Infarct size-limiting effect of calcium preconditioning in rabbit hearts

Recent studies demonstrated that brief period of Ca2+ depletion and repletion (Ca2+ preconditioning, CPC) has strong protective effects against ischemia in a rat heart. CPC and classic preconditioning (IPC) were compared in relation with infarct size and protein kinase C (PKC) isozymes. Isolated Langendorff-perfused rabbit hearts were subjected to 45-min ischemia (Isc) followed by 120-min reperfusion (R) with or without IPC, induced by 5-min Isc and 10-min R. In the CPC hearts, 5-min Ca2+ depletion and 10-min repletion (CPC) were given before 45-min Isc, with or without concurrent PKC inhibition (calphostin C, 200 nmol/L). IPC enhanced recovery of LV function, while CPC did not. Infarct size was significantly reduced by both CPC and IPC (p < 0.05 vs. ischemic control). Membrane PKC was significantly increased from 2.53 +/- 0.07 (baseline, nmol/g tissue) to 3.11+/-0.07, 3.34 +/- 0.11, 3.15 +/- 0.09, and 3.06 +/- 0.08 by IPC, IPC and 45-min Isc, CPC and 45-min Isc, respectively (p < 0.01). Immunoblots of membrane PKC were increased by IPC, IPC and 45-min Isc, and CPC. These effects were abolished by PKC inhibition. Thus, activation of PKC may have trigger role in the mechanism of cardioprotective effect by CPC.     

Attenuation of conduction delay by ischemic preconditioning reduces ischemia-induced ventricular arrhythmias

Ischemic preconditioning has been acknowledged as a powerful method of decreasing ischemic injury. However, the antiarrhythmic mechanism of ischemic preconditioning during ischemia is unclear. We studied the effects of ischemic preconditioning on arrhythmias and cardiac electrophysiology during ischemia in Langendorff rat hearts (n = 44). In the non-preconditioned group (PC(-); n = 24), the hearts underwent 5-min zero-flow global ischemia without any prior ischemic preconditioning. In the preconditioned group (PC(+); n = 20), the hearts were preconditioned by three cycles of 3-min zero-flow global ischemia and 5-min reperfusion before undergoing 5-min global ischemia. Ischemic preconditioning reduced the incidence of ischemia-induced arrhythmias (PC(-); 38.9%, PC(+): 8.3%, p < 0.05), shortened monophasic action potential duration (MAPD, P < 0.05), attenuated conduction delay (conduction time; PC(-): 234.2%, PC(+): 173.4%, P < 0.05) and increased the ventricular fibrillation threshold. Although the shortening of MAPD in PC(-) hearts was not influenced by the presence or absence of arrhythmias, conduction time prolongation at 3-min was more obvious in PC(-) hearts with arrhythmia than in PC(-) hearts without arrhythmia (PC(-) with arrhythmia: 220.2%, PC(-) without arrhythmia: 190.7%, P < 0.05). We concluded that ischemic preconditioning could protect the rat hearts from ischemia-induced arrhythmias and postulated that attenuation of conduction delay during ischemia might be an important factor in the antiarrhythmic action of ischemic preconditioning.     

银杏达莫注射液抑制大鼠离体心脏缺血/再灌注损伤的机制研究

 目的：观察银杏达莫注射液预处理对大鼠离体心脏缺血/再灌注损伤的影响,并探讨其可能的作用机制。方法：SD雄性大鼠40只随机分成5组（n=8）：正常对照（NC）组、缺血/再灌注（I/R）组、缺血预处理（IPC+I/R）组、银杏达莫注射液预处理（GD+I/R）组和银杏达莫+氯化镧预处理（GD+LaCl3+I/R）组。观察各组相同时点（预灌30 min稳定点,缺血30 min,再灌5 min、30 min、60 min）的心功能指标,包括心率(HR)、左室收缩压(LVSP)和室内压变化速率（±dp/dtmax）,同时收集各时点冠脉流出液,检测其中乳酸脱氢酶（LDH）和肌酸激酶（CK）活性。实验结束后检测心肌线粒体Ca2+浓度和α-酮戊二酸脱氢酶（α-OGDH）含量。结果：与I/R组比较,IPC+I/R组和GD+I/R组在心脏再灌注期各项心功能指标均得到改善（P<0.05）;心肌LDH和CK的释放量降低（P<0.01）;线粒体内Ca2+超载降低（P<0.01）,且线粒体内α-OGDH含量升高（P<0.05）;而GD+I/R组中银杏达莫对心肌的保护作用被LaCl3抑制（P<0.05）。结论：银杏达莫可能通过抑制钙超载、增强线粒体酶活性以稳定线粒体能量代谢,从而缓解缺血/再灌注诱导的心肌细胞损伤。     

