大鼠心脏缺血-再灌注损伤对心肌L-Arg/NO途径的影响

为探讨大鼠心脏缺血-再灌注损伤(IRI)期间一氧化氮(NO)生成增加的环节和过程。本实验用离体灌流大鼠心脏,预灌流15 min,停灌45 min,取30 ml KH 液循环灌流15 min,观察冠脉流出液中细胞胞浆酶(LDH)、蛋白质、肌红蛋白漏出量和NO     

内源性CO在大鼠离体心脏缺血再灌注中的保护作用

本文旨在观察研究内源性CO在大鼠离体心脏缺血再灌注中的作用。大鼠经内源性CO激动剂原卟啉氯化钴(CoPP)和内源性CO抑制剂锌原卟啉(ZnPP)处理后,采用Langendorff离体心脏灌流系统完成心脏缺血再灌注模型,停灌(缺血)时间设定为30 min,分别采集离体心脏稳定期和再灌注后30 min心功能指标参数,ELISA方法检测心肌组织cGMP含量,比色法测定血浆中内源性CO的含量以及再灌注10 min时灌流液中肌酸激酶(creatine kinase,CK)、乳酸脱氢酶(lactic dehydrogenase,LDH)等心肌酶的指标。结果显示,停灌前离体心脏跳动平稳,CoPP组、ZnPP组和对照组心脏各项功能指标均保持稳定,三组间心功能指标无明显差异;再灌注后,三组间心功能指标出现显著性差异(P0.05),与停灌前相比,对照组和ZnPP组心功能均明显下降(P0.05),且ZnPP组下降较为显著,而CoPP组仍能保持停灌前水平。与此同时,三组大鼠体内CO含量、离体心肌酶学指标和再灌注后恢复稳定时间也有明显的差异(P0.05),和对照组相比,CoPP组复灌稳定恢复时间减少,灌流液中CK和LDH含量显著减少,血浆内源性CO含量和心肌cGMP含量显著增加,而ZnPP组则呈现截然相反的结果。以上结果提示,内源性CO可维持一定的心脏舒缩能力、缩短心脏复跳时间,在心脏缺血再灌注中起到了保护作用。     

黑木耳多糖对抗离体心脏缺血/再灌注损伤的研究

目的:探讨黑木耳多糖(AAP)对离体大鼠心脏缺血/再灌注(I/R)损伤的防护作用及其机制。方法:健康雄性SD大鼠灌胃黑木耳多糖(50,100,200mg/(kg.d))4周后,采用离体心脏Langendorff灌流方法,全心停灌30min,复灌120min建立I/R模型。测定左心室动力学指标和再灌注各时间点冠脉流出液中乳酸脱氢酶(LDH)含量;实验结束测定心肌组织甲月赞(formazan)、丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性的变化。结果:与单纯I/R组相比,AAP预处理明显提高心肌细胞的formazan含量,降低再灌注期间冠脉流出液中LDH含量,明显增强左室发展压、左心室内压最大上升速率和心率与发展压乘积的恢复,缓解冠脉流量的减少;高剂量AAP改善I/R心肌功能的作用要好于丹参预处理(4ml/(kg.d),gastricperfusion)组。中剂量AAP(100mg/(kg.d))预处理4周后明显抑制I/R心肌MDA的增加和SOD活性的减弱(P0.01),其效果要好于丹参阳性对照组。结论:在大鼠离体心脏灌流模型上,黑木耳多糖预处理具有抗心脏I/R损伤的作用,这种保护作用可能与其增加心肌SOD活性,减少脂质过氧化损伤有关。     

