St.Thomas NO.2停跳液与含血心肌停跳液对未成熟兔心肌的保护作用

比较观察St.ThomasNO .2停跳液与含血心肌停跳液对未成熟兔心肌的保护作用 ,以期为未成熟心肌保护的临床应用找到一种更有效的方法。选用生后 14～ 2 1天新西兰兔 12只 ,在改良的Langendorff模型上 ,对St.ThomasNO .2停跳液及含血心肌停跳液分别进行低温缺血再灌注离体心脏实验。观察缺血前后心功能变化 (左心室最大压力变化速率、左心室搏出功、左心室搏出功指数及心输出量等指标 )、心肌含水率及心肌酶学的变化。结果发现 ,离体心脏缺血再灌后 ,含血心肌停跳液组左心室最大压力变化速率、左心室搏出功、左心室搏出功指数和心输出量等心功能指标恢复明显好于St.ThomasNO .2停跳液组 (P <0 .0 5 ) ;含血心肌停跳液组心肌肌酸激酶及乳酸脱氢酶漏出率与St.ThomasNO .2停跳液组相比明显降低 (P <0 .0 5 ) ;但两组心肌含水率无明显差异。结果提示 ,初步证实含血心肌停跳液对未成熟心肌的心肌保护效果比St.ThomasNO .2停跳液效果好     

模拟缺血-再灌注对窦房结细胞起搏离子流的影响及K_(ATP)通道开放剂的干预作用

探讨模拟缺血 再灌注对窦房结细胞起搏离子流 (If)的影响及KATP通道开放剂Pinacidil的干预效果。分离乳鼠窦房结细胞 ,纯化培养 2天后进行实验。随机分为对照组、模拟缺血 再灌注组 (I/R)、KATP通道开放剂Pinacidil干预组 (P +I/R)及KATP通道阻断剂 5 HD干预组 (5 HD +P +I/R及 5 HD +I/R)。采用常规全细胞膜片钳技术及多导管灌流系统 ,测定各组细胞If 密度 ,并绘制If 激活曲线。结果 :①每个窦房结细胞均可记录到If 电流 ,在相同指令电压下 ,I/R组窦房结细胞If 密度值较对照组明显增加 (P <0 .0 1) ;而P +I/R组则较I/R组显著减小 (P <0 .0 1) ;5 HD +P +I/R及 5 HD +I/R两组又较P +I/R组明显增加 (P <0 .0 1) ,但与I/R组比较无显著差异。②与对照组比较 ,I/R组窦房结细胞的If 激活曲线发生右移 ,半数最大激活电压由 - 10 8.0± 12 .4mV变为 - 89.5± 7.2mV(P <0 .0 1) ;P +I/R组窦房结细胞If 激活曲线较I/R组左移 ,半数最大激活电压为 - 99.5± 10 .8mV(P <0 .0 5 ) ;KATP通道阻断剂 5 HD可阻断Pinacidil对If 激活曲线的影响。结论 :KATP通道开放剂Pinacidil可对抗模拟缺血 再灌注对窦房结细胞If 的影响 ,此有利于维持模拟缺血 再灌注时窦房结细胞离子稳态和电生理活动的相对稳定     

黄芪注射液加强心肌保护液在兔未成熟心肌保护作用的研究

目的探讨黄芪注射液加强心肌保护液对未成熟兔心肌的保护作用。方法 24只幼兔(兔龄14 d~21 d)随机分3组,每组8只。用Langendorff模型灌注离体心脏。平稳灌注45 min后,主动脉根部灌注STH液(4℃)。对照组(Con):灌注STH液;黄芪组(AS):黄芪注射液+STH灌注;5羟葵酸液(5-HD)组:5-HD+STH灌注。3组心脏均经历停灌30 min(保温、保湿)及再灌注40 min复制模型。观察3组的血流动力学、心肌酶、冠脉流出液、病理学变化、心肌能量变化及分子生物学改变。结果黄芪组左心功能、冠脉流量恢复及再灌后心肌组织内ATP含量明显优于对照组及5-HD组,心肌酶值明显低于对照组及5-HD组,心肌细胞线粒体超微结构分析显示预处理组线粒体损伤轻于对照组及5-HD组,心肌诱导型一氧化氮合酶(iNOS)AS组78.4 ng,高于对照组20.8 ng及5-HD组61.8 ng。结论黄芪加强心肌保护液对兔未成熟心肌有保护作用,黄芪可能是KATP通道开放剂。     

