缺血后功能低下大鼠心肌钙与水含量的变化及高渗甘露醇的影响

缺血后心室功能减低(myocardial stunning)的发生机制迄今尚不明了。本实验以 Lang-cndorff 法在离体灌流的大鼠心脏,研究了全心缺血20min 及再灌注40min 后心肌 Ca~(2+)、Na~+K~+、Mg~(2+)及 H_2O 含量的变化,以及高渗甘露醇对缺血后功能低下心肌的影响。实验发现:(1)缺血/再灌注后心肌组织中 Ca~(2+),H_2O 的含量与非缺血组相比分别增加42%(P<0.01)及7.6%(P0.05)。(2)于再灌注同时给予12%高渗甘露醇可明显改善缺血后心室功能:再灌注40min 时,心率-左室压乘积恢复达缺血前的85%,而不给甘露醇仅恢复66.3%(p<0.01);高渗甘露醇同时消除了缺血后功能低下心肌中 Ca~(2+)超负荷与心肌水肿,此现象提示缺血/再灌注引起的肌膜非特异性通透性改变,很可能是钙进入细胞内的路径之一。本研究结果表明,心肌 Ca~(2+)超负荷及轻度心肌水肿参与了缺血后心室功能低下,高渗甘露醇在离体大鼠心脏可明显改善缺血后功能低下心肌的功能,此作用至少部分是由于其具有减低心肌钙与水含量的效应。     

ESR检测大鼠心脏缺血—再灌产生的氧自由基及药物的消除

据报道,心肌缺血——再灌损伤的机制与活性氧自由基的产生紧切相关,在大鼠心脏产生氧自由基是以黄嘌呤氧化酶(XO)途径为主.心肌中的黄嘌呤脱氢酶(XD)在Ca~(2+)激活水解酶的作用下向XD转化.而此我们设想,协同使用钙拮抗剂与超氧阴离子(O_2~1)清除剂(超氧化物歧化酶,SOD)可能加强对心肌的保护作用.本实验用电子自旋共振波谱仪(ESR)直接检测大鼠缺血——再灌心肌产生的活性氧自由基,从心脏收缩幅度,静息张力,肌酸激酶(CK)释放和心肌组织丙二醛(MDA)为指标,观察钙拮抗剂硫氮(艹卓)酮(DTZ)和SOD的分别作用和联合作用,发现两药合用可明显减少心肌活性氧自由基的产生.     

ESR检测大鼠心脏缺血—再灌产生的氧自由基及药物的消除

据报道,心肌缺血——再灌损伤的机制与活性氧自由基的产生紧切相关,在大鼠心脏产生氧自由基是以黄嘌呤氧化酶(XO)途径为主.心肌中的黄嘌呤脱氢酶(XD)在Ca~(2+)激活水解酶的作用下向XD转化.而此我们设想,协同使用钙拮抗剂与超氧阴离子(O_2~1)清除剂(超氧化物歧化酶,SOD)可能加强对心肌的保护作用.本实验用电子自旋共振波谱仪(ESR)直接检测大鼠缺血——再灌心肌产生的活性氧自由基,从心脏收缩幅度,静息张力,肌酸激酶(CK)释放和心肌组织丙二醛(MDA)为指标,观察钙拮抗剂硫氮(艹卓)酮(DTZ)和SOD的分别作用和联合作用,发现两药合用可明显减少心肌活性氧自由基的产生.     

人参茎叶皂甙对高胆固醇饮食大鼠再灌注性心律失常和脂质过氧化的影响(英文)

研究人参茎叶皂甙(GSL)对高胆固醇饮食大鼠心肌再灌注性心律失常(RPA_r)和脂质过氧化的影响。方法:将胆固醇乳剂用灌胃法饲养大鼠14d,建立高脂血症模型,各组大鼠进行心肌缺血再灌注实验,观察高脂血症和GSL对大鼠心肌缺血再灌注2h后血丙二醇(MDA),超氧化物歧化酶(SOD)和一氧化氮(NO)水平的影响和对再灌注性心律失常发生率的影响。结果显示:(1)用胆固醇乳剂饲养大鼠14d,成功建立高脂血症模型。同时给予GSL14d有明显降脂作用。(2)高脂血症状态下,心肌缺血再灌注2h后,血MDA升高(p<0.01),SOD降低(p<0.01)和NO(p<0.05)降低,再灌注10min内RPAr的发生率增高。(3)GSL组再灌注后2h的血MDA降低,而SOD和NO水平显著升高;使RPAr发生率大为降低,无VF发生。实验显示高脂血症加重心肌缺血再灌注损伤和提高RPAr发生率及动物死亡率,GSL可减少高脂饮食大鼠脂质过氧化和诱导体内NO生成而减轻缺血再灌注心肌损伤,降低缺血再灌注性心律失常发生率。     