不同剂量维拉帕米和普奈洛尔钾停搏液对幼大鼠心功能影响

目的观察含不同剂量维拉帕米和普奈洛尔的钾停搏液对未成年缺血心脏保护效应并与高钾停搏液比较,探讨适宜剂量.方法幼大鼠离体心脏Langendorff法灌流,分6组(n=8)正常组(CON)连续灌流170 min;缺血-复灌组(I-R)灌流(稳定)20min,无糖不充氧台氏液灌3 min停灌27 min连续3阵(缺血90 min),恢复正常灌流(复灌)60min;高钾停搏液(ST)和低(L)、中(M)、高(H)剂量"钾维普"保护组缺血期每阵3 min灌注用不含(ST)和含维拉帕米、普奈洛尔(×10-7mol·L-1)分别为2.0、0.34(L),6.8、1.1(M),20、3.4(H)的ST.Thomas Ⅱ号停搏液.实验过程实时动态检测心肌张力、心率、收缩力、最大收缩和舒张速度、冠脉流量、复搏时间评价,心功能.结果CON组灌流150 min心脏张力稳定,心功能降低;与CON组相比,I-R组缺血40 min后心脏挛缩,复灌后张力高,心搏功能丧失;ST组缺血60 min心肌张力升高,复灌后心功能减弱.与ST组相比,L、M、H"钾维普"呈剂量依赖性降低缺血心肌张力,复灌后心搏强;H组复搏延迟.与CON组相比,L组缺血60 min心脏张力升高,复灌后心搏弱;H组缺血40 min心脏张力低,但复灌后心搏弱;M组缺血90 min心脏张力稳定,复灌后心功能好,心搏幅度超过稳定值.结论含维拉帕米6.8×10-7mol·L-1、普奈洛尔1.1×10-7mol·L-1的钾停搏液保护常温缺血90 min幼大鼠心脏效果最佳.     

缺血预处理对缺血/再灌注离体心脏的保护作用

目的：探讨连续多次短暂缺血预处理对缺血/再灌注损伤心肌的保护作用及机制。方法：采用大鼠离体心脏Lan-gendorff灌流模型,观察缺血预处理对心肌缺血/再灌注后不同时间点冠脉流出液中AST、CPK、UDH及冠脉流量,心肌组织中SOD、LPO以及再灌注性心律失常的影响。结果：缺血预处理可以减少缺血/再灌注损伤的心肌冠脉流出液中AST、CPK、LDH的含量,提高心肌SOD活性,降低LPO水平,并且抑制再灌注性心律失常的发生,提高再灌注期间的冠脉流量。结论：缺血预处理对心肌缺血/再灌注损伤具有一定保护作用。     

活性氧、NO和线粒体ATP敏感钾通道在TNF-α预处理对缺血/再灌注心肌保护中的作用

目的: 观察TNF-α预处理对缺血/再灌注心脏功能和酶学指标的影响及其可能机制.方法: 采用心脏Langendorff灌流模型.结果:与单独缺血/再灌注组相比,TNF-α(104U/L)预处理明显减弱缺血/再灌注对左室发展压、左室舒张末压、最大收缩/舒张速率和左室发展压与心率乘积的抑制作用(P<0.05),并显著降低复灌后冠脉流出液中乳酸脱氢酶(LDH)含量,增加线粒体中锰超氧化物歧化酶(Mn-SOD)活性(P<0.05);分别使用抗氧化剂2-MPG(0.3 mmol/L)、一氧化氮合酶抑制剂L-NAME(0.5 mmol/L)或线粒体ATP敏感钾通道抑制剂5-HD(100 μmol/L)预处理,减弱了TNF-α改善缺血/再灌注后心功能、抑制心肌LDH释放和诱导Mn-SOD活性增高的作用.结论: TNF-α预处理具有减轻心脏缺血/再灌注损伤的作用,这一作用可能与其诱导Mn-SOD活性增高有关,活性氧、一氧化氮和线粒体ATP敏感钾通道参与介导TNF-α的心肌保护作用.     

