不同处理方法心肌保护作用的比较研究

目的研究常规预适应、后处理与药物后处理对大鼠离体心脏再灌注损伤保护作用的异同并探讨其机制。方法 SD大鼠共50只,随机分为5组:停灌/再灌组(I/R);预适应组(IPC);后处理组(POS);吗啡后处理组(MOR);预适应加后处理组(IPC+POS),行Langendorff心脏灌流。观测其血流动力学、心肌梗死面积、肌酸激酶(CK)、乳酸脱氢酶(LDH)以及超微结构变化。结果与I/R相比,4个实验组均能明显的改善心功能,减小心梗面积,减少心肌酶释放,减轻超微结构损伤。而MOR的心肌保护作用明显低于IPC、POS和IPC+POS。此三组的心肌保护效果差异有统计学意义(P<0.05)。结论预适应和后处理可能有大部分相同的心肌保护机制。而药物后处理只能激活部分机制而达到部分心肌保护作用。     

卡托普利介导缓激肽诱导预适应对大鼠缺血再灌注心肌的保护作用

目的:探讨卡托普利介导缓激肽诱导预适应对大鼠缺血再灌注心肌保护作用的机制.方法:将60只Wistar大鼠随机分成正常对照组、缺血再灌注(IR)组、卡托普利预处理组、缓激肽β2受体拮抗剂B 1650加卡托普利组.麻醉大鼠冠脉结扎30min后,再灌注60min,观察各组缺血再灌注前后心功能及一氧化氮合酶(NOS)、谷胱甘肽过氧化物酶(GSH-PX)、超氧化物歧化酶(SOD)活性以及丙二醛(MDA)和一氧化氮(NO)含量的变化.结果:IR组心肌原生型NOS(cNOS)活性及总NOS活性显著下降(P均＜0.01),NO产生减少(P＜0.05～0.01);卡托普利组缺血再灌注期间NO水平高于IR组(P＜0.01),再灌注30 min心肌cNOS活性(P＜0.01)及总NOS活性(P＜0.05)显著高于IR组,心肌损害较IR组减轻.先静注B1650后再给予卡托普利,则卡托普利对心肌损伤的保护作用明显减弱.结论:NO产生不足是心肌再灌注损伤的主要因素;卡托普利通过调节缓激肽活性,维持正常NO水平对缺血再灌注心肌损伤大鼠可产生药理预适应保护作用,该作用可由缓激肽所介导.     

针刺手厥阴心包经穴对缺血/再灌注大鼠心肌离子泵的影响

目的:观察针刺心包经穴对大鼠心肌缺血/再灌注损伤过程中心肌细胞Na -K -ATP酶和Ca2 -Mg2 -ATP酶活性的影响,探讨其心肌保护作用的机制.方法:50只大鼠随机分为5组.假手术组只穿线不结扎冠状动脉,其余各组制备缺血/再灌注动物模型,其中3个针刺穴位组分别于电针大鼠内关穴、郄门穴或支沟穴20 min后,结扎冠状动脉左前降支40 min,心电图监测,再电针相应穴位20 min,恢复灌流.假手术组于穿线后100 min、模型组和各针刺穴位组于再灌注60 min摘取心脏,取心室肌制备心肌细胞膜,定磷法观察Na -K -ATP酶和 Ca2 -Mg2 -ATP酶活性的变化.结果:针刺心包经穴(内关、郄门)组Na -K -ATP酶和 Ca2 -Mg2 -ATP酶活性均明显升高,与模型组比较差异均非常显著(P均<0.01).结论:针刺手厥阴心包经穴可提高Na -K -ATP酶和Ca2 -Mg2 -ATP酶活性,减轻心肌细胞钙超载程度,有效地保护心肌.     

