Protective effects of FK409, a novel nitric oxide donor, against postischemic myocardial dysfunction in guinea-pig hearts

Effects of FK409 were investigated in perfused guinea-pig Langendorff hearts subjected to ischemia and reperfusion. Nitric oxide electrode, fluorometry, and 31P nuclear magnetic resonance imaging were used to monitor changes in cellular high-phosphorous energy and nitric oxide and Ca2+ content in the heart together with simultaneous recordings of left ventricular developed pressure. After cardioplegic arrest with St. Thomas' Hospital solution, normothermic (37 degrees C) global ischemia was induced for 40 min, and hearts were reperfused for 40 min. FK409 at 10(-8) M, which has a minimum inotropic effect on nonischemic hearts, was added to the cardioplegic solution. Treatment with FK409 reduced left ventricular developed pressure during and after ischemia and improved postischemic recovery of left ventricular developed pressure from 55.4% at 40 min of reperfusion in FK409-free hearts up to 80.4% in hearts treated with FK409 (p < 0.01). Flow rate at 1.5 min after treatment with the cardioplegic solution was 27.7 ml/min in hearts treated with FK409 compared with 21.2 ml/min in drug-free hearts (p < 0.01). Treatment with FK409 significantly effected preservation of tissue level of beta-adenosine triphosphate at the end of ischemia or reperfusion. During ischemia, arrested with the cardioplegic solution, intracellular Ca2+ accumulation and nitric oxide release were reduced. At the end of ischemia in FK409-treated hearts, nitric oxide release was 86% greater than in drug-free hearts without reference to the Ca2+ concentration. In cardiac surgery, normothermic arrested hearts are subject to damage by oxygen free radicals in reperfusion injury. Therefore, nitric oxide exogenously supplied by FK409 was responsible for the cardioprotective action, presumably by acting directly as an oxygen radical scavenger during reperfusion. A specific nitric oxide donor, like FK409, may have therapeutic use as a nitric oxide-mediated vasorelaxant and additional protective action for reperfusion-injury hearts.     

Effect of ATP and verapamil as cardioplegic additives in the isolated guinea pig heart.

1. A comparative study on isolated guinea pig hearts was carried out to determine the effects of ATP and verapamil as cardioplegic additives. 2. The hearts were arrested by one of the plegic solutions: I, potassium 20 mmol/l; II, potassium 20 mmol/l+verapamil 1.1 mumol/l; III, potassium 20 mmol/l+ATP 10 mmol/l. After 45 min of hypothermic ischemia, the hearts were reperfused by Krebs-Henseleit buffer. 3. Postischemic percentage change of myocardial functions (heart rate, contractility, heart work) and tissue enzymes (LDH, SGOT, SGPT) were compared between the groups. 4. Although a rapid cardiac arrest could be obtained by verapamil added cardioplegia. Postischemic myocardial recovery was much better with ATP added cardioplegic solutions.     

Effect of ursodeoxycholic acid on ischemia/reperfusion injury in isolated rat heart

In this study, the effects of ursodeoxycholic acid (UDCA) on ischemia/reperfusion injury were investigated on isolated heart perfusion model. Hearts were perfused with oxygenated Krebs-Henseleit solution (pH 7.4, 37 degrees C) on a Langendorff apparatus. After equilibration, isolated hearts were treated with UDCA 20 to 160 microM or vehicle (0.04% DMSO) for 10 min before the onset of ischemia. After global ischemia (30 min), ischemic hearts were reperfused and allowed to recover for 30 min. The physiological (i.e. heart rate, left ventricular developed pressure, coronary flow, double product and time to contracture formation) and biochemical (lactate dehydrogenase; LDH) parameters were evaluated. In vehicle-treated group, time to contracture formation was 21.4 min during ischemia, LVDP was 18.5 mmHg at the endpoint of reperfusion and LDH activity in total reperfusion effluent was 54.0 U/L. Cardioprotective effects of UDCA against ischemia/reperfusion consisted of a reduced TTC (EC25=97.3 microM), reduced LDH release and enhanced recovery of cardiac contractile function during reperfusion. Especially, the treatments of UDCA 80 and 160 microM significantly increased LVDP and reduced LDH release. Our findings suggest that UDCA ameliorates ischemia/reperfusion-induced myocardial damage.     