葡萄糖、1，6－二磷酸果糖对心肌保护作用的实验研究

本实验采用离体鼠心模型证实，用含葡萄糖的停跳液单次灌注心脏，心肌组织乳酸产生增加，引起心肌组织酸中毒，心肌结构破坏严重，心功能恢复差，心肌酶漏出较多。而用分别含有葡萄糖和１．６—二磷酸果糖的停跳液多次灌注心脏的两个组，能及时将乳酸冲洗掉。防止了心肌酸中毒，心肌结构损伤减轻，心功能恢复改善，心肌酶漏出较少。研究表明在停跳液中加入葡萄糖、１．６─二磷酸果糖并结合多次灌注方法，能改善心肌保护的效果。     

Diazoxide对乳鼠窦房结细胞模拟缺血-再灌注时的保护作用研究

目的为探讨KATP通道开放剂Diazoxide对模拟缺血-再灌注时培养乳鼠窦房结细胞的保护作用及其可能机制.     

葡萄糖,1,6—二磷酸果糖对心肌保护使用的实验研究

本实验采用离体鼠心模型证实，用含葡萄糖的停跳液单次灌注心脏，心肌组织乳酸产生增加，引起心肌组织酸中毒，心肌结构破坏严重，心功能恢复差，心肌酶漏出较多。而用分别含有葡萄糖和１．６－二磷酸果糖的停跳液多次灌注心脏的两个组，能及时乳时将乳酸冲洗掉。防止了心肌酸中毒，心肌结构损伤减轻，心功能恢复改善，心肌酶漏出较少。研究表明在停跳液中加入葡萄糖，１．６－二磷酸果糖并结合多次灌注方法，能改善心肌保护的效果。     

血管紧张素Ⅱ预处理对体外大鼠缺血再灌注心肌的保护作用

目的 :研究血管紧张素Ⅱ (AngⅡ )预处理是否对缺血 /再灌注 (I/R)心肌有保护作用 ,其作用是否通过蛋白激酶C(proteinkinaseC ,PKC)及线粒体ATP依赖性钾通道 (KATP)而起作用。方法 :4 0只SD大鼠 ,随机分为 5组 (每组各 8只 ) :AngⅡ预处理组 (APC组 )、缬沙坦加AngⅡ预处理组 (VAPC组 )、PKC阻滞剂chelerythine加AngⅡ预处理组 (CLT组 )、线粒体KATP通道阻滞剂 5 Hydroxydecanoate加AngⅡ预处理组 (5 HD组 )和对照组(C组 )。应用Langendorff主动脉逆行灌流的体外大鼠I/R心脏模型 ,观察各组大鼠I/R后心肌细胞乳酸脱氢酶(LDH)及肌酸激酶 (CK)漏出率、心肌组织三磷酸腺苷 (ATP)含量及心功能指标 (LVSP与±dp/dtmax)。结果 :APC组CK、LDH漏出率较C组明显减少 (P <0 .0 1) ,心肌ATP含量较C组增加 (P <0 .0 1) ,心功能 (LVSP与±dp/dtmax)较C组改善。VAPC组、CLT组及 5 HD组上述各指标 (LDH、CK、ATP、LVSP及±dp/dtmax)分别与C组相应的各指标比较差异无统计学意义 (P >0 .0 5 )。结论 :AngⅡ预处理对I/R心肌有保护作用     