大鼠心肌缺血再灌注损伤与红花黄素的保护作用

目的:观察大鼠心肌缺血再灌注损伤模型心肌组织中超氧化物歧化酶、谷胱甘肽过氧化物酶、诱导型一氧化氮合酶、总一氧化氮合酶活性及一氧化氮,丙二醛含量的变化,探讨红花黄素对离体大鼠缺血再灌注心肌的保护作用。方法:①实验于2004-06/2005-02在南阳医学高等专科学校药理学教研室完成。选用健康Wistar大鼠32只,随机分为4组,每组8只:正常对照组、模型组、红花黄素组、地奥心血康组。②采用Langendorff创建的离体心脏灌流法建立离体大鼠心肌缺血缺氧再灌注损伤模型。以持续平衡的充有体积分数0.95O2+0.05CO2混合气体的KH液进行非循环逆行灌流。灌注数秒后心脏恢复跳动。稳定15min后停灌30min,再灌40min,给药组在停灌前10min以红花黄素(0.33g生药/mL)或地奥心血康灌注,直至再灌后40min。正常对照组离体心脏持续灌注K-H液90min。模型组离体心脏灌注K-H液35min,全心缺血25min,再灌注30min。③心肌中超氧化物歧化酶、谷胱甘肽过氧化物酶、一氧化氮合酶活性变化、一氧化氮、丙二醛含量测定按南京建成生物工程研究所提供的相应试剂盒说明完成。④分别进行成组t检验和配对t检验。结果:进入结果分析大鼠32只。①超氧化物歧化酶、谷胱甘肽过氧化物酶活力:模型组明显低于其他3组(P<0.05～0.01);丙二醛含量:模型组明显高于其他3组(P<0.05～0.01)。②一氧化氮含量:模型组明显低于其他3组(P<0.05～0.01)。③诱导型一氧化氮合酶活力:地奥心血康组明显高于模型组(P<0.01);总一氧化氮合酶活力:模型组明显高于对照组和红花黄素组(P<0.01),明显低于地奥心血康组(P<0.05)。结论:红花黄素对离体大鼠缺血再灌损伤的心肌具有保护作用,此作用可能与抑制心肌脂质过氧化、增强抗氧化能力有关。     

口服绿茶多酚对离体心脏的保护作用

目的:探讨口服绿茶多酚对离体心脏的保护作用。方法:16只SD大鼠,随机分为两组,实验组每天经胃管灌服5%绿茶多酚溶液40mL,对照组灌服生理盐水,20d后分别摘取心脏行离体灌注(Langendorff模型),测定心功能,然后灌注并保存于4℃UW保存液中,8h后取出,再行Langendorff灌注,再次测定心功能参数。测定再灌注后冠脉流出液中的乳酸脱氢酶(LDH)、肌酸激酶(CK)活性,心肌组织中超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量;观察心肌超微结构。结果:除心率外,实验组各项心功能参数均优于对照组(P<0.05),心肌含水量、MDA低于对照组(P<0.05),冠脉流出量、心肌组织中SOD活性优于对照组(P<0.05),冠脉流出液中LDH、CK活性低于对照组(P<0.05);实验组心肌超微结构的损伤较对照组显著减轻。结论:口服绿茶多酚对大鼠离体心脏具有保护作用。     

不同预适应方法抗缺血/再灌注心律失常的实验研究

观察不同预适应方法对缺血 /再灌性心律失常的保护作用。方法　采用大鼠离体心脏Langendorff灌流模型 ,用冠脉结扎和松脱来复制心肌缺血再灌注损伤。结果　按Curtis -Walker心律失常评分系统计算 ,缺血再灌注损伤组为3 43± 0 48,药物、结扎和旷置预适应保护组分别降至 1 0 0± 0 45、0 6 7± 0 2 1、0 71± 0 2 9(P <0 0 1)。旷置预适应可使再灌注时的冠脉流出液的乳酸脱氢酶释放量明显减少 (P <0 0 5 ) ,心室纤颤阈显著提高 (P <0 0 5 )。结论　不同预适应方法均具有明显的心肌保护作用     

