氨氯地平和依那普利对高血压大鼠肾损害的防治效果观察

目的　探讨钙拮抗剂氨氯地平 ( amlodipine)与转换酶抑制剂依那普利 ( enalapril)抗高血压治疗时对肾脏的保护作用。　方法　实验动物为 1 6月龄的自发性高血压大鼠 ( SHR) 3 0只 ,分为氨氯地平组、依那普利组及对照组 ,治疗及观察时间为 3个月。　结果　氨氯地平和依那普利降压效果相似 ,肾功能改变 :老化过程中对照组内生肌酐清除率 ( Ccr)为 ( 0 .0 90± 0 .0 1 0 ) ml· min- 1 ·1 0 0 g- 1体重 ,与实验前的 ( 0 .1 4 9± 0 .0 0 7) ml·min- 1· 1 0 0 g- 1体重比较显著降低 ( P<0 .0 1 ) ;两治疗组 Ccr无明显下降 ( P>0 .0 5) ,依那普利组为 ( 0 .1 57± 0 .0 0 3 ) ml· min- 1 · 1 0 0 g- 1 体重 ,氨氯地平组为 ( 0 .1 63± 0 .0 0 6) ml·min- 1· 1 0 0 g- 1体重。肾功能测验 ,N-乙酰 -β-D-氨基葡萄糖苷酶在对照组逐步增高 ,但两治疗组降低。血浆血管紧张素 水平与肾组织内皮素含量 :依那普利组〔( 2 52 .3± 3 3 .1 )ng/ L、( 1 2 2 .2± 3 3 .5) ng/ L〕与氨氯地平组〔( 1 87.3 2± 53 .1 ) ng/ L、( 1 51 .1± 2 2 .9) ng/ L〕均低于对照组〔( 3 83 .5± 84 .1 ) ng/ L、( 1 85.8± 1 4 .5) ng/ L〕( P<0 .0 1 )。肾病理改变 ,对照组明显重于治疗组。计算机图像分析 ,对照组肾小球系膜     

甲状腺素对在体兔心肌缺血再灌注损伤的影响

目的　研究甲状腺素 (TH)预处理对在体兔心肌缺血再灌注损伤的保护作用及其机制。方法　 1 8只日本大耳白毛兔随机分为假手术(shame- operate control,SC)组、心肌缺血再灌注 (myocardial ischemia reperfusion,MIR)组、TH+MIR组。结扎冠状动脉左前降支 2 0 min后再灌注 ,建立心肌缺血再灌注模型 ,动态监测心率、心律、左室功能指标。检测再灌注 60 min时血液及缺血区中央心肌组织三磷酸腺苷 (ATP)、乳酸 (LA)、游离脂肪酸 (FFA)、超氧化物歧化酶 (SOD)及丙二醛 (MDA)的含量及心肌超微结构的改变。结果　 SC组、MIR组及 TH+MIR组 LVSP、± dp/ dtmax、HR的基础值均无显著差异 ,再灌注 60 min时 ,TH+MIR组 LVSP、± dp/ dtmax、HR明显优于 MIR组 ;心肌 ATP含量 (0 .2 62± 0 .1 2 5)μmol· g- 1较MIR组 (0 .1 31± 0 .0 0 9) μmol· g- 1高 1倍 ,而心肌 LA、FFA及 MDA则显著低于 MIR组 ,电镜下超微结构优于 MIR组。结论　 TH预处理可促进缺血再灌注后左室功能的恢复 ,与其改善心肌能量代谢、抑制氧自由基形成及保护心肌超微结构有关。     

兔右冠状动脉缺血预适应对窦房结功能及房室传导有效不应期的影响

探讨兔右冠状动脉 (简称冠脉 )缺血预适应对缺血再灌注 (I/R)损伤时窦房结功能和房室传导有效不应期的影响。随机将 36只健康家兔分为正常对照组、单纯I/R损伤组 (IR组 )和缺血预适应组 (IP组 )。对照组只穿线不阻断血流 ;IR组右冠脉阻闭 6 0min ,继以再灌注 6 0min ;IP组阻闭右冠脉 5min后再灌注 10min ,再重复IR方案。在不同时相分别测定IR和IP组心房快速起搏或程序电刺激后的窦房传导时间 (SACT)、窦房结恢复时间 (SNRT)、最大起搏峰值 (PCLP)以及房室有效不应期 (AVERP) ,并以电镜观察右心超微结构。结果显示 :①IR及IP组的再灌注5min、IR组缺血 5min时的SACT均较正常对照组明显延长 ;②除IP组缺血 10min的SNRT及IP组再灌注 40min的AVERP外 ,两实验组的SNRT及PCLP值均较正常对照组明显延长 (P <0 .0 1) ;③IP组 4项电生理指标的改变程度均较同期的IR组明显减轻 (P <0 .0 5或 0 .0 1) ;④较之IR组 ,IP组的右心房肌超微结构损伤明显减轻。提示在体兔右冠状动脉IP可保护右房肌的超微结构 ,减轻I/R对窦房结功能及AVERP损伤。     