三磷酸腺苷敏感性钾通道开放剂对模拟缺血/再灌注乳鼠窦房结细胞内钙及L-型钙电流的影响

通过观察三磷酸腺苷敏感性钾通道(KATP)开放剂对模拟缺血/再灌注(I/R)时乳鼠窦房结细胞内Ca2+及ICaL的影响,探讨模拟缺血预适应(IP)对模拟I/R时窦房结细胞的保护机制。取培养2天的乳鼠窦房结细胞,随机分为①对照组;②模拟I/R组;③模拟IP组;④Diazoxide(线粒体KATP开放剂)+模拟I/R组;⑤5HD(线粒体KATP阻断剂)+模拟IP组。以免疫荧光技术标记细胞内Ca2+,通过激光共聚焦显微镜检测荧光强度变化;以全细胞膜片钳技术检测ICaL。结果:①Diazoxide预处理能模拟IP效应,显著降低I/R后窦房结细胞内Ca2+荧光强度(P<0.01),增加相应电压下的ICaL电流密度,使电流电压曲线相对下移。②5HD预处理阻断了IP效应,其窦房结细胞内Ca2+荧光强度及ICaL电流密度与I/R组接近。结论:KATP开放剂预处理能模拟IP效应,减轻模拟I/R引起的窦房结细胞内Ca2+超载,改善受抑的ICaL。     

钾离子通道开放剂对未成年兔心肌的保护作用

目的：探讨钾离子通道开放剂对未成年兔心肌缺血再灌注损伤的保护作用。方法：在改良Ｌａｎｇｅｎｄｏｒｆ模型上,对Ｓｔ．Ｔｈｏｍａｓ液（Ｓ组）及用１０μｍｏｌ／ＬＮｉｃｏｒａｎｄｉｌ强化的Ｓｔ．Ｔｈｏｍａｓ液（Ｓ＋Ｎ组）两种停跳液进行低温缺血再灌注离体心脏实验。观察缺血前、后心功能变化（左心室变化压、左心室舒张末压、最大压力变化速率、心肌含水量及冠状动脉流量等指标）。结果：离体心脏缺血再灌注后,Ｓ＋Ｎ组左心室变化压、左心室舒张末压、最大压力变化速率及冠状动脉流量等指标方面恢复明显好于Ｓ组。结论：Ｎｉｃｏｒａｎｄｉｌ作为新的有效的停跳液成分,可增强Ｓｔ．Ｔｈｏｍａｓ对未成年兔心肌的保护作用。     

钾离子通道开放剂对老年大鼠心肌保护作用的实验研究

目的 :探讨钾离子通道开放剂 (Nicorandil)对老年大鼠心肌缺血再灌注损伤的保护作用。方法 :在老年大鼠离体心脏的改良工作模型上 ,观察St.Thomas液 (S组 )、含 2 0 μmol/L钾离子通道开放剂Nicorandil的超极化停搏液 (N组 )和Nicorandil强化的St.Thomas液 (S +N组 )对老年大鼠进行低温缺血再灌注后的保护效果。结果 :缺血再灌注 30min后冠脉流量 (CF)恢复百分率、左室压力微分 (±dp/dt)及收缩压、舒张压恢复百分率S +N组明显优于S、N组 (P <0 0 5 ) ;灌注停跳液后心肌电活动和机械活动的消失时间S组少于N、S +N组 (P <0 0 1) ;再灌注后乳酸脱氢酶 (LDH)、磷酸肌酶同工酶(CK MB)漏出量及心肌含水量 3组间无明显差异。结论 :Nicorandil可增强老年大鼠心肌在缺血再灌注后的左室功能恢复 ,但延长心肌电、机械活动消失时间。因此 ,它对老年心肌的保护作用尚有待进一步研究。     