大鼠心肌缺血再灌注损伤与红花黄素的保护作用

目的：观察大鼠心肌缺血再灌注损伤模型心肌组织中超氧化物歧化酶、谷胱甘肽过氧化物酶、诱导型一氧化氮合酶、总一氧化氮合酶活性及一氧化氮，丙二醛含量的变化，探讨红花黄素对离体大鼠缺血再灌注心肌的保护作用。 方法：①实验于2004—06／2005—02在南阳医学高等专科学校药理学教研室完成。选用健康Wistar大鼠32只，随机分为4组，每组8只：正常对照组、模型组、红花黄素组、地奥心血康组。②采用Langendofff创建的离体心脏灌流法建立离体大鼠心肌缺血缺氧再灌注损伤模型。以持续平衡的充有体积分数0．95O2＋0．05CO2混合气体的KH液进行非循环逆行灌流。灌注数秒后心脏恢复跳动。稳定15min后停灌30min，再灌40min，给药组在停灌前10min以红花黄素（0．33g生药／mL）或地奥心血康灌注，直至再灌后40min。正常对照组离体心脏持续灌注K—H液90min。模型组离体心脏灌注．K—H液35min，全心缺血25min，再灌注30min。③心肌中超氧化物歧化酶、谷胱甘肽过氧化物酶、一氧化氮合酶活性变化、一氧化氮、丙二醛含量测定按南京建成生物工程研究所提供的相应试剂盒说明完成。④分别进行成组t检验和配对t检验。 结果：进入结果分析大鼠32只。①超氧化物歧化酶、谷胱甘肽过氧化物酶活力：模型组明显低于其他3组（P〈0．05～0.01）；丙二醛含量：模型组明显高于其他3组（P〈0．05～0．01）。②一氧化氮含量：模型组明显低于其他3组（P〈0．05～0．01）。③诱导型一氧化氮合酶活力：地奥心血康组明显高于模型组（P〈0．01）；总一氧化氮合酶活力：模型组明显高于对照组和红花黄素组（P〈0．01），明显低于地奥心血康组（P〈0．05）。 结论：红花黄素对离体大鼠缺血再灌损伤的心肌具有保护作用，此作用可能与抑制心肌脂质过氧化、增强抗氧化能力有关。     

异丙酚激活蛋白激酶C对心肌缺血再灌注损伤的保护作用

目的:观察异丙酚对大鼠离体心肌缺血再灌注的影响及蛋白激酶C激活的作用。方法:实验于2004-04/2005-03在河北省医学科学院药研室完成。48只大鼠离体心脏随机分为6组,每组8只。分别为:正常对照组,持续灌注Lock液65min;缺血再灌注模型组,用含脂肪乳对照的灌流液灌注15min后,以钳夹主动脉灌注管造成全心常温缺血25min后,恢复再灌注30min,灌流液与预灌时相同;异丙酚15,30,60μmol/L组,缺血前和再灌期的灌流液中分别含相应浓度的异丙酚,余同缺血再灌注模型组;异丙酚60μmol/L 蛋白激酶抑制剂5μmol/L组,灌流液中含5μmol/L的chelerythrine的灌流液,其余同异丙酚60μmol/L组。实验评估:①Powerlab/8s仪记录各组平衡末、缺血前及再灌30min时心率、左室发展压、左室舒张末压、左室压力变化速率、冠状动脉流量等心功能指标。②测定冠状动脉流出液中乳酸脱氢酶、磷酸肌酸激酶活性。③透射电镜观察心肌细胞超微结构变化。④差速离心提取心肌线粒体,测定线粒体超氧化物岐化酶、谷胱甘肽过氧化物酶、ATP酶活性和丙二醛含量。结果:48只大鼠均进入结果分析。①平衡灌注末、缺血前各组间心功能指标差异无显著性(P>0.05),再灌注30min末,异丙酚30,60μmol/L组左室发展压、左室压力变化速率、冠状动脉流量明显高于缺血再灌注模型组(P<0.05),左室舒张末压明显低于缺血再灌注模型组(P<0.05)。异丙酚60μmol/L 蛋白激酶C抑制剂5μmol/L组左室发展压、左室压力变化速率、冠状动脉流量明显低于单纯异丙酚60μmol/L组(P<0.05),但仍高于与缺血再灌注模型组(P<0.05)。②心肌缺血再灌后,冠状动脉流出液中乳酸脱氢酶和肌酸激酶活性明显高于正常对照组(P<0.05)。异丙酚30,60μmol/L组、异丙酚60μmol/L 蛋白激酶C抑制剂5μmol/L组乳酸脱氢酶、肌酸激酶活性明显低于缺血再灌注模型组(P<0.05),异丙酚60μmol/L 蛋白激酶C抑制剂5μmol/L组乳酸脱氢酶和肌酸激酶活性与异丙酚60μmol/L组无明显差异。③与缺血再灌注模型组相比,异丙酚组心肌损伤明显减轻,尤其是60μmol/L组,心肌纤维排列均匀,线粒体膜结构完整,仅轻度水肿,嵴清晰,糖原可见。异丙酚60μmol/L 蛋白激酶C抑制剂5μmol/L组心肌超微结构显示损伤程度重于异丙酚60μmol/L组。④异丙酚30,60μmol/L、异丙酚60μmol/L 蛋白激酶C抑制剂5μmol/L组丙二醛含量低于缺血再灌注模型组(P<0.05),ATP酶、超氧化物歧化酶、谷胱甘肽过氧化物酶活性明显高于缺血再灌注模型组(P<0.05)。异丙酚60μmol/L组与异丙酚60μmol/L 蛋白激酶C抑制剂5μmol/L组相比,上述指标无明显差异。结论:异丙酚对离体大鼠心肌缺血再灌注损伤有保护作用,可能与其抗脂质过氧化和激活蛋白激酶C有关。     