大鼠在体心脏缺血后处理模型的建立与优化

目的建立并优化大鼠在体心脏缺血后处理(I-postC)模型。方法采用冠状动脉左前降支垫扎球囊法建立在体心脏I-postC模型,健康雄性SD大鼠随机分为7组(n=8):缺血/再灌注(I/R)组(冠状动脉左前降支缺血45min/再灌注2h)、缺血预处理(IPC)组(I/R前先行3轮缺血5min/再灌注5min处理)、I-postC组(包括4个亚组,于冠脉缺血45min后先进行3或4轮再灌注30s/缺血30s或再灌注60s/缺血60s后处理后再进行冠脉再灌注)以及假手术(sham)组。氯化三苯四氮唑(TTC)法测定心肌梗死面积,试剂盒检测血浆乳酸脱氢酶(LDH)和心肌组织超氧化物歧化酶(SOD)活性。结果I/R引起明显的心肌梗死和组织损伤,采用冠状动脉左前降支垫扎球囊法进行I-postC可以显著减少I/R后心肌梗死面积,尤以3或4轮再灌注30s/缺血30s组保护作用明显,其梗死区占缺血区百分比分别比I/R组下降30.26%和58.81%(P分别<0.05),与IPC保护效果相近。结论I-postC可以减轻心肌I/R损伤,其中4轮再灌注30s/缺血30s诱导的I-postC在限制心肌梗死面积方面作用最明显,是理想的大鼠在体心脏I-postC模型。     

非创伤性预处理在离体心脏抗再灌注损伤中作用机制的探讨

目的:观察非创伤性肢体缺血预处理对大鼠离体再灌注心肌是否有保护作用。方法:实验采用体重(250±30)gSD雄性大鼠25只随机分成3组,在Langendorff装置上对大鼠离体心脏进行灌流。对照组(C,n=8):在灌注全程均用富氧K-H液(充以95%O₂+5%CO₂),在恒压(8.33kPa)、恒温(37℃)条件下灌注;缺氧/复氧组(A,n=8):预灌15min后,灌注心脏先全心缺血缺氧15min,随后15min复氧再灌注(37℃);非创伤性肢体缺血预处理组(N-WIP,n=9):先将大鼠双后肢捆绑5min,松开5min,反复4次后,随后的方法同R组。在相应时点分别测定冠脉流出液和心肌匀浆中超氧化物歧化酶(SOD)活性,Ca²⁺-Mg²⁺-ATP酶活性和丙二醛(MDA)含量,同时记录心肌细胞的单相动作电位(MAP)和心肌收缩张力曲线。结果:非创伤性肢体缺血预处理能使再灌注心律失常发生率显著低于A组;心肌组织中MDA含量显著低于A组,心肌组织中SOD活性显著高于A组,心肌细胞的膜电位、Ca²⁺-Mg²⁺-ATP酶活性及肌张力较稳定。结论:非创伤性肢体缺血预处理对大鼠离体再灌注心肌有明显的保护作用,可能是通过增强心肌的抗氧化能力、稳定心肌Ca²⁺-Mg²⁺-ATP酶活性和膜相结构等途径,提高心肌细胞对再灌注损伤的抵抗力。     

Does nitric oxide generation contribute to the mechanism of remote ischemic preconditioning?