Caffeic acid phenethyl ester (CAPE) supplemented St. Thomas' hospital cardioplegic solution improves the antioxidant defense system of rat myocardium during ischemia-reperfusion injury.

BACKGROUND AND AIM OF STUDY: Cardioplegic arrest remains the method of choice for myocardial protection in cardiac surgery. Caffeic acid phenethyl ester (CAPE) prevents lipid peroxidation induced by ischemia-reperfusion injury and has a potent antioxidant property. We investigated the advantages of CAPE supplemented cardioplegic solution (St. Thomas' Hospital cardioplegic solution No.: 2) on the antioxidant defense system of myocardium against ischemia-reperfusion injury. MATERIAL AND METHODS: Isolated rat hearts were mounted on a nonrecirculating type of Langendorff apparatus. The hearts were arrested for 60 min with cardioplegic solution given at 20-min intervals and then reperfused for 15 min. The hearts were divided into three groups. Cold saline (0.9%, 4 degrees C) in group 1, St. Thomas' Hospital solution in group 2 and CAPE added St. Thomas' Hospital solution in group 3 were used as the cardioplegic solution. Krebs-Henseleit buffer solution was used for reperfusion. The tissues were examined biochemically for oxidative stress. RESULTS: Significant differences among the three groups existed in tissue myeloperoxidase (MPO), catalase (CAT), Na+-K+ ATPase activity and in the concentrations of malonydealdehyde (MDA) and 3-nitrotyrosine (3-NT). Group 2 showed significant changes in MPO (P = 0.04), Na+-K+ ATPase enzyme activity (P = 0.02) and the levels of MDA (P = 0.004) and 3-NT (P = 0.01) in comparison with group 1. Group 3 efficiently reduced MDA levels (P = 0.004) and also led to significant decrease in levels of MPO (P = 0.006), 3-NT (P = 0.01) and Na+-K+ ATPase activity (P = 0.01) and increase in the level of CAT (P = 0.004) in comparison with group 1. Significant changes were also found in the levels of MDA (P = 0.03), MPO (P = 0.04) and CAT (P = 0.009) in comparison between groups 2 and 3. CONCLUSIONS: We demonstrated that the administration of CAPE into cardioplegic solutions improves the antioxidant defense system of rat heart during the ischemia-reperfusion injury.     

紫草酸镁B抑制缺血/再灌注心肌细胞c-Jun N-末端激酶3 mRNA的表达

目的探讨c-Jun N-末端激酶3(c-Jun N-terminal kinase 3, JNK3)在缺血／再灌注心肌细胞损伤中的作用,及紫草酸镁B对缺血／再灌注心脏具有保护作用的机制。方法复制大鼠Langendorff心肌缺血/再灌注损伤模型, 用原位杂交技术检测心肌细胞JNK3 mRNA的表达，并观察紫草酸镁B对JNK3表达的影响。结果图像分析显示，心肌缺血30 min/再灌注30 min时，JNK3表达明显高于非灌注组和对照组。0.1,1和10 μmol·L^-1紫草酸镁B可以抑制缺血／再灌注时JNK3 mRNA的表达。结论紫草酸镁B可通过抑制JNK3的表达以降低JNK的功能，从而减少心肌细胞凋亡的发生，对缺血／再灌注心脏产生保护作用。     