三种鼠尾草注射液对离体大鼠心肌缺血再灌注损伤的保护作用

目的研究云南产鼠尾草属药物滇丹参、甘西鼠尾、褐毛甘西鼠尾对心肌缺血再灌注损伤的保护作用,并与丹参进行对比.方法采用Langendorff离体心脏灌流法,全心停灌后再灌流造成心肌缺血再灌注模型,通过动脉套管侧管给药.测定再灌注30min后,灌流液中CK、LDH、SOD、GSH-Px和MDA含量;同时测定离体心脏冠脉流量、心肌收缩幅度和心率.结果滇丹参、甘西鼠尾、褐毛甘西鼠尾可以对抗离体大鼠心脏停灌后再灌注引起的冠脉流量、心肌收缩幅度和心率的降低(P<0.01,P<0.05);降低灌流液中CK、LDH和MDA含量,提高SOD和GSH-Px的活力(P<0.01,P<0.05).结论滇丹参、甘西鼠尾、褐毛甘西鼠尾对在体和离体缺血/再灌注心肌有保护作用.     

内洋地黄素介导大鼠心肌缺氧复氧损伤的实验研究

目的研究内洋地黄素在离体大鼠心脏缺氧复氧损伤中的变化,观察内洋地黄素特异性拮抗剂地高辛抗血清对大鼠心脏缺氧复氧损伤的保护作用,明确内洋地黄素在心脏缺氧复氧损伤中的作用与机制。方法制备离体大鼠心脏缺氧复氧损伤模型,SD大鼠随机分为6组(n=10):正常对照组,缺氧复氧损伤组,维拉帕米组,小剂量、中剂量、大剂量地高辛抗血清组。连续记录各组心外膜ECG、HR、LVDP、±dp/dtmax。各组于复氧灌流结束时,取左心室心肌组织测定心肌匀浆中内洋地黄素含量、MDA含量、细胞膜Na+K+ATP酶活性以及线粒体内Ca2+水平。结果缺氧复氧损伤组ECG表现为ST段显著抬高,心率减慢,LVDP和±dp/dtmax显著降低,于复氧灌流早期出现严重室性心律失常;心肌组织内洋地黄素水平和MDA含量明显升高,细胞膜Na+K+ATP酶活性明显下降,线粒体内Ca2+水平显著升高。中、大剂量地高辛抗血清能明显降低心肌组织内洋地黄素水平和MDA含量,恢复心肌细胞膜Na+K+ATP酶活性,降低线粒体内Ca2+水平,改善心肌缺血性ST段抬高,显著改善血流动力学,拮抗再灌注引起的室性心律失常。结论地高辛抗血清通过拮抗内洋地黄素,恢复心肌细胞膜Na+K+ATP酶活性,减轻细胞内Ca2+超载,对缺氧复氧损伤心肌有明显的保护作用。表明内洋地黄素是介导心肌缺氧复氧损伤的重要     