卡托普利对急性缺血心肌早期室性心律失常的影响

目的:观察卡托普利对急性心肌缺血早期在体电生理指标的改变,探讨卡托普利对急性心肌梗塞(AMI)早期心律失常的影响。方法:采用S1-S2程控电刺激方法同时测定无心肌缺血对照组(假手术对照组)、AMI早期缺血组(AMI组)和用卡托普利(浓度0.1mg·kg-1·min-1)灌流AMI早期缺血的卡托普利组对家兔心室易损期(VVP)、室颤阈(VFT)、舒张阈(DT)、有效不应期(ERP)、T波顶点与VVP外缘处的时间关系(TT-VVP)等电生理指标。结果:VVP、VFT、DT、ERP和TT-VVP在假手术对照组与AMI组和卡托普利组比较均有显著差异(P<0.01),AMI组与卡托普利组比较亦有显著差异(P<0.01),相对于假手术对照组,AMI组VVP延长,VFT和DT降低,ERP缩短,心室易损期外缘向T波方向延伸增加;相对于AMI组,卡托普利组早期VVP缩短,VFT相对升高,ERP相对延长,心室易损期外缘向T波方向延伸相对减少。结论:卡托普利对急性心肌梗塞早期室性心动过速和/或心室颤动的产生有抑制作用。     

心室纤颤阈值及其影响因素

心室纤颤阈值VFT(ventricular fibrillation threshold)是反映心肌电稳定性的一项可靠指标。本文概要地介绍了电刺激方法测定VFT的意义、方法和影响因素。综述心率的变化、心肌缺血、神经系统、心律失常和酸硷电解质失调情况下对VFT的影响。     

Na^＋—K^＋—ATP酶抑制与心肌缺血后再灌注性损伤

在离体大鼠心脏灌流模型上,观察细胞内高钠对心肌缺血后再灌注性损伤的影响。在低灌流过程中,给予Na~ -K~ -ATP酶抑制剂哇巴因造成细胞内高Na~ ,可加重缺血后再灌注心脏的血液动力学障碍;增加心肌组织丙二醛含量及冠脉流出液中乳酸脱氢酶的活性;降低线粒体及胞浆液中谷胱甘肽过氧化物酶活力;并使心肌组织中Ca~(2 )超负荷及K~ 丢失严重。因此,细胞内高Na~ 可能是心肌缺血后再灌注损伤的基础。     

氧自由基与再灌性心律失常

心肌自律性的变化,或由于形成兴奋折返回路,均可诱发 RIA。缺血和再灌时可引起一系列生化和离子变化,其中氧自由基的产生,在诱发 RIA 中的作用,目前已进行了大量实验研究。超氧阴离子(·O_2~-)和氢氧自由基(·OH)在缺血心肌再灌或再给氧时可大量产生。这些高反应能力的氧自由基可使心肌细胞膜脂质发生过氧化作用,引起膜的完整性、流动性和通透性的有害变化,从而导致心律失常。     

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。     

钙离子对心脏的反常作用

“钙离子反常作用”是在离体灌流的动物心脏先用无钙灌流液(除Ca~(2+)缺乏外其它成分均正常)灌流一定时间,继而恢复正常灌流时所观察到的一种严重心肌损害现象。该现象的发生可能是由于恢复正常灌流时Ca~(2+)的大量快速内流造成细胞Ca~(2+)过荷所致;而无钙灌流则使细胞膜超微结构和通透性发生变化,对Ca~(2+)通透性显著增高。     

姜黄提取物对大鼠急性心肌缺血模型SOD的影响

为研究姜黄提取物对大鼠急性心肌缺血模型SOD的影响,本实验以大鼠急性心肌缺血模型为研究对象,采用SOD试剂盒测定血浆红细胞SOD和组织内SOD的含量以反映组织细胞内SOD的水平,间接了解体内氧自由基生成速率和脂质过氧化反应程度。结果表明：姜黄提取物能升高大鼠急性心肌缺血模型动物的血清和心肌组织SOD的含量。     

超氧化物歧化酶对内皮细胞缺氧复氧损伤的防护作用

体外培养扔兔胸主动脉内皮细胞缺氧３０ｍｉｎ后复氧１０ｍｉｎ,可以发现缺氧后复氧可引起细胞乳酸脱氢酶释放量,细胞悬液丙二醛含量增加,谷胱甘肽过氧化酶活性降低,细胞合成释放一氧化氮减少,细胞内钙离子浓度明显升高;ＥＣ的这些损伤在缺氧期间即有表现,复氧后更为加剧。而在缺氧前预先加入终浓度为２００Ｕ／ｍｌ的超氧化物歧化酶可改善细胞的抗氧化能力,减轻缺氧复氧对ＥＣ的损伤。     