蛋白激酶C Eplison亚型在蒺藜皂苷诱导心脏保护中的作用

目的研究蒺藜皂苷对缺血/再灌注(I/R)心肌组织中蛋白激酶C Eplison亚型(PKCε)磷酸化含量及其转位的影响。方法采用Langendorff离体心脏灌流模型,40只♂SD大鼠随机等分为5组:对照组用改良Kreb-Henseleit液(K-H液持续灌注170min);I/R组(用K-H液灌流稳定20min后,停灌30min,再灌注120min);Chelerythrine组(K-H液中PKCε抑制剂1μmol.L-1);蒺藜皂苷组(K-H液中含蒺藜皂苷100mg.L-1),蒺藜皂苷+Chelerythrine组(K-H液中含蒺藜皂苷100mg.L-1+Chelerythrine1μmol.L-1),后3组I/R过程同I/R组。动态检测心率、平均动脉压。实验结束后计算心肌缺血面积,测定心脏再灌流出液肌酸激酶同工酶(CK-MB)含量变化,提取各组心肌组织检测PKCε磷酸化含量及转位情况。结果单独应用Chelerythrine对I/R心功能、心肌CK-MB及心肌缺血面积无影响;蒺藜皂苷可降低心率和平均动脉压,减少心肌CK-MB释放,缩小心肌缺血面积,促进心肌组织内PKCε磷酸化并使其由细胞质转位到细胞膜上。Chelerythrine与蒺藜皂苷合用可部分阻断蒺藜皂苷的上述作用。结论PKCε抑制剂可减弱蒺藜皂苷对离体大鼠I/R心肌的保护作用,蒺藜皂苷对I/R损伤的保护作用机制与PKCε磷酸化程度及转位有关。     

Oxidative stress developed during open heart surgery induces apoptosis: reduction of apoptotic cell death by ebselen, a glutathione peroxidase mimic

Apoptosis, a genetically controlled programmed cell death, has been found to play a role in ischemic reperfusion injury in several animal species including rats and rabbits. To examine whether this also is true for other animals, a surgically relevant model was established using an isolated in situ swine heart. Hearts were subjected to 15 min of normothermic regional ischemia by left anterior descending artery (LAD) occlusion followed by 30 min of normothermic cardioplegic arrest and 3 h of reperfusion. Oxygen free radicals have been shown to be the inducers of apoptosis and because reperfusion of ischemic myocardium is associated with the generation of free radicals, an additional group of hearts was preperfused with three different doses (5, 10, and 25 nM) ebselen, a glutathione peroxidase mimic, for 15 min before 15 min of LAD occlusion. Hearts were then subjected to 30 min of normothermic cardioplegic arrest followed by 3 h of reperfusion at normothermia. Control experiments were performed by perfusing the hearts for 4 h at normothermia. Two other groups of hearts were subjected to either 30 or 60 min of LAD occlusion followed by 30 min of cardioplegic arrest without subjecting them to reperfusion. At the end of each experiment, hearts were processed for the evaluation of apoptosis and DNA laddering. The in situ end-labeling (ISEL) technique was used to detect apoptotic cardiomyocyte nuclei while DNA laddering was evaluated by subjecting the DNA obtained from the cardiomyocytes to 1.8% agarose gel electrophoresis followed by photographing under UV illumination. The apoptotic cells appeared only after 90 min of reperfusion, as demonstrated by the intense fluorescence of the immunostained genomic DNA when observed under fluorescence microscopy. None of the ischemic hearts showed any evidence of apoptosis. These results were corroborated with the findings of DNA fragmentation showing increased ladders of DNA bands in the same reperfused hearts. The presence of apoptotic cells and DNA fragmentation in the myocardium was abolished by preperfusing the hearts in the presence of 10 nM ebselen, which also moderated the oxidative stress developed in the heart. Apoptotic cells and DNA ladders were completely absent in the hearts subjected to either 30 or 60 min of LAD occlusion. The results demonstrate that reperfusion of the ischemic heart induces apoptosis, which can be reduced with ebselen by reducing the oxidative stress associated with ischemia/reperfusion.     

银杏内酯A对缺血/再灌注损伤的大鼠心功能的影响

目的探讨银杏内酯A(Ginkgolide A,GA)对离体大鼠心肌缺血/再灌注(ischemia/reperfusion,I/R)损伤的心功能的影响。方法 Langendorff灌注离体大鼠心脏,用停灌复灌的方式制备心肌缺血/再灌注损伤模型,记录左心室收缩峰压(LVSP)、左心室舒张末压(LVEDP)、收缩压和舒张压最大变化速率(±LVdp/dtmax)和心率(HR)的变化,并测定复灌后冠状动脉流出液中LDH和SOD的含量及心肌梗死面积。分离单个细胞进行GA预处理,模拟缺血/再灌注培养后检测心肌细胞存活率和单个心肌细胞的收缩幅度。结果 GA预处理以后,LVSP、-dp/dtmax和HR在复灌10 min时较缺血/再灌注组具有明显的改善(P<0.05),并增加心率,减少LDH的生成,增加SOD的活性,降低心肌梗死面积。经GA预处理的心肌细胞存活率明显提高,10μmol.L-1GA能够明显提高缺血后单个心肌细胞的收缩幅度。结论 GA对缺血/再灌注损伤的心肌具有一定的改善作用。     