Interleukin-2 increases activity of sarcoplasmic reticulum Ca2+-ATPase,but decreases its sensitivity to calcium in rat cardiomyocytes

To further explore the role of interleukin-2 (IL-2) in cardiac function, we investigated its effects on the intracellular calcium transient and the activity of sarcoplasmic reticulum (SR) Ca2+-ATPase in rat cardiomyocytes. IL-2 (200 U/ml) decreased the amplitude of electrically stimulated and caffeine-induced intracellular Ca2+ transients in ventricular myocytes, but increased the end-diastolic calcium level. IL-2 did not affect the sarcolemmal L-type Ca2+ channel activity. The activity of SR Ca2+-ATPase from IL-2-treated hearts increased in a dose-dependent manner, but the sarcolemmal Ca2+-ATPase activity did not change. After incubation of SR with ATP, the activity of SR Ca2+-ATPase from IL-2-treated hearts increased much more than that in the control group. The responsiveness of SR Ca2+-ATPase from IL-2-perfused hearts to the free calcium concentration was inhibited. The Ca2+ uptake and Ca2+ content were reduced in the SR vesicles prepared from IL-2-treated rat heart. Pretreatment with the kappa-opioid receptor antagonist nor-binaltorphimine (10 nM) attenuated the effect of IL-2 on the SR Ca2+-ATPase activity, SR Ca2+ uptake, and Ca2+ content. The activity of Ca2+-ATPase in SR isolated from untreated hearts did not change when IL-2 and SR were coincubated. Thus, we conclude that the decreased calcium transient induced by IL-2 results from reduced SR calcium release, which is due to decreased SR Ca2+ uptake mediated by cardiac kappa-opioid receptors, but not from reduced activity of the sarcolemmal L-type calcium channel.     

地塞米松诱导金属硫蛋白表达对大鼠缺血/再灌注损伤心肌的保护作用研究

目的 探讨地塞米松诱导金属硫蛋白(MT)表达对大鼠缺血/再灌注(I/R)损伤心肌的延迟保护作用.方法 将32只SD大鼠随机分成地塞米松组和对照组,分别予腹腔注射地塞米松和蒸馏水预处理.预处理24 h后构建Langendorff离体心脏I/R动物模型,缺血30 min后再灌注60 min.用蛋白质免疫印迹法(Western blotting)检测MT表达;动态观测缺血前及再灌注期间血流动力学指标[左心室发展压(LVDP)、左室内压上升和下降最大速率(±dp/dt max)、冠状动脉循环流出量(CF)]、心律失常的变化;测定心肌梗死面积、冠状动脉流出液肌酸激酶同工酶(CK-MB)漏出率、心肌丙二醛(MDA)、总超氧化物歧化酶(T-SOD)、铜锌-SOD(CuZn-SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化酶(GSH-Px)水平及心肌细胞膜Na+-K+-ATP酶、Ca2+-Mg2+-ATP酶活性.结果 与对照组比较,地塞米松组MT的表达水平显著增加(3.085±1.065比1.028±0.016,P＜0.05);再灌注期间LVDP、±dp/dt max及CF均得到明显改善(P均＜0.05);再灌注性室性心律失常评分明显减少[(2.00±1.41)分比(6.63±4.24)分,P＜0.05];心肌梗死面积明显缩小[(28.38±11.22)%比(47.39±8.30)%,P＜0.01];冠状动脉流出液CK-MB的漏出率明显降低[(8.69±4.16)U/g比(18.15±5.59)U/g,P＜0.01];心肌组织MDA含量降低(P＜0.05),T-SOD、CuZn-SOD、CAT、GSH-Px均明显升高(P＜0.05或P＜0.01);心肌细胞膜的Na+-K+-ATP酶、Ca2+-Mg2+-ATP酶活性增加(P＜0.01和P＜0.05).结论 地塞米松可能通过上调MT的表达,对大鼠I/R损伤心肌起到延迟保护作用.     