后适应在兔心肌缺血再灌注损伤中的实验研究

目的：观察缺血后适应对兔心肌缺血再灌注损伤（IRI）的保护作用。方法将30只新西兰大白兔随机分为缺血-再灌注组（IR组）,缺血后适应组,后适应加5-羟基癸酸盐（5-HD）组,延迟后适应组及假手术组5组,每组6只。采用硫代巴比妥酸比色法检测5组大白兔心肌组织丙二醛含量,依文思兰加氯化四氮唑兰双重染色法及称重法测定心肌梗死范围大小。结果丙二醛含量缺血后适应组显著低于IR组和延迟后适应组（均P＜0.01）,与后适应加5-HD组相近,但显著高于假手术组（P＜0.05）。心肌梗死面积在IR组、后适应加5-HD组、延迟后适应组之差异无统计学意义（P＞0.05）,但大于缺血后适应组,差异均有显著统计学意义（均P＜0.01）。结论缺血后适应在兔心肌IRI模型中有明显的心肌保护作用;特异性线粒体ATP敏感钾通道抑制剂5-HD可完全取消后适应的心肌保护作用;延迟5min后实行后适应操作其保护作用完全消失。     

K_(ATP)通道开放剂对模拟缺血-再灌注时培养乳鼠窦房结细胞的保护作用及机制探讨

为探讨三磷酸腺苷敏感性钾通道 (简称KATP通道 )开放剂对模拟缺血 再灌注时培养的乳鼠窦房结细胞的保护作用及其可能机制。分离乳鼠窦房结细胞 ,纯化培养 2天后进行实验。随机分为对照组、模拟缺血 再灌注组 (I/R组 )、KATP通道开放剂Pinacidil干预组 (P +I/R组 )及KATP通道阻断剂干预组 (5 HD +P +I/R组与 5 HD +I/R组 )。以流式细胞术检测各组窦房结细胞存活率 ;用激光共聚焦显微镜测定各组窦房结细胞内钙。结果 :①I/R组窦房结细胞存活率 (51 .79%± 6 .2 8% )较对照组 (95 .0 8%± 1 0 .48% )明显降低 (P <0 .0 0 1 ) ;P +I/R组 (63 .77%± 5 .35 % )则较I/R组显著增加 (P <0 .0 1 ) ;而 5 HD +P +I/R组 (52 .88%± 6 .2 5 % )及 5 HD +I/R组 (53 .1 6 %± 5 .35 % )均较P +I/R组明显降低 (P <0 .0 1 )。②以对照组窦房结细胞平均荧光强度值为 1 0 0 % ,其余各组窦房结细胞相对荧光值为 :I/R组 374%± 52 % ,显著高于对照组 (P <0 .0 1 ) ;P +I/R组 1 62 %± 2 0 % ,较I/R组显著降低 (P <0 .0 1 ) ;5 HD +P +I/R及 5 HD +I/R两组分别为 385 %± 56 %与 379%± 44 % ,均较P +I/R组显著增高 (P <0 .0 1 )。结论 :①模拟缺血 再灌注可显著降低窦房结细胞存活率 ,并致窦房结细胞内钙超载 ;②KATP通道     

Roles of mitochondrial ATP-sensitive K channels and PKC in anti-infarct tolerance afforded by adenosine A1 receptor activation