钠泵功能改变及内质网应激在大鼠离体心脏缺血/再灌注损伤中的作用

目的：探讨钠泵活性改变及内质网应激（ERS）在大鼠离体心脏再灌损伤中的作用及其机制。方法：将60只雄性SD大鼠随机分为6组（n=10）：正常对照组（NC组）、缺血/再灌损伤组（I/R组）、哇巴因-缺血/再灌损伤组（OUA-I/R组）、地高辛抗血清-缺血/再灌损伤组（Anti-Dig-I/R组）、Src抑制剂PP2-哇巴因-缺血/再灌损伤组（PP2-OUA-I/R组）、PLC抑制剂U73122-哇巴因-缺血/再灌损伤组（U73122-OUA-I/R组）。建立全心缺血30 min,再灌注120min的Langendorff大鼠离体心脏缺血再灌损伤模型。检测各组相同时间点心功能恢复率、冠脉流出液中乳酸脱氢酶（LDH）和肌酸激酶（CK）活性,心肌中Na⁺-K⁺-ATP酶活性和钙离子水平。流式细胞仪检测心肌细胞凋亡率,Western blot检测心肌钠泵α1亚基、葡萄糖调节蛋白78（GRP78）、C/EBP同源蛋白（CHOP）及凋亡蛋白Bcl-2/Bax的表达。结果：与I/R组相比,给予哇巴因预处理可使心功能恢复率明显下降,心肌酶漏出增多,Na⁺-K⁺-ATP酶的活性降低,心肌细胞内钙水平升高,细胞凋亡率增多,心肌钠泵α1亚基和Bcl-2表达降低,GRP78、CHOP和Bax表达升高;而Anti-Dig-I/R组与I/R组相比各指标均明显改善;给予Src抑制剂PP2或PLC抑制剂U73122后,哇巴因对心肌的损伤作用被部分阻断,表现为心功能恢复率升高,心肌酶漏出减少,Na⁺-K⁺-ATP酶的活性明显恢复,Ca²⁺水平下降,细胞凋亡率下降,心肌钠泵α₁亚基和Bcl-2表达增多,GRP78和Bax表达减少。结论：钠泵功能改变和内质网应激共同参与大鼠离体心脏缺血再灌损伤,钠泵通路（Src和PLC）介导内质网应激是引起大鼠离体心脏缺血再灌损伤细胞凋亡机制之一。     

异丙酚对离体大鼠心肌缺血、再灌注损伤后细胞凋亡及其机制研究

目的：观察异丙酚对离体大鼠心肌缺血/再灌注损伤的影响并从氧化应激和线粒体介导的凋亡方面探讨其作用机制。方法：应用Langendorff离体心脏灌注系统建立心肌缺血/再灌注损伤模型。40只SD大鼠随机分为正常对照组、缺血/再灌注模型（I/R）组、异丙酚15、30、60μmol.L-1组。除正常对照组外,各组分别平衡灌注20 min后,常温全心停灌25 min,再灌注30 min。Powerlab/8s仪记录各组平衡末、缺血前及再灌30 min时的各项心功能指标并测定冠脉流出液中乳酸脱氢酶（LDH）、肌酸激酶（CK）活性;检测心肌线粒体活力、膜肿胀度、锰超氧化物岐化酶（Mn-SOD）活性和丙二醛（MDA）含量;流式细胞仪检测心肌细胞凋亡;流式细胞术检测Bcl-2和Bax的表达,免疫组化法测定天冬氨酸特异的半胱氨酸蛋白酶（caspase）-3,9,8蛋白的表达。结果：与I/R组相比,异丙酚30、60μmol.L-1能明显改善缺血/再灌注后的心功能,减弱冠脉流出液中LDH、CK的活性（P〈0.05）;心肌线粒体活力有所恢复,膜肿胀度减轻,Mn-SOD活性升高,MDA生成明显减少（P〈0.05）,心肌细胞凋亡明显减少,Bcl-2表达上调,Bax表达下调,caspase-3,9阳性表达细胞数明显减少（P〈0.05）。结论：异丙酚明显减轻缺血/再灌注所致的心肌线粒体的过氧化损伤,抑制线粒体途径的凋亡,可能是其心肌保护作用机制之一。     

氯胺酮对大鼠心肌缺血再灌注损伤的保护作用研究

本实验通过构建在体大鼠心肌缺血再灌注损伤(myocardial ischemia-reperfusion injury, MIRI)模型,观察低浓度氯胺酮对该模型大鼠心功能、心电图及其氧化应激反应的影响,探索氯胺酮对心脏MIRI的保护作用效应及其机制。利用BL420S生物信号采集处理系统实时监测记录缺血前10 min给药和缺血30 min后于冠脉再通前给药后大鼠左心室内压等心功能指标及肢体Ⅱ导联心电图,并观察记录心律失常发生情况;实验结束后,TTC染色检测心肌梗死面积;HE染色检测心肌病理形态变化;试剂盒测定血清肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH)活性、肌钙蛋白Ⅰ(c TnⅠ)浓度和心肌组织超氧歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽-过氧化物酶(GSH-Px)活性及丙二醛(MDA)含量。研究结果显示,低剂量氯胺酮能够改善心肌缺血和缺血后再灌注引起的心功能损伤和心电活动紊乱,并降低心律失常的发生率,改善心肌组织病理损伤,降低心肌梗死面积,减少心肌酶的漏出,提高心肌抗氧化能力,抑制活性氧的产生。该研究结果提示,低剂量氯胺酮对MIRI具有保护作用,其机制可能与其抗氧化有关。这为临床寻找预防或减轻心脏手术体外循环恢复供血后的MIRI的解决办法提供了实验数据。     