降钙素基因相关肽介导硝酸甘油增强心停搏液的保护作用(英文)

目的:研究硝酸甘油增强心停搏液的保护作用与促进降钙素基因相关肽释放的关系。方法:在StThomas Hospital心停搏液条件下,离体心脏低温缺血4h后再灌40min,记录心率、冠脉流量及心功能,并测定灌注液中降钙素基因相关肽(CGRP)的浓度及肌酸激酶(CK)的释放量。结果:硝酸甘油(0.1或1μmol/L)改善心功能,降低CK释放,同时促进CGRP的释放。CGRP(5或10nmol/L)也改善心功能及降低CK释放。预先用辣椒素耗竭感觉神经递质后。硝酸甘油的心肌保护和升高灌注液中CGRP浓度作用消失。选择性CGRP受体拮抗剂CGRP_(8-37)也能取消硝酸甘油的心肌保护作用。格列苯脲对硝酸甘油和CGRP的心保护作用均无影响。结论:硝酸甘油增强心停搏液的保护作用是通过内源性CGRP所介导,其保护作用与ATP敏感的钾通道无关。     

心律平对缺血再灌注心脏保护作用的实验研究

目的 探讨心律平（抗心律失常药）对缺血再灌注心肌的保护效果.方法 大鼠24只,离体心脏灌注,随机分为试验组与对照组：2组均应用停跳液,心脏停跳后,停灌注120 min,再灌注30 min,实验组在停跳液中加入心律平.分别测定再灌注5,10,30 min时,左心室收缩功能（LVDPi）及冠脉流量（Vi）,检测冠脉流出液中CPK-MB、LDH、TnT量;再灌注30 min,取左心室前壁内膜,检查心肌超微结构变化.结果 再灌注5,10,30 min实验组左心肌收缩功能恢复均好于对照组;漏出液中CPK-MB、LDH、TnT含量均少于对照组组.实验组超微结构损害较对照组轻.结论 停跳液中加用心律平,可减少缺血再灌注损伤,有显著的心肌保护作用.     

The cardioprotection of rutaecarpine is mediated by endogenous calcitonin related-gene peptide through activation of vanilloid receptors in guinea-pig hearts

Previous investigations have shown that calcitonin gene-related peptide (CGRP) protects against myocardial ischemia-reperfusion injury and that rutaecarpine activates vanilloid receptors to evoke CGRP release. In the present study, we examined whether rutaecarpine enhances preservation with cardioplegia in guinea-pig hearts, and whether the protective effects of rutaecarpine are related to stimulation of endogenous CGRP release via activating vanilloid receptors. The isolated guinea-pig heart was arrested using St. Thomas Hospital solution, and then reperfused with normothermic Krebs-Henseleit solution for 30 min after a 4-h hypothermic ischemic period. Hypothermic ischemia caused a decline in cardiac function (left ventricular pressure, +/-dp/dt(max), heart rate and coronary flow) and an increased release of creatine kinase during reperfusion. Rutaecarpine at the concentration of 1.0 microM significantly improved the recovery of cardiac function and reduced the release of creatine kinase during reperfusion after hypothermic ischemia. Rutaecarpine at the concentration of 3.0 microM significantly reduced the release of creatine kinase and increased the coronary flow, but only caused a slight improvement of left ventricular pressure, +/-dp/dt(max), heart rate during reperfusion. The cardioprotective effects of rutaecarpine were abolished by capsazepine, a competitive vanilloid receptor antagonist, or by CGRP (8-37), a selective CGRP receptor antagonist. Rutaecarpine at the concentration of 1.0 or 3.0 microM significantly increased the release of CGRP, which was also abolished by capsazepine. These results suggest that rutaecarpine enhances preservation with cardioplegia in guinea-pig hearts and that the protective effects of rutaecarpine are due to stimulation of endogenous CGRP release via activating vanilloid receptors.     