OBJECTIVES: This study intended to assess the role of mitochondrial ATP-sensitive potassium (mitoK ATP) channels and the sequence of signal transduction with protein kinase C (PKC) and adenosine A1 receptors in rabbits. BACKGROUND: To our knowledge, the link between trigger receptors of preconditioning, PKC and mitoK ATP channels has not been examined in a whole heart model of infarction. METHODS: In the first series of experiments, myocardial infarction was induced in isolated buffer-perfused rabbit hearts by 30-min global ischemia and 2-h reperfusion. Infarct size in the left ventricle was determined by tetrazolium staining and expressed as a percentage of area at risk (i.e., the whole left ventricle) (%IS/AR). In the second series of experiments, mitochondria were isolated from the heart, and their respiratory function was examined using glutamate as a substrate. RESULTS: Pretreatment with R-phenylisopropyladenosine (R-PIA, 1 micromol/liter), an A1-receptor agonist, reduced %IS/AR from 49.8 +/- 6.5% to 13.4 +/- 2.9%. This protection was abolished by calphostin C, a PKC inhibitor, and by 5-hydroxydecanoate (5-HD), a selective inhibitor of mitoK ATP channels. A selective mitoK ATP channel opener, diazoxide (100 micromol/liter), mimicked the effect of R-PIA on infarct size (%IS/AR = 11.6 +/- 4.0%), and this protective effect was also abolished by 5-HD. However, calphostin C failed to block the infarct size-limiting effect of diazoxide. Neither calphostin C nor 5-HD alone modified %IS/AR. State III respiration (QO2) and respiratory control index (RCI) were reduced after 30 min of ischemia (QO2 = 147.3 +/- 5.3 vs. 108.5 +/- 12.3, RCI = 22.3 +/- 1.1 vs. 12.1 +/- 1.8, p < 0.05). This mitochondrial dysfunction was persistent after 10 min of reperfusion (QO2 = 96.1 +/- 15.5, RCI = 9.5 +/- 1.9). Diazoxide significantly attenuated the respiratory dysfunction after 30 min of ischemia (QO2 = 142.8 +/- 9.7, RCI = 16.2 +/- 0.8) and subsequent 10-min reperfusion (QO2 = 135.3 +/- 7.2, RCI = 19.1 +/- 0.8). CONCLUSIONS: These results suggest that mitoK ATP channels are downstream of PKC in the mechanism of infarct-size limitation by A1-receptor activation and that the anti-infarct tolerance afforded by opening of mitoK ATP channels is associated with preservation of mitochondrial function during ischemia/reperfusion.     

Adenosine triphosphate-sensitive potassium channel blocking agent ameliorates,but the opening agent aggravates,ischemia/reperfusion-induced injury: Heart function studies in nonfibrillatingt isolated hearts

Objectives. This study was conducted to elucidate the role of the adenosine triphosphate (ATP)-sensitive potassium channel blocking agent glibenclamide and the opener cromakalim in the mechanism of reperfusion-induced injury.Background. Recently, ATP-sensitive potassium channel openers have been proposed to reduce ischemia/reperfusion-induced injury, including arrhythmias and heart function. Thus, one night hypothesize that pharmacologic agents that enhance the loss of potassium ions in the myocardium through ATP-sensitive potassium channels would be arrhythmogenic, and agents that interfere with tissue potassium ion loss would be antiarrhythmic.Methods. Isolated “working” guinea pig hearts and phosphorus-31 nuclear magnetic resonance spectroscopy were used to study the recovery of myocardial function and phosphorus compounds after 30, 40 and 50 min of normothermic global ischemia followed by reperfusion in untreated control and glibenclamide-and cromakalim-treated groups.Results. After 30 min of ischemia, 1, 3, 10 and 30 μmol/liter of glibenclamide dose-dependently reduced the incidence of reperfusion-induced ventricular fibrillation (total) from its control value of 92% to 75%, 33% (p < 0.05), 33% (p < 0.05) and 42% (p < 0.05), respectively. The incidence of ventricular tachycardia followed the same pattern. A reduction of arrhythmias was also observed after 40 and 50 min of ischemia followed by reperfusion in the glibenclamide-treated hearts. Cromakalim, at the same concentrations, did not reduce the incidence of reperfusion-induced arrhythmias. During reperfusion, glibenclamide (3 and 10 μmol/liter) improved the recovery of coronary blood flow, aortic low, myocardial contractility and tissue ATP and creatine phosphate content, but cromakalim failed to ameliorate the recovery of postischemic myocardium compared with that in the drug-free control hearts.Conclusions. The preservation of myocardial potassium ions and phosphorus compounds by glibenclamide can improve the recovery of postischemic function, but the use of ATP-sensitive potassium channel openers as antihypertensive or antiarrhythmic agents may be of particular concern in those postinfarction patients who are known to be at high risk for sudden cardiac death.     