11,12.环氧二十碳三烯酸预处理与后处理对缺血/再灌注大鼠心肌的保护作用

采用Langendorff离体灌流装置,通过停灌40 min/复灌30 min复制大鼠心肌缺血/再灌注(ischemia/reperfusion,IR)损伤模型,观察11,12-环氧二十碳三烯酸(11,12-epoxyeicosatrienoic acid,11,12-EET)预处理和后处理对心肌线粒体功能以及心功能的影响,探讨11,12-EET顸处理和后处理对IR大鼠心肌的作用及其机制.将30只Sprague-Dawley大鼠随机分为对照组、IR组、EET预处理组(Pre-EET)、EET后处理组(Post-EET),每组6只.除对照组外,其它各组全心缺血40 min,再灌注30 min.监测左心室内压差(ALVP)和左心室内压升降的最大变化率(±dp/dtmax)等心功能指标,测定灌流液中乳酸脱氢酶(1actate dehydrogenase,LDH)的活性.灌流结束后,测定心肌线粒体琥珀酸脱氢酶(succinate dehydrogenase,SDH)、Ca"ATPase、Na - K -ATPase活性以及心肌超氧化物歧化酶(superoxide dismutase,SOD)活性、丙二醛(malondialdehyde,MDA)含量.结果显示:(1)与IR组相比,Pre-EET组及Post.EET组Na -K -ATPase和SDH活性均增强,Ca2 -ATPase活性均减弱,有显著性差异(P<0.05);而Pre-EET与Post-EET组间没有显著性差异.(2)与IR组相比,Pre-EET组及Post-EET组心功能明显改善,LDH漏出显著减少,心肌SOD活性明显增强,MDA含量明显降低,有显著性差异(P<0.05);而Pre-EET与Post-EET组间没有显著性差异.结果表明,11,12-EET预处理及后处理均可通过上调心肌线粒体Na -K -ATPase、SDH活性以及下调Ca2 -ATPase活性改善线粒体功能和心肌能量代谢,拮抗心肌IR损伤;11,12-EET预处理及后处理还可通过提高心肌SOD活性、降低MDA含量改善IR心肌的氧化应激.     

Platelets activated by transient coronary occlusion exacerbate ischemia-reperfusion injury in rat hearts

Platelets (Plt) accumulate in reperfused myocardium but their effect on myocardial necrosis has not been established. We tested the hypothesis that the effect of Plt depends on their activation status. Pig Plt were obtained before 48 min of coronary occlusion (pre-CO-Plt), 10 min after reperfusion (R-Plt), or after a 60-min sham operation (sham-Plt). Plt were infused into isolated rat hearts (n = 124) and subsequently submitted to 60 min of ischemia and 60 min of reperfusion. P-selectin expression was higher (P = 0.02) in R-Plt than in pre-CO-Plt or sham-Plt. Lactate dehydrogenase (LDH) release during reperfusion was similar in hearts receiving pre-CO-Plt, sham-Plt, or no Plt, but R-Plt increased LDH release by 60% (P = 0.004). Activation of pre-CO-Plt with thrombin increased P-selectin expression and LDH release (P < 0.001), and these results were unaffected by tirofiban. There was a close correlation between P-selectin expression and LDH release (r = 0.84; P < 0.001), and myocardial Plt accumulation (r = 0.85; P < 0.001). We conclude that the deleterious effect of Plt on reperfused myocardium depends on their activation status as represented by P-selectin expression, which is enhanced by ischemia-reperfusion.     

Enhanced ADP-ribosylation and its diminution by lipoamide after ischemia-reperfusion in perfused rat heart