The protective effect of local or remote ischemic preconditioning (IPC) on subsequent 40-min ischemic and 120-min reperfusion myocardial damage was investigated. Preconditioned rats underwent one cycle of myocardial ischemia/reperfusion consisting of 5-min ischemia produced as a left coronary artery (LCA) occlusion and 5 min of reperfusion. Remote IPC was produced as 15 min of small intestinal ischemia with 15 min of reperfusion as well as 30 min of limb ischemia with 15 min of reperfusion. A marked protective action was afforded by both IPC protocols with a more significant effect of local (classic) ischemic preconditioning. Since the protective effect of remote IPC was not abolished by nitric oxide (NO) synthase inhibition with Nω-nitro- -arginine ( -NNA) it is concluded that NO generation may not be involved in the mechanism of remote IPC.     

缺血预处理延缓大鼠心肌缺血引起的细胞间电脱耦联

目的:研究缺血预处理(IPC)延缓心肌细胞间电脱耦联现象及其可能的机制,尤其是线粒体膜ATP敏感性钾通道(mitoK_ATP)在其中的作用。方法:大鼠心脏Langendorff离体灌流,用四电极法测量心肌整体阻抗(R_t),监测R_t在心肌缺血后的变化来判断心肌细胞发生电脱耦联的时间。结果:(1)对照组心肌缺血40 min后复灌30 min,心肌细胞间电脱耦联发生平均时间为(13.29±0.95) min;(2)IPC可以明显延迟电脱耦联的发生时间、促进心肌缺血复灌后收缩功能的恢复;(3)IPC前给予mitoK_ATP特异阻断剂5-hydroxydecanoate(5-HD,100 μmol/L)取消了IPC的心脏作用;(4)MitoK_ATP特异开放剂diazoxide(60 μmol/L)预处理可以模拟IPC延迟电脱耦联、促进心肌收缩功能恢复;(5)Diazoxide的IPC模拟作用能被5-HD取消,也能被L型钙通道特异阻断剂verapamil(2.0 μmol/L)和自由基清除剂N-(2-mercaptopropionyl)glycine(300 μmol/L)取消。结论:IPC可以通过激活mitoK_ATP延缓大鼠心肌缺血造成的细胞间电脱耦联和改善心肌收缩功能。     

米力农预调对兔心肌的保护作用

目的 探讨米立农预调对成年兔心肌缺血后损伤的保护作用.方法 采用Langendorff离体心脏灌注模型,对32只成年兔随机分为4组进行不同方法预调心肌保护:缺血预调(IPC)、氨力农预调(APC)、米力农预调(MPC),并与单纯全心缺血-再灌注(GI)对照.所有动物均全心缺血30min,开放后再灌注90 min.结果 4组心肌梗死量分别为MPC(10.2±0.7)%、APC(12.8±0.9)%、IPC(23.5±1.5)%和GI(31.2±2.7)%,前两组和后两组比较.差异有统计学意义(P<0.05);前两组左心功能(LVPDP、+dp/dt、LVEDP)恢复亦明显优于后两组(P<0.05).结论 米力农能发挥预调作用,效果与氨力农相当,有可能成为一种新的有效的心肌保护方法.     

缺血预处理对缺血/再灌注脑的保护及其与微循环调节功能的关系研究

目的:探讨缺血预处理(IPC)是否对缺血/再灌注(I/R)脑细胞具有保护效应及其与微循环调节功能间的关系。方法:I/R与IPC组大鼠均复制脑I/R损伤模型,IPC组增加于I/R之前24h进行的短暂脑缺血预处理。动物均开颅窗观察缺血前、缺血后、再灌后脑软膜微循环指标;并取脑组织作红四氮唑(TTC)染色观察缺血损伤情况。结果:I/R组TTC染色后大多数出现不规则的缺血损伤的淡染区,而IPC组明显少见。IPC组缺血及再灌之后毛细血管累计总长度、微循环血流量、微血管内血流速度之相对增加值均大于I/R组。I/R组于再灌注之后有无复流现象;而IPC组此时呈灌注增加的过程。结论:IPC通过提高微循环的调节功能,促进毛细血管的相对性开放和血流的相对性加快,减轻缺血期组织血流低灌注和再灌注期无复流现象,从而对I/R脑产生一定保护作用。     