含血停搏液对未成熟心肌缺血-再灌注损伤的实验研究

目的观察冷血浆停搏液对未成熟心肌缺血-再灌注损伤的保护作用。方法选择14～26日龄日本大耳白兔20只,建立Langendorff离体心脏灌注模型。随机抽取4只作为正常对照组(C组),其余16只随机均分为冷血浆组(P组)和冷血组(B组)。C组灌注10minK-H液终止灌注,取右室心肌做检测用。P组、B组降温同时开始分别灌注冷血浆停搏液和冷血停搏液(4℃)15mL/kg,低温(10℃)停搏30min开始复温,再灌注37℃K-H液10min后,采集、处理和保存右室心肌标本。TUNEL法测定心肌细胞凋亡。RT-PCR检测Bcl-2mRNA,行半定量分析。结果C组心肌组织凋亡率为0,P组和B组均出现心肌细胞凋亡,P组凋亡率低于B组(P<0.05)。缺血-再灌注损伤可以使心肌组织中Bcl-2mRNA表达减弱,B组Bcl-2mRNA表达减弱更为明显,P组、B组分别与对照组比较,有显著性差异(P<0.05,P<0.01)。结论未成熟心肌缺血-再灌注伴有细胞凋亡。冷血停搏液、冷血浆停搏液对未成熟心肌缺血均具有保护作用,而冷血浆停搏液作用更为明显。     

Dose effects of adenine on myocardial ATP content in the post-anoxic nonworking rat heart

1. Tissue ATP levels were measured in Langendorff perfused nonworking rat hearts subjected to 50 min anoxia prior to reperfusion with Krebs-Ringer bicarbonate (KRB) buffer alone or supplemented with 50 microM or 1 mM adenine for 60 min. 2. ATP content was restored to the normoxic range in hearts reperfused with 50 microM adenine in KRB (20.82 +/- SEM 1.90 mumol/g dry weight vs 24.95 +/- 0.83 in normoxic hearts, P = NS). 3. Reperfusion with oxygenated KRB alone or buffer with 1 mM adenine failed to improve ATP levels (17.23 +/- 0.91 mumol/g dry weight for buffer alone, 15.60 +/- 0.46 with 1 mM adenine and 13.45 +/- 0.93 for anoxic hearts not reperfused). 4. These findings indicate that adenine at 50 microM dosage can restore ATP concentrations to the normoxic range after 60 in of anoxia in the nonworking rat heart while raising the adenine dose to 1 mM inhibited the tissue ATP content.     

Effect of long-term application of Crataegus oxyacantha on ischemia and reperfusion induced arrhythmias in rats

The effect of long-term application of Crataegus oxyacantha on ischemia and reperfusion induced arrhythmias was investigated in Wistar rats on the heart in situ and on Langendorff preparations. Seventeen rats were fed for 8 weeks with 0.5 g/kg b.w. Crataegus extract per day, standardised to 2.2% flavonoids. Twenty age-matched untreated rats served as controls. In the hearts in situ as well as in the Langendorff preparations the left anterior descending coronary artery (LAD) was ligated for 20 min and subsequently reperfused for 30 min. ECG was continuously recorded and the time spent between start of ischemia and onset of arrhythmias was measured. In addition, during ischemia and reperfusion the number of ventricular premature beats and bigemini and the duration of salvos and ventricular flutter and fibrillation were determined. The ischemic area was evaluated in all experiments and coronary flow was measured in Langendorff preparations. In the present experiments, no cardioprotective effects of Crataegus oxyacantha could be detected, neither in the heart in situ nor in the Langendorff preparations. Although the ischemic areas were identical, arrhythmias occurred even earlier in the Crataegus collectives than in the controls. Also the number and duration of ischemia and reperfusion induced arrhythmias tended to occur longer and more frequently in the Crataegus collectives, whilst coronary flow remained unchanged. The phenomenon that Crataegus rather aggravates than prevents arrhythmias may be reduced to a Crataegus induced increase in intracellular Ca(2+)-concentration proven true for the positive inotropic effects of Crataegus.     