Poly-ADP-ribose polymerase (PARP) is considered to play an important role in oxidative cell damage. We assumed that ischemia-reperfusion resulting from the increasing reactive oxygen species (ROS) can lead to the activation of endogenous mono- and poly-ADP-ribosylation reactions and that the reduction of ROS level by lipoamide, a less known antioxidant, can reverse these unfavorable processes. Experiments were performed on isolated Langendorff hearts subjected to 60-min ischemia followed by reperfusion. ROS, malondialdehyde, deoxyribonucleic acid (DNA) breaks, and NAD+ content were assayed in the hearts, and the ADP-ribosylation of cytoplasmic and nuclear proteins were determined by Western blot assay. Ischemia-reperfusion caused a moderate (30.2 +/- 8%) increase in ROS production determined by the dihydrorhodamine 123 method and significantly increased the malondialdehyde production (from < 1 to 23 +/- 2.7 nmol/ml), DNA damage (undamaged DNA decreased from 71 +/- 7% to 23.1 +/- 5%), and NAD+ catabolism. In addition, ischemia-reperfusion activated the mono-ADP-ribosylation of GRP78 and the self-ADP-ribosylation of the nuclear PARP. The perfusion of hearts with lipoamide significantly decreased the ischemia-reperfusion-induced cell membrane damage determined by enzyme release (LDH, CK, and GOT), decreased the ROS production, reduced the malondialdehyde production to 5.5 +/- 2.4 nmol/ml, abolished DNA damage, and reduced NAD+ catabolism. The ischemia-reperfusion-induced activation of poly- and mono-ADP-ribosylation reactions were also reverted by lipoamide. In isolated rat heart mitochondria, dihydrolipoamide was found to be a better antioxidant than dihydrolipoic acid. Ischemia-reperfusion by ROS overproduction and increasing DNA breaks activates PARP leading to accelerated NAD+ catabolism, impaired energy metabolism, and cell damage. Lipoamide by reducing ROS levels halts PARP activation and membrane damage and improves the recovery of postischemic myocardium.     

一氧化氮在铁诱导的大鼠心肌损伤中的作用

采用Langendorff灌流大鼠心脏和酶解分离的心肌细胞为实验模型,研究铁负荷下心肌损伤情况以及一氧化氮（NO）在铁诱导的心肌损伤中的地位。结果显示:（1）心肌铁负荷（Fe-HQ）可使分离心肌细胞舒张期细胞长度缩短、收缩幅度和速度降低,离体灌流心脏左室发展压（LVDP）、±dp/dtmax、冠脉流量呈现双相变化;冠脉流出液中乳酸脱氢酶（LDH）、肌酸激酶（CK）释放量和心肌丙二醛（MDA）增高。（2）NO的前体L-精氨酸（L-argi-nine,L-Arg）引起心肌细胞舒张期细胞长度缩短、收缩幅度降低。离体灌流心脏LVDP、冠脉流量、和±dp/dtmax增高,用K-H液复灌后可恢复正常。（3）L-Arg预处理,再行Fe-HQ灌流,与单纯的L-Arg或Fe-HQ组相比,心肌细胞舒张期细胞长度、收缩幅度和速度减小;离体灌流心脏LVDP、±dp/dtmax、心率和冠脉流量明显下降,冠脉流出液中LDH、CK增加。（4）Nω-硝基-L-精氨酸甲酯（L-NAME）和Fe-HQ合并灌流后,与单纯Fe-HQ组相比,心肌细胞舒张期细胞长度、收缩幅度和速度增加。L-NAME可阻断Fe-HQ引起的LVDP、左室舒张末压（LVEDP）和±dp/dtmax降低,冠脉流出液中LDH、CK增高。（5）用Triton X-100短暂处理以去除冠脉内皮后,与保留冠脉内皮的心肌相比,Fe-HQ引起的LVDP和±dp/dtmax的一过性增高现象被抑制,但     

Effect of ACE inhibitor captopril and L-arginine on the metabolism and on ischemia-reperfusion injury of the isolated rat heart

We investigated the effects of in vivo treatment with the angiotensin-converting enzyme inhibitor (ACE-I) captopril and/or of in vitro administration of L-arginine on the metabolism and ischemia-reperfusion injury of the isolated perfused rat myocardium. Captopril (50 mg/l in drinking water, 4 weeks) raised the myocardial content of glycogen. After 25-min global ischemia, captopril treatment, compared with the controls, resulted in lower rates of lactate dehydrogenase release during reperfusion (8.58 +/- 1.12 vs. 13.39 +/- 1.88 U/heart/30 min, p<0.05), lower myocardial lactate contents (11.34 +/- 0.93 vs. 21.22 +/- 4.28 micromol/g d.w., p<0.05) and higher coronary flow recovery (by 25%), and prevented the decrease of NO release into the perfusate during reperfusion. In control hearts L-arginine added to the perfusate (1 mmol/l) 10 min before ischemia had no effect on the parameters evaluated under our experimental conditions, presumably because of sufficient saturation of the myocardium with L-arginine. In the hearts of captopril-treated rats, L-arginine further increased NO production during reperfusion and the cGMP content before ischemia. Our results have shown that long-term captopril treatment increases the energy potential and has a beneficial effect on tolerance of the isolated heart to ischemia. L-arginine added into the perfusate potentiates the effect of captopril on the NO signaling pathway.     