Changes in catecholamine, angiotensin converting enzyme and adenosine triphosphatase in ischemic preconditioning rat hearts

Changes in catecholamine ,angiotensin converting enzy me and adenosine triphosphatase in ischemic preconditioning rat hearts     

凝集素在大鼠心脏缺血预处理中的应用

目的：实验拟通过刀豆素（ＣＯＮＡ）和麦芽素（ＷＧＡ）检测缺血再灌注损伤大鼠心肌和缺和缺血预处理大鼠心肌细胞膜凝集素受体的变化。方法：采用ＳＤ雄性大鼠１８只分３组：假手术组、缺血再灌注组、缺血预处理线,分别取三组大鼠左心室前壁心肌,常规石蜡包埋切片,分别用刀豆素、麦芽素分子探针进行ＡＢＣ法染色。结果：假手术组ＣＯＮＡ和ＷＧＡ细胞反应强,缺血再灌注组ＣＯＮＡ和ＷＧＡ细胞反应弱。缺血预处理组ＣＯＮＡ和Ｗ     

NO参与缺血预处理对大鼠骨骼肌缺血再灌注损伤的保护作用

目的研究缺血预处理(IPC)对大鼠骨骼肌缺血再灌注损伤的保护作用及一氧化氮(NO)是否参与此保护作用。方法采用Wistar雌性大鼠,在左后肢跟部止血,同时使用血流监测仪测股四头肌的血流量,调整止血带的松紧程度,使血流量控制在上止血带前的30%。30只大鼠随机分成3组,分别为缺血再灌注组(n=10)、缺血预处理组(n=10)、缺血预处理+NAME组(n=10)。应用尼克酰胺腺嘌呤二核苷酸黄递酶2+2+(NADH)染色,检测股四头肌各型肌纤维横截面积,钙-腺苷三磷酸酶(Ca-ATPase)染色,观察细胞膜CaATPase分布。透射电镜观测肌细胞的超微结构变化。结果缺血再灌注组出现明显肌纤维破裂溶解,许多白细胞浸润,电镜下线粒体中含有大量空泡变性、肌纤维断裂、溶解和"Z线"排列整齐膜脂质过氧化物的增加。与缺血再灌注组相比,缺血预处理组显示了轻微的损害,正常的纤维和血管变形少,股四头肌各型肌纤维横2+截面积降低,细胞膜Ca-ATPase数量增加。缺血预处理+NAME组与缺血再灌注组相比没有明显改变。结论缺血预处理对大鼠骨骼肌缺血再灌注损伤有明显保护作用,NO参与这一保护作用。     

Preconditioning of the Small Intestine to Ischemia in Rats

Measures reflecting the state of the small intestine were studied in rats after ischemia lasting 90 min produced by clamping the superior mesenteric artery and reperfusion for 30 min. Preconditioning of the intestine to ischemia was induced by producing intestinal ischemia for 10 min followed by 10 min of reperfusion (ischemic preconditioning), 30-min limb ischemia with 15-min reperfusion (distant ischemic preconditioning), and i.v. L-arginine. The smallest amount of damage to the intestine after 90 min of ischemia and 30 min of reperfusion was seen in the group of rats subjected to ischemic preconditioning. The protective effect of ischemic preconditioning was partially blocked by administration of N--nitro-L-arginine (a blocker of NO synthesis). Doses of L-arginine also had protective effects, though these were smaller than those of ischemic preconditioning. Preliminary ischemia-reperfusion of the limb had no effect on the state of the intestine. Thus: 1) ischemic preconditioning of the intestine is partially associated with activation of nitric oxide synthesis, and 2) distant ischemic preconditioning did not protect the intestine.     