Hypoxia/reoxygenation alters endothelial prostacyclin synthesis--protection by superoxide dismutase

An in vitro model was designed to study the role of ischemia/reperfusion and oxygen free radicals on vascular prostacyclin (PGI2) synthesis and protection provided by superoxide dismutase (SOD). Cultured bovine aortic endothelial cells (BAEC) were subjected to various times of hypoxia (30 min to 5 h) followed by 30 min reoxygenation. An increase or a decrease in PGI2 synthesis capacity was then observed according to the duration of hypoxia. Inhibition of PGI2 synthesis after 5 h hypoxia/30 min reoxygenation was accompanied by a rise in lipoperoxidation products and a slight cytotoxicity. Superoxide anion could be implicated in these cellular alterations as SOD efficiently prevented these effects. Incubation of normoxic or H/R-treated BAEC with SOD led to an increase in cellular SOD activity as compared to controls. This increase, inhibited by incubation at 4 degrees C but not by addition of cycloheximide, strongly suggested endocytosis of SOD. This study emphasizes the role of endothelium as a source and target of free radicals and provides a new insight into the mechanism of protection by SOD in ischemia-related vascular pathology.     

Protective effects of adenosine in rabbit sinoatrial node ischemia–reperfusion model in vivo: control of arrhythmia by hyperpolarization-activated cyclic nucleotide-gated (HCN)4 channels

Disturbance of cardiac rhythm is one of the consequences of myocardial ischemia/reperfusion injury. Many researchers have prompted considerable interests in developing therapeutic approaches for its control. In present study, we want to determine whether that adenosine pre- and postconditioning have protective effects on sinoatrial node ischemia/reperfusion injury on morphology, arrhythmia score, serological markers (CK-MB and cTnT), SOD activities, MDA levels and expression of HCN4 channels in SA node cells. According to the arrhythmia score recorded, whether adenosine used in terms of ischemia or reperfusion, the total number of arrhythmia was significantly reduced, as well as the number of its episodes was also markedly decreased. We have also shown a clear correlation between HCN4 channels expression and the dysfunction of SA node cells. HCN4 immunoreactivity decreased after adenosine pre- and postconditioning, but changes were significantly smaller in the cells of the SA node compared with cells of I/R group. The content of cTnT, CK-MB and MDA in adenosine pre- and postconditioning group reduced significantly; but the level of SOD increased significantly. Histological examination and electron microscopy observations found in adenosine pre- and postconditioning group sinoatrial node injury also mitigated. These findings suggested that adenosine pre- or postconditioning were to reduce the incidence of ischemia/reperfusion arrhythmias, reduce myocardial ischemia reperfusion injury. The mechanism was to stabilize the SA node cells membrane and one possible mechanism involves modulation of HCN4 channels in pacemaker cells of the sinoatrial node.     

人参茎叶皂甙对高胆固醇饮食大鼠再灌注性心律失常和脂质过氧化的 …

To explore the effects of GSL on myocardial reperfusion arrhythmia and lipid superoxidation in high cholesterol diet rats. Hyperlipidemia model was set up with administered high cholesterol emulsion 15 ml/kg to rats orally for 14 days. In GSL group, rats were given GSL i.p. 75 mg/kg simultaneously when administered high cholesterol emulsion. The experiment of myocardial ischemia reperfusion was performed on all rats. The results showed: (1) After administration of high cholesterol emulsion to rats orally for 14 days, hyperlipidemia model was set up successfully, simultaneously treatment with GSL. It lowered serum lipid; (2) In hyperlipidemia state, serum MDA increased (p < 0.01, SOD and NO decreased markedly (p < 0.01 and p < 0.05 respectively) after 2 h of myocardial reperfusion; the rate of reperfusion arrhythmia (RPAr) increased within 10 min of reperfusion, four out of nine rats died of ventricular fibrillation (VF); and (3) GSL decreased MDA, increased SOD and NO after 2 h of myocardial reperfusion. All changes were significant (p < 0.01); the rate of RPAr decreased, no VF occurred and all rats survived. Hyperlipidemia aggravated myocardial ischemia reperfusion injury and increased the incidence of RPAr. The results suggested that GSL reduced myocardial ischemia reperfusion injury and RPAr in high cholesterol diet state through antiperoxidating and inducing the production of NO.     

Lipid peroxidation and alterations to oxidative metabolism in mitochondria isolated from rat heart subjected to ischemia and reperfusion.