Intracellular Catalase Inhibition Does not Predispose Rat Heart to Ischemia-Reperfusion and Hydrogen Peroxide-Induced Injuries

The objective of this study was to determine whether inhibition of intracellular catalase would decrease the tolerance of the heart to ischemia-reperfusion and hydrogen peroxide-induced injuries. Isolated bicarbonate buffer-perfused rat hearts were used in the study. Intracellular catalase was inhibited with 3-amino-1,2,4-triazole (ATZ, 1.5 g/kg body weight, two hours prior to heart perfusion). In the ischemia-reperfusion protocol, hearts were arrested with St. Thomas' II cardioplegic solution, made ischemic for 35 min at 37°C, and reperfused with Krebs-Henseleit buffer for 30 min. The extent of ischemic injury was assessed using postischemic contractile recovery and lactate dehydrogenase (LDH) leakage into reperfusate. In the hydrogen peroxide infusion protocol, hearts were perfused with increasing concentrations of hydrogen peroxide (inflow rates 0.05-1.25 μmol/min). Inhibition of catalase activity (30.4 ± 1.8 mU/mg protein in control vs 2.4 ± 0.3 mU/mg in ATZ-treated hearts) affected neither pre-ischemic aerobic cardiac function nor post-ischemic functional recovery and LDH release in hearts subjected to 35 min cardioplegic ischemic arrest. Myocardial contents of lipid hydroperoxides were similar in control and ATZ-treated animals after 20 min aerobic perfusion, ischemia, and ischemia-reperfusion. During hydrogen peroxide perfusion, there was an increase in coronary flow rate followed by an elevation in diastolic pressure and inhibition of contractile function in comparison with control hearts. The functional parameters between control and ATZ-treated groups remained unchanged. The concentrations of myocardial lipid hydroperoxides were the same in both groups. We conclude that inhibition of myocardial catalase activity with ATZ does not predispose the rat heart to ischemia-reperfusion and hydrogen peroxide-induced injury.     

<Emphasis Type="Italic">In Vivo</Emphasis> protein transduction: Delivery of PEP-1-SOD1 fusion protein into myocardium efficiently protects against ischemic insult

Myocardial ischemia-reperfusion injury is a medical problem occurring as damage to the myocardium following blood flow restoration after a critical period of coronary occlusion. Oxygen free radicals (OFR) are implicated in reperfusion injury after myocardial ischemia. The antioxidant enzyme, Cu, Zn-superoxide dismutase (Cu, Zn-SOD, also called SOD1) is one of the major means by which cells counteract the deleterious effects of OFR after ischemia. Recently, we reported that a PEP-1-SOD1 fusion protein was efficiently delivered into cultured cells and isolated rat hearts with ischemia-reperfusion injury. In the present study, we investigated the protective effects of the PEP-1-SOD1 fusion protein after ischemic insult. Immunofluorescecnce analysis revealed that the expressed and purified PEP-1-SOD1 fusion protein injected into rat tail veins was efficiently transduced into the myocardium with its native protein structure intact. When injected into Sprague-Dawley rat tail veins, the PEP-1- SOD1 fusion protein significantly attenuated myocardial ischemia-reperfusion damage; characterized by improving cardiac function of the left ventricle, decreasing infarct size, reducing the level of malondialdehyde (MDA), decreasing the release of creatine kinase (CK) and lactate dehydrogenase (LDH), and relieving cardiomyocyte apoptosis. These results suggest that the biologically active intact forms of PEP-1-SOD1 fusion protein will provide an efficient strategy for therapeutic delivery in various diseases related to SOD1 or to OFR.     