葛根素预处理对离体大鼠心肌缺血再灌注损伤的保护作用

目的通过建立大鼠离体心脏缺血再灌注模型,探讨葛根素预处理对大鼠心肌缺血再灌注损伤的保护作用及其可能机制。方法在langendǒrff离体心脏体外灌注模型复制基础上,采用随机对照方法将50只雄性SD大鼠平均分为5组:对照组、缺血再灌注组、缺血预处理组、小剂量葛根素预处理组、大剂量葛根素预处理组,记录每只大鼠平衡灌注15 min、再灌注153、0 min的心功能变化,包括心率(HR)、左室最高压(LVSP)、左室舒张末压(LVEDP)、左室压力升高速率(+dp/dtmax)、左室压力降低速率(-dp/dtmax)。并于平衡灌注15 min、复灌1、3、5、10、15、30 min测定冠脉流出液中肌酸激酶(CK)的含量。测定心肌丙二醛(MDA)、超氧化物歧化酶(SOD)、一氧化氮(NO)的含量,并作电镜检查。结果缺血再灌注组可引起HR、LVSP、+dp/dtmax、-dp/dtmax下降,LVEDP升高以及CK释放增加,心肌MDA产生增多、SOD及NO含量降低,与对照组相比有显著性差异。缺血预处理组及葛根素预处理组均能显著改善缺血再灌注引起的心功能损伤,降低CK的释放,减少心肌组织MDA的生成,并增加心肌组织中SOD和NO含量,减轻心肌细胞超微结构的病理改变。大剂量葛根素预处理组比小剂量葛根素预处理组对上述指标的改善更为显著。结论葛根素预处理能减少脂质过氧化,明显改善心功能,提高心肌组织对后续缺血的耐受性。这种保护作用存在量效关系,其产生与心肌中SOD增高减轻了氧自由基损伤和NO增高扩张冠脉有关。     

参附注射液对缺血再灌注心肌损伤的保护作用

目的：探讨参附注射液对缺血／再灌注（I／R）损伤心肌的保护作用及其机制。方法：32只雄性SD大鼠随机分为4组：正常对照组（n=8）、缺血／再灌注组（n=8）、参附注射液30mg／L组（n=8）和100mg／L组（n=8）。采用Langendorff离体心脏灌流模型，制备心肌缺血再灌注损伤模型，在心脏缺血前和再灌注后，给予参附注射液，观察离体大鼠心脏血流动力学指标和心肌组织中的高能磷酸化舍物ATP含量、MDA含量及SOD活性等的变化。结果：参附注射液100mg／L明显改善缺血／再灌注后心脏血流动力学指标。缺血／再灌注组大鼠心肌ATP含量和SOD活性明显降低，MDA含量明显升高。与缺血／再灌注组比较，参附注射液30mg／L组和100mg／L组心肌MDA值减少（P〈O．05），SOD值升高（P〈0．05）；参附注射液100mg／L组ATP含量增加（P〈0．05）。结论：参附注射液能通过提高心肌组织ATP含量和SOD活性，减少MDA含量，改善缺血／再灌注后心脏血流动力学紊乱，减轻大鼠心肌缺血再灌注损伤。     

Myocardial protective effects of nicorandil, an opener of potassium channels on senile rat heart

The purpose of this study was to investigate the cardioprotective effects of nicorandil, an opener of potassium channels, on senile rat hearts from ischemic reperfusion injury. A modified working model of isolated perfused hearts of senile rats was used. After isolation, the hearts underwent 60 min of global hypothermic ischemia treatment, followed by 30 min of reperfusion. These hearts were distributed into three groups, each receiving different cardioplegic solutions: (1) St. Thomas' solution (Group S), (2) 100 micromol/L nicorandil (Group N), (3) St. Thomas' solution combined with 100 micromol/L nicorandil (Group S+N). The pre- and post-ischemic myocardial function were assessed by the percentage recovery of the heart rate (HR), +/- dp/dt(max) (maximal rate of change of left ventricular pressure) and cardiac output (CO). Upon reperfusion, the cardioplegic solution was collected from the coronary sinus and tested for lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) activity. During 30 min of reperfusion, the percentage recovery of HR, +dp/dt and left ventricular stroke work (LVSW) were significantly higher in Group S+N than in Group S and Group N (p < 0.05). The percentage of recovery in CO was higher in Group N and Group S+N than in Group S. The electrical activities arresting time (EAT) and mechanical activities arresting time (MAT) were longer in Group N than in Group S and Group N+S (p < 0.01). There were no statistical significance between Group S and Group N+S (p > 0.05). There were no significant differences in the levels of LDH and CK-MB. Electron microscopic examination revealed better preservation of the ultrastructures of the myocardial tissue in Group N+S than the other two groups. These results indicate that nicorandil combined with St. Thomas' solution can improve the left ventricular function of the post-ischemic senile rat and offer a better myocardial protective effect on the ischemic senile myocardium.     

