中国大白兔 36只 ,随机分为 6组 :假手术组 (Ⅰ组 ) ,缺血再灌注组 (Ⅱ组 ) ,缺血预处理组 (Ⅲ组 ) ,缺血预处理 +二甲亚砜组 (Ⅳ组 ) ,缺血预处理 +NS - 398组 (Ⅴ组 )和缺血预处理 +14 0 0W组 (Ⅵ组 ) ,每组 6只。分别于预处理 2 4h后行心肌缺血 30min ,再灌注 6 0min ,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。采用Westernblot及比色法分别测定COX - 2蛋白活性及iNOS活性。结果 缺血再灌注 1h后Ⅱ、Ⅴ、Ⅵ组LVDP、+dp dtmax、-dp dtmax恢复率均显著低于Ⅲ组 (P <0 .0 1) ,Ⅲ、Ⅳ组LVDP、±dp dtmax恢复率较其他组升高明显 (P <0 .0 1) ;Ⅲ组心肌iNOS活性较Ⅰ及Ⅱ组活性显著升高 (P<0 .0 5 ) ,Ⅴ和Ⅵ组心肌COX - 2蛋白活性较Ⅲ组显著降低 (P <0 .0 5 )。结论 iNOS和COX - 2共同参与了未成熟兔缺血预处理延迟性心肌保护作用 ,COX - 2处于iNOS下游 ,iNOS对COX - 2活性具有调控作用。

Objective To investigate the relationship between inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in the heart of immature rabbit during the late phase of ischemic preconditioning (IP). Methods Thirty six China white rabbits (aged 2 to 3 weeks) were randomly divided into 6 groups (n=6 each group): groupⅠ, normal control; groupⅡ, ischemia/reperfusion injury (I/R); groupⅢ, I/R after IP; groupⅣ, I/R after IP adding DMSO (the solvant of NS-398); groupⅤ, I/R after IP and adding NS-398 (the COX-2 inhibitor); groupⅥ, I/R after IP and adding 1400 w (the iNOS inhibitor). The changes of LVDP and ±dp/dt max in left ventricle were monitored with Maclab/8 s system. COX-2 and iNOS in myocardium were determined. Results After 1 hour of reperfusion, the recovery rates of LVDP, +dp/dt max and -dp/dt max were significantly higher in groupⅢ and Ⅳ than in others groups (P<0.01). Western immunoblotting technique showed the activity of COX-2 was markedly higher in groupⅢ than in groupsⅠ and Ⅱ, and groupsⅤ and Ⅵ(P<0.05). Colorimetric assay revealed the activity of iNOS was also higher in groupⅢ than in the other groups (Ⅰ, Ⅱ, Ⅴ, Ⅵ)(P<0.05). Conclusion Both iNOS and COX-2 are the factors involved in the delayed protection of IP against I/R in immature myocardium. As COX-2 is downstream of iNOS, the latter may modulate the activity of the former.