Ischemia-reperfusion injury to cardiac myocytes involves membrane damage mediated by oxygen free radicals. Lipid peroxidation is considered a major mechanism of oxygen free radical toxicity in reperfused heart. Mitochondrial respiration is an important source of these reactive oxygen species and hence a potential contributor to reperfusion injury. We have examined the effects of ischemia (30 min) and ischemia followed by reperfusion (15 min) of rat hearts, on the kinetic parameters of cytochrome c oxidase, on the respiratory activities and on the phospholipid composition in isolated mitochondria. Mitochondrial content of malonyldialdheyde (MDA), an index of lipid peroxidation, was also measured. Reperfusion was accompanied by a significant increase in MDA production. Mitochondrial preparations from control, ischemic and reperfused rat heart had equivalent Km values for cytochrome c, although the maximal activity of the oxidase was 25 and 51% less in ischemic and reperfused mitochondria than that of controls. These changes in the cytochrome c oxidase activity were associated to parallel changes in state 3 mitochondrial respiration. The cytochrome aa3 content was practically the same in these three types of mitochondria. Alterations were found in the mitochondrial content of the major phospholipid classes, the most pronounced change occurring in the cardiolipin, the level that decreased by 28 and by 50% as function of ischemia and reperfusion, respectively. The lower cytochrome c oxidase activity in mitochondria from reperfused rat hearts could be almost completely restored to the level of control hearts by exogenously added cardiolipin, but not by other phospholipids nor by peroxidized cardiolipin. It is proposed that the reperfusion-induced decline in the mitochondrial cytochrome c oxidase activity can be ascribed, at least in part, to a loss of cardiolipin content, due to peroxidative attack of its unsaturated fatty acids by oxygen free radicals. These findings may provide an explanation for some of the factors that lead to myocardial reperfusion injury.     

Detection of Free Radicals and Cholesterol Hydroperoxides in Blood Taken from the Coronary Sinus of Man During Percutaneous Transluminal Coronary Angioplasty

Patients undergoing percutaneous transluminal coronary angioplasty (PTCA) were investigated for the production of free radicals and cholesterol hydroperoxides during reperfusion. Fifteen patients were studied. Ischaemia during balloon inflation was assessed by serial coronary sinus lactate analysis (mean maximal increase in anterior descending artery diltation was 130%), and by the demonstration of reperfusion hyperaemia (mean increase of coronary sinus oxygen saturation 74%).

Free radicals were detected by electron spin resonance (ESR) spin trapping using the spin trap PBN (N-t-Butyl-α-phenylnitrone). Radical adducts were detected in up to 50% of samples taken during reperfusion after anterior descending lesion angioplasty. No radicals were detected in control samples or during the ischaemic phase. Radical detection was positively correlated with the change in coronary sinus lactate (p<0.025).

Coronary sinus cholesterol hydroperoxide analysis did not show a significant increase over control during reperfusion, due in part to unexpectedly high pre angioplasty levels.

This study provides clear evidence for the production of a burst of free radicals and evidence for lipid peroxidation in the minutes following myocardial reperfusion during angioplasty. A relationship between the severity of the ischaemic insult and the detection of radical adducts has also been found.     

Occurrence of oxidative stress during myocardial reperfusion

Reperfusion, without doubt, is the most effective way to treat the ischaemic myocardium. Late reperfusion may however cause further damage. Myocardial production of oxygen free radicals above the neutralizing capacity of the myocytes is an important cause of this reperfusion damage. There is evidence that prolonged ischaemia reduces the naturally occurring defence mechanisms of the heart against oxygen free radicals, particularly mitochondrial manganese superoxide dismutase, and intracellular pool of reduced glutathione. Consequently, reperfusion results in a severe oxidative damage, as evidenced by tissue accumulation and release of oxidized glutathione.An oxygen free radical-mediated impairment of mechanical function also occurs during reperfusion of human heart. In fact we observed during surgical reperfusion of coronary artery disease (CAD) patients, a prolonged and sustained release of oxidized glutathione;the degree of oxidative stress was inversely correlated with recovery of mechanical and haemodynamic function. These findings represent the rationale for therapeutic interventions which increase the cellular antioxidant capacities and improve the efficacy of myocardial reperfusion.     

卡托普利防治心肌胆厚的效应及其机理探讨

目的和方法：应用大鼠腹主动脉狭窄心肌厚模型,观察血管紧张素转换酶抑制剂卡托普利防治心肌肥厚的作用,以及该作用与心肌组织内儿茶酚胺、氧自由基、相关离子代谢之间的关系。结果：①应用卡托普利后,大鼠HW、LVW、HW／BW、LVW／BW各指标与心肌肥厚组比较均明显降低;②卡托普利可明显抑制心肌NE、DA含量的降低,E含量的增高;③卡托普利可增强心肌组织SOD和GSH－Px活性,减少LPO的生成;④卡托普利可明显抑制心肌Na^ 、Ca^2 含量的升高和心肌K^＋含量的降低。结论：卡托普利能有效防治心肌肥厚的发生,其作用机理不仅与卡托普利直接抑制体内RAS代谢有关,而且还与它调整和改善了心脏局部儿荷酚、氧自由基、相关离子代谢密切相关。