Mitochondrial K<Subscript>ATP</Subscript> channel-dependent and -independent phases of ischemic preconditioning against myocardial infarction in the rat

To obtain insight into the role of the mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channel in ischemic preconditioning (PC), we aimed to clarify the mitoK(ATP) channel-dependent phase of PC in two PC protocols with different intervals between PC ischemia and an index ischemia. The possible contribution of mitoK(ATP) channel opening to protein kinase C activation in PC was also examined by Western blotting. Myocardial infarction was induced by 30-min coronary occlusion/2-h reperfusion in rat hearts in situ, and infarct size was expressed as a percentage of the area at risk (% IS/AR). PC was performed with 2 episodes of 5-min ischemia, and each heart was subjected to 30-min ischemia either 5 min or 20 min after PC. At 5 min after PC, both PKC-delta and -epsilon were translocated and the myocardium was protected against infarction (% IS/AR = 28.3 +/- 2.7 % vs. 72.7 +/- 2.2 in controls p < 0.05). Pretreatment with a selective mitoK(ATP) channel blocker, 5-hydroxydecanoate (5-HD, 10 mg/kg), abolished the cardioprotection but not PKC translocation by PC. At 20 min after PC, PKC translocation remained at the same level as that 5 min after PC, but the anti-infarct tolerance was attenuated (%IS/AR = 43.5 +/- 4.7 %). Injection of 5-HD after PC did not affect anti-infarct tolerance at 5 min after PC but abolished the protection at 20 min after PC without any effects on PKC. These results suggest that the mitoK(ATP) channel plays a role in triggering of PC in a PKC-independent manner and that the role of the mitoK(ATP) channel as a mediator of protection is detectable after, but not before, the PC effect starts to decay without a change in the level of PKC translocation in the rat heart.     

Cardioprotective effects of 17 beta-estradiol produced by activation ofmitochondrial ATP-sensitive K(+)Channels in canine hearts

We have previously demonstrated the effects of estrogen on modulation of myocardial ATP-sensitive K(+)(K(ATP)) channel. Previous studies have demonstrated that activation of mitochondrial K(ATP)channel is a major contributor of ischemic cardioprotection. The purpose of the present study was to investigate the role of K(ATP)channel in estrogen-induced myocardial protection after ischemia/reperfusion in dogs. Anaesthetized dogs were subjected to 60 min of left anterior descending coronary artery occlusion followed by 2 h of reperfusion. In a first study to characterize effects of sex and the dose-response profile of estrogen on infarct size, the drug was intravenously administered at 10 or 20 microg/kg. In a second study to investigate the cardioprotective mechanisms of estrogen, vehicle, preconditioning or 17 beta -estradiol (10 microg/kg) was given, beginning 15 min prior to the 60 min occlusion period in the presence or absence of 5-hydroxydecanoate (5-HD). In the first study, administration of 17 beta -estradiol resulted in a significant, dose-dependent limitation of infarct size. Estrogen administration provided myocardial protection of similar magnitude in both males and females. In the second study, infarct size in control animals averaged 39+/-5% of the risk region, compared with 14+/-5% of the risk region in estrogen-treated dogs and 6+/-5% of the risk region in preconditioning dogs (both P<0.0001 v controls). Pretreatment with 5-HD completely abolished preconditioning- and estrogen-induced cardioprotection. Estrogen limits myocardial infarction size resulting from coronary artery occlusion and reperfusion in a dose-dependent fashion, irrespective of gender difference. The infarct size-limiting effect of estrogen++ was abolished by 5-HD, suggesting that the cardioprotective effect of estrogen may result from activation of myocardial mitochondrial K(ATP)channels.     