Bone Morphogenic Protein-7 Contributes to Cerebral Ischemic Preconditioning Induced-Ischemic Tolerance by Activating p38 Mitogen-Activated Protein Kinase Signaling Pathway

Cerebral ischemic preconditioning (IPC), which refers to a transient and noninjurious ischemia is able to induce tolerance against the subsequent lethal ischemia, including ischemic stroke. We have previously reported that bone morphogenic protein-7 (BMP-7) contributes to the neuroprotective effects of IPC-induced ischemic tolerance, and thus ameliorates the following ischemia/reperfusion (I/R) injury in rats. Consequently, in the present study, we continued to explore the underlying regulatory mechanisms involved in BMP-7-mediated cerebral IPC in the rat model of ischemic tolerance. Male Wistar rats were preconditioned by 15-min middle cerebral artery occlusion (MCAO). After 2-day reperfusion, these animals were subjected to prolonged MCAO for 2 h. Our results showed that the phosphorylated p38 mitogen-activated protein kinase (MAPK) paralleling to BMP-7 was up-regulated by IPC in rat brain. Inactivation of p38 MAPK by pretreatment of SB203580, a p38 MAPK-specific suppressor, weakened the protective effect of IPC on CA1 neurons. Moreover, the enhanced phosphorylation of p38 MAPK induced by IPC was attenuated when the endogenous BMP-7 was inhibited by BMP-7 antagonist noggin. Besides, blockade of p38 MAPK signal transduction pathway via SB203580 abrogated the protective effects of exogenous BMP-7 against cerebral infraction. These present findings suggest that BMP-7 contributes to cerebral IPC-induced ischemic tolerance via activating p38 MAPK signaling pathway.     

细胞间黏附分子-1抑制参与大鼠小肠缺血后处理的保护作用

目的观察缺血后处理（I-postC）对缺血／再灌注（I／R）大鼠小肠组织细胞间黏附分子-1（ICAM-1）表达和髓过氧化物酶（MPO）活性的影响，探讨其减轻I／R损伤的机制。方法32只健康雄性Wistar大鼠随机分为假手术（Sham）、I／R、I-postC及缺血预处理（IPC）组，以无创动脉夹夹闭肠系膜上动脉建立小肠I／R损伤模型，常规制备病理切片，光镜下观察肠组织损伤情况。试剂盒测定MPO、超氧化物歧化酶（SOD）活性及丙二醛（MDA）含量，免疫印迹法检测小肠组织ICAM-1和NF-κBP65的表达。结果I-postC明显减轻I／R导致的小肠组织病理变化，抑制I／R所致的小肠组织MPO活性和MDA含量升高（分别为I／R组的68．7％和77、1％，P〈0.05），上调SOD活性（为I／R组的1．2倍，P〈0.05），并下调小肠组织NF-κBP65和ICAM-1表达（分别较I／R组低44．3％和49．0％，P〈0．01）。结论I-postC通过抑制ICAM-1表达和中性粒细胞游出而减轻小肠I／R损伤。     

大鼠心脏腺苷预处理心肌组化和细胞化学变化

目的：应用图象分析和电镜细胞化学方法,观察大鼠心脏腺苷预处理心肌琥到脱氢酶、细胞色素氧化酶及Ｃa＾２＋Ｍg＾２＋－ＡＴＰase活性变化。方法：采用ＳＤ雄性大鼠３２只 分４组,即正常对照组（ＮＣ）,缺血/再灌组（Ｉ/Ｒ）,缺血预处理组,腺苷预处理组。用图象分析检测琥珀酸脱氢酶、细胞色素氧化酶和Ｃa＾２＋Ｍa＾２＋－ＡＴＰase活性。 结果：在缺血预处理组及腺苷预处理组琥珀酸脱氢酶、细胞色素氧化酶、Ｃa＾２＋Ｍa＾２     

延迟预适应对缺血再灌注损伤冠状动脉内皮细胞的保护作用

目的:研究延迟缺血预适应(IPC)对缺血再灌注(I/R)冠状动脉内皮细胞的保护作用。方法:所有动物随机分为三组:假手术组(CON组,n=6),缺血再灌注组(I/R组,n=6),预适应组(IPC组,n=6)。I/R组及IPC组分别于不同时间段抽血检测NO、丙二醛(MDA)及超氧化物歧化酶(SOD)的含量。实验结束后,取心脏左前降支(LAD)所支配的心肌组织一小块,行免疫组化染色。结果:IPC组NO缺血前明显高于开胸后,缺血前IPC组高于I/R组;MDA含量缺血前及再灌注后IPC组均低于I/R组;SOD的活性,再灌注后两组差异显著。IPC组内皮型一氧化氮合成酶(eNOS)的表达明显高于I/R组。结论:延迟预适应早期内皮细胞生成NO的量增加,自由基减少,且保护后期的再灌注中NO、自由基的量处于相对稳定,同时使内皮中SOD的活性及eNOS的表达增加。     