ATP-loaded liposomes effectively protect mechanical functions of the myocardium from global ischemia in an isolated rat heart model.

ATP-loaded liposomes (ATP-L) infused into Langendorff-instrumented isolated rat hearts protect the mechanical functions of the myocardium during ischemia/reperfusion. The left ventricular developed pressure (LVDP) at the end of the reperfusion in the ATP-L group recovered to 72% of the baseline (preservation of the systolic function) compared to 26%, 40%, and 51% in the groups treated with Krebs-Henseleit (KH) buffer, empty liposomes (EL), and free ATP (F-ATP), respectively. The ATP-L-treated group also showed a significantly lower left ventricular end diastolic pressure (LVEDP; better preservation of the diastolic function) after ischemia/reperfusion than controls. After incubating the F-ATP and ATP-L with ATPase, the protective effect of the F-ATP was completely eliminated because of ATP degradation, while the protective effect of the ATP-L remained unchanged. Fluorescence microscopy confirmed the accumulation of liposomes in ischemic areas, and the net ATP in the ischemic heart increased with ATP-L. Our results suggest that ATP-L can effectively protect myocardium from ischemic/reperfusion damage.     

Alternative mechanisms for atriopeptin prohormone processing by isolated perfused rat hearts

The isolated perfused rat heart releases atriopeptin-28 [AP28 (ANF99-126)], whereas the storage form of AP in the heart is the intact prohormone AP126 (ANF1-126). Right atrial stretch or phenylephrine (5 x 10(-5) M) stimulated the release of AP28. The processing of the prohormone during stretch was inhibited by infusion of the protease inhibitor aprotinin, resulting in the appearance of intact AP126 in the cardiac effluent. Other protease inhibitors including p-aminobenzamidine and soybean trypsin inhibitor did not alter prohormone processing by the isolated heart subjected to stretch. In contrast, aprotinin did not block the prohormone processing induced by phenylephrine. Ca+(+)-free medium markedly inhibited prohormone processing during stretch without a significant effect on AP release, whereas phenylephrine-stimulated AP release was completely suppressed by Ca+(+)-free medium. Exogenous AP126 could be cleaved by isolated rat hearts perfused either with Krebs-Henseleit solution or with Ca+(+)-free medium. However, amino acid sequence analysis revealed that the prohormone cleavage in Ca+(+)-free medium occurred at sites other than between Arg98 and Ser99 and that the resultant low molecular weight APs were not AP28. These findings suggest: 1) the characteristics of the enzyme(s) involved in the processing of AP prohormone in isolated perfused rat hearts are different from the described properties of purified enzymes; 2) in isolated perfused rat hearts the specific AP processing enzyme is Ca++ dependent, whereas nonspecific cleavage does not necessarily require Ca++ and 3) two independent AP processing pathways differentially activated by mechanical (stretch) and pharmacologic (alpha 1-adrenergic agonist) stimuli exist.     