JAK-STAT信号通路在离体大鼠心肌缺血再灌注损伤激活时程的研究

目的观察JAK-STAT信号通路在离体大鼠心肌缺血再灌注损伤过程中激活的时程及意义。方法采用Langendorff离体灌流模型,将42只雄性Wistar大鼠随机分为7组:对照组:用改良的KH液持续灌流180 min;I/R组:按再灌注时间分为R0、R5、R15、R30、R60、R120 6组,用改良的KH液灌流平衡30 min后,全心停灌30 min,分别再灌注0、5、15、30、601、20 min。连续监测左室发展压(LVDP)、左室压力最大升降速度(+dp/dtmax)以评价心功能,采用改良的Gonori变色酸(GCA)亮绿特殊染色法观察心肌缺血程度;免疫印迹法检测再灌注不同时程磷酸化的STAT1、STAT3蛋白表达的变化。结果与对照组相比,再灌注不同时程LVDP及+dp/dtmax明显降低((P<0.01),GCA特殊染色显示缺血变性的心肌细胞数量明显增多(P<0.01),再灌注各时程STAT1、STAT3均处于激活状态,与对照组相比差异有统计学意义(P<0.01)。但二者表达存在时间差异,p-STAT1在缺血30 min增高不明显,再灌注过程中处于显著激活状态(P<0.01);p-STAT3在缺血30 min即明显升高(P<0.01),而再灌注期未见进一步升高(P>0.05),p-STAT1/p-STAT3与LVDP及GCA特殊染色阳性率呈显著的相关性。结论JAK-STAT信号通路参与了心肌缺血再灌注损伤的发生,磷酸化的STAT1与STAT3的比例可能决定了再灌注损伤的严重程度。     

Cardioprotective effect of a novel cyclohexane dicarboximide derivative,ST‐6, against ischemia/reperfusion injury

Blockade of sodium overload during ischemia and reperfusion plays an important role in cardioprotection. The present study was undertaken to determine whether or not a novel cyclohexane dicarboximide derivative, ST‐6, which reveals sodium channel blockade, may protect the heart from ischemia/reperfusion injury. Isolated rat hearts were subjected to 30 min of ischemia followed by a 60‐min reperfusion. Treatment with 10 and 30 μM ST‐6 enhanced the postischemic recovery of left ventricular developed pressure, attenuated the rise in left ventricular end‐diastolic pressure, and restored high‐energy phosphate levels of the ischemic/reperfused heart. This improvement was associated with reduction of the release of creatine kinase and purine nucleosides and bases from the reperfused heart. Tissue sodium content of the ischemic as well as reperfused hearts was increased. This increase was partially reversed by treatment with ST‐6. ST‐6 had the ability to reduce V_max of the action potential of the left ventricular muscle. These results suggest that this agent is capable of reducing ischemia/reperfusion injury of the heart, probably due to attenuation in sodium overload during ischemia and reperfusion. Drug Dev. Res. 51:20–28, 2000. © 2000 Wiley‐Liss, Inc.     

The effects of ginseng total saponin,panaxadiol and panaxatriol on ischemia/reperfusion injury in isolated rat heart

The aim of the present study was to evaluate the protective effect of ginseng total saponin, panaxadiol and panaxatriol, which are the major components of Panax ginseng, against myocardial ischemia/reperfusion (I/R) injury in isolated rat hearts. Rats were orally administered once a day with total saponin (20 mg/kg), panaxadiol (5 mg/kg) and panaxatriol (5 mg/kg) for consecutive 7 days. On day 8, the hearts were isolated and perfused with Krebs-Henseleit bicarbonate buffer solution using Langendorff apparatus. After 30 min of global ischemia, hearts were reperfused for 30 min. Myocardial function, coronary flow and biochemical parameters, such as lactate dehydrogenase (LDH), creatine kinase (CK), adenosine triphosphate (ATP), malondialdehyde (MDA) and reduced glutathione (GSH) were measured. Total saponin and panaxatriol significantly improved I/R-induced myocardial dysfunction by increasing left ventricular development pressure, (−dP/dt)/(+dP/dt) and time to contracture. Moreover, the increases in the levels of LDH, CK and MDA and the decrease in the levels of GSH were attenuated by total saponin and panaxatriol. However, the ATP levels did not affected by total saponin, panaxadiol and panaxatriol pretreatment. Our findings suggest that pretreatment with ginseng total saponin, especially panaxatriol, ameliorates I/R-induced myocardial damage and this protection is caused by reducing oxidative stress.     