过氧化氢加重铁对心肌的损伤作用及其机制

采用Langendorff灌流心脏和酶解分离的心肌细胞为实验模型,研究铁对心肌的损伤作用,以及过氧化氢对铁的心肌作用的影响及其可能机制.结果显示(1)羟基喹啉铁复合物(Fe-HQ)引起分离心肌细胞舒张期缩短,心肌细胞的收缩幅度和速度降低,离体灌流心脏左室发展压(LVDP)、±dp/dtmax、心率、冠脉流量呈现双相变化;冠脉流出液中乳酸脱氢酶(LDH)、肌酸激酶(CK)释放量和心肌丙二醛(MDA)增高.(2)H2O2可加重Fe-HQ对心脏的损伤,冠脉流出液中LDH、CK释放量和心肌MDA增高,而LVDP、±dp/dtmax和心率明显降低.(3)还原型谷胱甘肽可对抗Fe-HQ+H2O2对心肌的损伤作用,DMSO对Fe-HQ+H2O2致离体心脏损伤无明显作用.结果提示,心肌细胞内铁增加可引起心肌功能受损,H2O2可加重铁对心肌的损伤作用,其主要机制可能与@OH无关,而主要与含巯基的蛋白质受损有关.     

β(2)-adrenoreceptor mediates the cardioprotection of ischemic preconditioning on myocardial contraction in rats subjected to ischemia/reperfusion injury

The aim of the present study is to investigate the role of beta(2)-adrenoreceptor (beta(2)-AR) in ischemic preconditioning (IP) in isolated rat heart model of ischemia/reperfusion (I/R). Sprague-Dawley rat hearts were quickly removed, mounted on Langendorff apparatus, and perfused with Krebs-Henseleit (KH) solution. After the initial stabilization period, the rats were randomly divided into 6 groups including control group (perfused for an additional 20 min), IP group (4 cycles of 5 min of ischemia followed by 5 min of reflow), isoproterenol (ISO) group (10 nmol/L ISO perfusion for 5 min followed by 5 min washout), IP + ICI118551 group (55 nmol/L ICI118551 perfusion for 5 min before and throughout IP), ISO + ICI118551 group (55 nmol/L ICI118551 perfusion for 5 min before and throughout ISO treatment), ICI118551 group (55 nmol/L ICI118551 perfusion for 20 min). After these treatments, all hearts were followed by 30 min of no-flow ischemia and 30 min of reperfusion. A computer-based electrophysiological recorder system was used to measure changes of the maximal rate of pressure increase in systole phase (+dp/dt(max)), maximal rate of pressure decrease in diastole phase (-dp/dt(max)), and difference of left ventricular pressure (DeltaLVP). Then cardiomyocytes from these hearts were isolated by 5 min of Ca(2+)-free buffer perfusion and 25 min of collagenase perfusion. The ventricles were chopped and filtered. The myocytes were resuspended in KB buffer. The contraction and the viability of cardiomyocytes were measured. Lactate dehydrogenase (LDH) concentration in coronary effluent was assayed with assay kit. The results showed that both IP and ISO significantly increased the values of +/-dp/dt(max), DeltaLVP, the contraction and viability of cardiomyocytes, shortened the time-to-peak contraction (TTP), and decreased the release of LDH in coronary effluent. ICI118551, a selective beta(2)-AR antagonist, blocked these effects. Either the time-to-50% relaxation (R(50)) or the time-to-100% relaxation (R(100)) had no significant differences between groups. Our results indicate that the cardioprotection of IP was mediated by beta(2)-AR in isolated rat hearts subjected to I/R injury.     

Hydrogen peroxide enhanced inron-induced injury in isolated heart and ventricular cardiomyocyte in rats

To explore the cardiac effects of iron with or without hydrogen peroxide, the isolated perfused rat heart and enzymatically isolated ventricular cardiomyocyte were used. It was shown that treatment with cell-permeable iron (Fe-HQ) for 10 min reduced the contractile amplitude and velocity and end diastolic cell length in the cardiomyocyte and increased the contents of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary effluent and malondialdehyde (MDA) in the myocardium. The left ventricular developed pressure (LVDP), ± dP/dtmax, and heart rate and coronary flow are showed a biphasic phase, an increase at first followed by a decline. Treatment with hydrogen peroxide for 10 min following Fe-HQ augmented the effect of iron with an increase in coronary LDH and CK release and myocardial MDA content, and decrease in LVDP, ± dP/dtmax and heart rate. Perfusion of reduced glutathione with hydrogen peroxide counteracted these effects of Fe-HQ and hydrogen peroxide while dimethyl sulfoxide had no effect on the injury induced by Fe-HQ and hydrogen peroxide in the isolated rat heart. This suggests that augmentation of myocardial injury as a result of an increase in intracellular iron by hydrogen peroxide might involve the dysfunction of sulfydryl group containing proteins but not the hydroxyl radicals.