牛磺酸对大鼠缺血心肌缺血再损伤的保护作用

目的探讨大鼠心肌缺血损伤与凋亡蛋白 Bcl-2和 Bax的关系及牛磺酸的影响. 方法选择健康 SD大鼠 30只,随机分为假结扎组、结扎组和牛磺酸保护组,每组 10只.结扎大鼠冠状动脉左前降支建立心肌缺血模型.检测 3组心肌线粒体中超氧化物歧化酶( superoxide dismutase,SOD)、 Ca2+-ATP酶活性和丙二醛含量,用免疫组化法检测心肌中的 Bcl-2和 Bax蛋白. 结果结扎冠状动脉左前降支可致心肌线粒体丙二醛含量升高 [假结扎组 (4.89± 0.54) μ mol/g;结扎组( 9.85± 0.68) μ mol/g], SOD和 Ca2+-ATP酶活性下降 [假结扎组( 8.63± 0.35) μ mol/( g· s) ,(13.97± 1.97) mmol/( g· s) ;结扎组( 6.73± 0.39) μ mol/( g· s), (8.54± 2.28) mmol/( g· s) ].缺血心肌 Bax蛋白表达呈显著升高 (t=3.931, P< 0.01),牛磺酸能明显减少缺血心肌线粒体丙二醛的生成 [牛磺酸保护组 (5.46± 0.72) μ mol/g],降低心肌 Bax蛋白的表达,增加 Bcl-2蛋白的表达 ( t=3.716, P< 0.01). 结论结扎大鼠冠状动脉左前降支所致心肌缺血损伤与 Bcl-2和 Bax蛋白的表达有关 ,牛磺酸对缺血心肌 Bcl-2和 Bax蛋白的表达有较好的调控作用.     

The effects of ryanodine on calcium uptake by the sarcoplasmic reticulum of ischemic and reperfused rat myocardium

Summary— The effects of ischemia and reperfusion on sarcoplasmic reticulum (SR) calcium uptake were measured in crude heart homogenates of rats and were compared to published results for rabbit hearts. Isolated rat hearts ( n = 5 in each group) were Langendorff-perfused at 37 °C and were either kept normally perfused (control group), or submitted to 15 min normothermic ischemia (ischemic group), or reperfused for 10 min after 15 min ischemia (reperfused group). Mechanical function recovered to 50–60% of control after 10 min reperfusion following ischemia. Ca uptake (control V_max; 23.0 ± 2.20 nmol·min⁻¹·mg of protein⁻¹) decreased during ischemia (V_max: 15.7 ± 1.60 nmol·min⁻¹·mg⁻¹) but recovered to control level on reperfusion (V_max: 20.8 ± 2.02 nmol·min⁻¹·mg⁻¹). An increased Ca uptake was obtained when the measurements were carried out in the presence of ryanodine (430 μM) to block Ca leakage through SR Ca-release channels. The relative magnitude of ryanodine effect in the ischemic myocardium (increase: 77.2 ± 18.20%) was more marked than in control (32.0 ± 8.22%) or reperfused myocardium (39.0 ± 10.66%). This result is different from that of rabbit myocardium where similar ryanodine effect is present in all groups (56.7 ± 13.76%, 50.0 ± 13.56% and 54.2 ± 6.88% in control, ischemic and reperfused hearts, respectively) and suggests that a component of cytosolic Ca overload via SR Ca-release channels is present during ischemia in rat, but not in rabbit myocardium.     

左卡尼汀强化St.Thomas No.2液对低温离体心脏的保存效果

背景：在心脏瓣膜置换中应用添加左卡尼汀的心脏停搏液可明显减轻心肌线粒体的脂质过氧化反应,保护心肌细胞。目的：观察加入左卡尼汀的St.Thomas No.2液对大鼠离体心脏低温保存的效果。方法：利用Langendorff灌注装置建立SD大鼠离体心脏灌注和工作模型,随机分成4组,其中2组采用St.Thomas No.2液作为心脏停搏液与保存液分别保存心脏4h、6h,另2组采用添加左卡尼汀的St.Thomas No.2液作为心脏停搏液与保存液分别保存心脏4h、6h。结果与结论：与St.Thomas No.2液保存4h组比较,添加左卡尼汀的St.Thomas No.2液保存4h组心脏心率、冠状动脉流量、左心室收缩峰压和左心室内最大上升速率及心肌含水量、ATP含量差别无显著性意义（P〉0.05）,但心肌酶漏出量明显减少（P〈0.05）;添加左卡尼汀的St.Thomas No.2液保存6h组上述指标检测结果均优于St.Thomas No.2保存6h组（P〈0.05）。提示左卡尼汀强化的St.ThomasNo.2液可显著提高大鼠离体心脏的低温保存效果。