Protection of the reperfused ischemic isolated rat heart by phosphatidylcholine.

We examined phosphatidylcholine (PC) effects on the isolated rat heart subjected to low- or zero-flow ischemia followed by reperfusion. Untreated hearts subjected to 30 min of low-flow ischemia recovered 15% contractility following reperfusion compared to time-control hearts. Phosphatidylcholine (0.005%) addition either 10 or 20 min before ischemia significantly enhanced recovery to approximately 61% and reduced the incidence of arrhythmias during ischemia and reperfusion. Contracture during ischemia and reperfusion was significantly reduced when PC was added 20 min before ischemia. Phosphatidylcholine was ineffective when administered at the time of reperfusion except for a moderate reduction in arrhythmia development. Phosphatidylcholine also produced a salutary effect when added 20 min prior to zero-flow ischemia. Subsarcolemmal mitochondria (SLM) and, to a much lesser degree, interfibrillar mitochondria (IFM) of untreated hearts subjected to low-flow ischemia and reperfusion exhibited depressed oxidative phosphorylation which was prevented by PC. Both mitochondrial populations exhibited a marked depression in ADP/ATP translocase activity; however, this was generally unaffected by PC. Subsarcolemmal mitochondria but not IFM of zero-flow ischemic reperfused hearts also exhibited significantly depressed oxidative phosphorylation, which was unaffected by PC. Zero-flow ischemia produced a rapid and total cessation of contractility. Both populations exhibited a substantial PC-insensitive reduction in translocase activity. Our results demonstrate, for the first time, a protection by PC on the reperfused ischemic heart. The PC-induced protection following low-flow but not zero-flow ischemia is associated with improved SLM oxidative phosphorylation suggesting dissimilar contribution of mitochondria to reperfusion-associated myocardial injury.     

Inhibition of stress-activated protein kinase in the ischemic/reperfused heart: role of magnesium tanshinoate B in preventing apoptosis.

The activation of stress-activated protein (SAP) kinase may lead to an induction of apoptosis that is responsible for part of the cardiomyocyte death in reperfusion injury. The objective of the present study was to investigate the mechanism by which magnesium tanshinoate B (MTB), a bioactive compound isolated from Danshen, prevents apoptosis in cardiomyocytes in the ischemic/reperfused heart. Isolated adult rat hearts were perfused by the Langendorff mode with medium containing MTB prior to the induction of normothermic global ischemia. At the end of the 30-min ischemic period, the heart was reperfused with the same medium with or without MTB for an additional 20 min. In the MTB-treated ischemic/reperfused heart, the number of apoptotic nuclei was reduced by 2.5-fold in comparison to that in untreated ischemic/reperfused controls [23 +/- 4 vs 57 +/- 7 (mean +/- SD) TUNEL-positive cells, respectively, N = 3-4, P < 0.001]. SAP kinase activity was elevated 1.7-fold in ischemic/reperfused rat hearts [35.6 +/- 3.8 vs 21.2 +/- 3.3 (control) (mean +/- SEM) relative densitometric units, N = 4-6, P < 0.05]. Treatment with MTB abolished this elevation in SAP kinase activity (25.0 +/- 5.2 relative densitometric units), which was also decreased by 40% in the nucleus. When the heart was subjected to ischemia alone, there was no significant change in SAP kinase activity in the presence or absence of MTB. MTB did not appear to affect the p38 mitogen-activated protein kinase activity in this model system. In conclusion, MTB was shown to have cardioprotective activity against apoptosis, probably through the inhibition of SAP kinase activity.