庚醇预处理的心脏保护作用对细胞膜缝隙连接蛋白43的影响

目的探讨庚醇预处理对家兔心肌缺血再灌注损伤的作用及其机制。方法将50只新西兰大白兔随机分为5组:假手术组、缺血再灌注组(IR组)、缺血预处理组(IP组)、庚醇预处理组(HP组)、庚醇预处理加5-羟葵酸(5-HD)预处理组(HP+5-HD组),每组10只。所有新西兰大白兔再灌注4h后处死。分别于术前、缺血时、再灌注2、4h检测血浆肌酸激酶同工酶和心肌肌钙蛋白活性;采用免疫荧光标记检测Cx43。结果与IR组比较,IP组及HP组心肌坏死区/左心室范围明显降低(P<0.01)。与假手术组比较,IR组、HP+5-HD组Cx43mRNA表达明显降低(P<0.01);与HP+5-HD组比较,IP组、HP组Cx43mRNA表达明显升高(P<0.01);与IR组比较,IP组、HP组、HP+5-HD组Cx43mRNA表达明显升高(P<0.05,P<0.01)。结论庚醇预处理可以通过衰减由心肌缺血再灌注诱导的细胞膜Cx43表达下降,对损伤心肌起到保护作用。     

线粒体KATP在阿托伐他汀心功能保护效应中的作用

目的观察阿托伐他汀（ATV）对心肌缺血/再灌注损伤的影响以及线粒体ATP敏感性钾通道（mitoKATP）在其中的作用。方法将兔随机分成缺血/再灌注模型对照组（control组）、ATV组、ATV+5-羟癸酸（5-HD）组、5-HD组。进行40min局部缺血和240min再灌注,观察各组血流动力学、血液生物化学、线粒体ATP合成能力（[ATP]m）。结果缺血/再灌注使左室发展压（LVDP）和压力上升最大速率（+dp/dtmax）均显著下降（均P<0.01）;3dATV10mg/（kg·d）预处理使缺血/再灌注后LVDP和+dp/dtmax的下降幅度显著降低（均P<0.01）,并且降低CK-MB和LDH-1、提高[ATP]m;ATV+5-HD组LVDP和+dp/dtmax的下降幅度、CK-MB、LDH-1、[ATP]m均和对照组无明显差异。结论ATV预处理通过激活mitoKATP改善缺血/再灌注后左室收缩功能,mitoKATP是KATP途径的主要作用位点。     

Mitochondrial K(ATP) channel as an end effector of cardioprotection during late preconditioning: triggering role of nitric oxide.

Nitric oxide (NO) has been implicated in the "second-window" of ischemic preconditioning (PC). However, the identity of the end effector after initiation of preconditioning by NO is not known. It is likely that NO is involved in opening of mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels. We hypothesized that NO is an important trigger for the opening of mitoK(ATP) channels in the late phase of preconditioning and inducible nitric oxide synthase (iNOS) up-regulation via NF kappa B plays a critical role in diazoxide-induced cardioprotection. To examine this, diazoxide (7 mg/kg) was administered to wild-type (WT) mice and mice lacking the gene 24 hours before 40 minutes of global ischemia. Hearts were perfused in a Langendorff mode and effects of activation of mitoK(ATP) channel and other interventions on functional, biochemical and pathological changes in ischemic hearts were assessed. In hearts from WT mice treated diazoxide, left-ventricular-developed pressure, end-diastolic pressure and coronary flow were significantly improved after ischemia/reperfusion (I/R); lactate dehydrogenase (LDH) release was also significantly decreased, while ATP contents were significantly higher. Administration of 5-HD, a specific blocker of mitoK(ATP) channel or l -NAME, an inhibitor of iNOS before I/R, during diazoxide-pretreatment completely blocked the late cardioprotection against ischemia. Late cardioprotection was also blocked by inhibition of either PKC- delta by rottlerin or NF kappa B by DDTC before diazoxide pretreatment. Diazoxide pretreatment significantly increased nuclear translocation of p65 which was blocked by protein kinase C (PKC) or nitric oxide synthase (NOS) inhibition. Diazoxide was totally inefffective in iNOS knockout mice. These results suggest that diazoxide activates NF kappa B via PKC signaling pathway and that leads to iNOS up-regulation after 24 hours. NO which is generated upon ischemic stress triggers the opening of mitoK(ATP)channel as an end effector of cardioprotection during late PC.