非创伤性预处理对大鼠缺血心脏的保护效应

目的 :探讨三种非创伤性预处理对大鼠缺血心脏的保护效应。方法 :采用 2 5 0g～ 3 0 0 gSD雄性大鼠 48只 ,分成 6组 ,即假手术组(Ⅰ组 )、缺血 /再灌组 (Ⅱ组 )、经典缺血预处理组 (Ⅲ组 ) ,缺氧预处理组 (Ⅳa组 )、后肢缺血预处理组 (Ⅳb组 )、去甲肾上腺素预处理组 (Ⅳc组 ) ,观察各组左室梗塞范围、心肌琥珀酸脱氢酶 (SDH )、Ca2 + Mg2 + ATPase、细胞色素氧化酶 (CCO)活性的变化。结果 :Ⅳa、Ⅳb、Ⅳc三组非创伤性预处理均可明显缩小左室梗塞范围、提高心肌SDH、Ca2 + Mg2 + ATPase、CCO酶活性。结论 :三种非创伤性预处理均能使大鼠显示和经典预处理相类似的心脏保护效应。     

延迟预适应对兔心脏缺血再灌注损伤保护作用的研究

目的:观察延迟缺血预适应(IschemicPreconditioning,IPC)对兔在体心脏缺血再灌注(Ischemia/Reperfusion,I/R)损伤的保护作用。方法:方法18只兔随机分为3组:假手术组(CON组,n=6),缺血再灌注组(I/R组,n=6),预适应组(IPC组,n=6)。采用免疫组化方法检测诱导型一氧化氮合成酶(iNOS)及内皮型一氧化氮合成酶(eNOS)在心肌及冠状动脉内皮中的表达情况。结果:IPC组的梗死面积明显小于I/R组。在心肌中,IPC组iNOS表达明显高于I/R组与CON组,而eNOS无显著性差异。在内皮中,IPC组eNOS表达明显高于I/R组,与CON组无显著性差异,而iNOS均无表达。结论:延迟缺血预适应能缩小兔缺血再灌注后心肌梗死面积。     

Relation between ischemic preconditioning and the duration of sustained ischemia.

It has been reported that repetitive brief periods of ischemia and reperfusion (ischemic preconditioning, IP) cause a significant reduction in the extent of myocardial necrosis or in the incidence of reperfusion arrhythmias in rat heart. However, recent reports have stated that IP effect is diminished or lost in the canine or bovine heart if ischemia (mostly regional) is sustained for 40 min or longer. The main objective of this study is to assess whether IP provides myocardial protection in prolonged sustained ischemia under the condition of global ischemia in isolated rabbit heart. The hearts were subjected to 10-60 min sustained ischemia (SI) followed by 60 min reperfusion with (IP heart) or without IP (ISCH heart). IP was induced by 4 cycles of 5 min global ischemia and 5 min reperfusion. Left ventricular function (LVF), extent of infarction (EI) and ultrastructural changes were examined. As a whole, the LVF began to recover on reperfusion but there was no significant difference in the functional parameters. However, extracellular Ca2+ concentration was lower in the ISCH hearts (p < 0.05) and the EI was significantly different between the hearts which had received 60 min SI (67% in the ISCH versus 32% in the IP heart, p < 0.01). Ultrastructural changes were homogeneous in the ISCH hearts and became irreversible in accordance with increase of the duration of ischemia, while these changes were heterogeneous and restricted in the IP heart. These results suggest that IP does not attenuate the postischemic dysfunction in prolonged ischemia but it can provide an infarct size-limiting effect and delay ultrastructural changes. This cardioprotective effect may be related to calcium homeostasis.