卡维地洛对大鼠缺血再灌注心肌细胞凋亡及基因表达的影响

目的 :研究卡维地洛对缺血再灌注心肌细胞凋亡及bcl 2、bax基因表达的影响 ,探讨卡维地洛抑制缺血再灌注心肌细胞凋亡的可能分子机制。方法 :结扎Wistar大鼠左冠状动脉前降支 (LAD) ,建立大鼠缺血再灌注动物模型。 30只大鼠分 3组 (每组 10只 ) :卡维地洛组 (卡维地洛治疗 )、缺血再灌注组和假手术组。用Tunnel法检测心肌细胞凋亡 ,并用光学显微镜进行细胞计数 ,免疫组化和原位杂交法检测bcl 2、bax基因表达 ,并利用图像分析系统检测二者的平均光密度值 (A值 ) ,进行定量分析。结果 :心肌细胞凋亡数在缺血再灌注组、假手术组和卡维地洛组分别为 36 .8± 9.0、0 .2± 0 .1和 9.5± 3.0 ,各组间差异有统计学意义 (P <0 .0 1)。缺血再灌注组、假手术组和卡维地洛组的bcl 2mRNAA值分别为 0 .0 6± 0 .0 1、0 .0 8± 0 .0 1和 0 .0 9± 0 .0 1,bcl 2蛋白平均A值分别为0 .0 8± 0 .0 2、0 .14± 0 .0 1和 0 .15± 0 .0 3,卡维地洛组与缺血再灌注组相比差异无统计学意义 (P >0 .0 5 ) ;缺血再灌注组bax蛋白的平均A值为 0 .13± 0 .0 2 ,假手术组为 0 .0 7± 0 .0 1,卡维地洛组为 0 .0 6± 0 .0 1,卡维地洛组与缺血再灌注组相比差异有统计学意义 (P <0 .0 5 ) ,bcl 2 /bax蛋白比值在缺血再灌注组、假手术组和卡     

大鼠肝脏缺血再灌注损伤中NO，TXA2/PGI2的作用

我们通过大鼠肝脏缺血再灌注损伤模型,对血管活性物质一氧化氮(nitric oxide,NO)以及血栓素A2/前列环素(TXA2/PGI2)的作用进行了探讨。 1 材料和方法 1.1 模型制备健康Wistar大鼠,雄性,体质量300g±30g(军事医学科学院实验动物中心提供),10g·L~(-1)戊巴比妥钠40mg·kg~(-1),ip麻醉,腹中线切口,小动脉夹夹闭肝动脉、门静脉及胆总管45min,解除阻断,肝脏缺血再灌注损伤模型制成,分别于再灌注不同时间点采取标本。手术对照组仅开腹采取标本,不做阻断。将实验动物随机分为5组,每组6只动物。手术对照组;肝脏缺血45min再灌注Oh组;肝脏缺血45min再灌注1h组;肝脏缺血45min再灌注3h组;肝脏缺血45min再灌注5h组。在再灌注同时自大鼠尾静脉注入左旋精氨酸(L-Arg)     

倒卵叶五加总皂甙对大鼠心肌缺血/再灌注损伤后细胞凋亡的作用及机制

目的　探讨倒卵叶五加总皂甙 (SAOH)对大鼠缺血心肌再灌注后细胞凋亡的作用。方法　采用结扎左冠状动脉前降支再灌注复制大鼠心肌缺血再灌注损伤 (IRI)的模型 ,结扎前 10 min舌下静脉注射 SAOH,测定心肌缺血3 0 min后再灌注 6h心肌组织丙二醛 (MDA)和血浆超氧化歧化酶 (SOD)的含量 ,并用末端脱氧核苷酸转移酶介导的带生物素的 d UTP缺口末端标记 (TUNEL)的方法及免疫组化观察左心室心肌细胞凋亡及凋亡相关基因 Bcl- 2和 Bax的蛋白表达。结果　再灌注 6h后 ,SAOH1 组 (5 0 mg/ kg)及 SAOH2 组 (10 0 mg/ kg)较 IRI组 ,心肌组织 MDA含量明显减少 [(4.89± 0 .2 6)、(3 .5 7± 0 .2 1) nm ol/ mg· pro vs(6.97± 0 .3 4) nmol/ mg· pro,P值均 <0 .0 1];血浆 SOD活性明显提高 [(9.88± 0 .18)、(11.40± 0 .3 7)μIU / L vs (3 .3 9± 0 .2 4)μIU / L ,P值均 <0 .0 1];心肌细胞凋亡指数 (AI)显著减少 [(14.67± 3 .0 5 ) %、(7.49± 2 .62 ) % vs(2 1.96± 7.68) % ,P值均 <0 .0 1];Bax蛋白表达明显减少 [(7.73± 1.84) %、(5 .0 2± 1.0 1) % vs (18.5 9± 5 .68) % ,P值均 <0 .0 1];而心肌 Bcl- 2蛋白的表达显著增加 [(12 .5 1± 3 .42 ) %、(17.48± 4.72 ) % vs(7.3 2± 2 .0 5 ) % ,P值 <0 .0 5 ,<0     

内皮素受体拮抗剂BMS-182874对大鼠心肌缺血再灌注损伤的保护作用

为观察选择性内皮素A受体拮抗剂BMS 182 874对离体灌注心脏缺血再灌损伤的影响 ,并进一步探讨其可能的作用机制。按照Langendorff方式灌注离体大鼠心脏 ,全心缺血 30min后再灌注 30min诱导急性心肌缺血模型。给予BMS 182 874 (10 μmol/L或 5 0 μmol/L)持续灌注离体心脏 ,连续记录心功能 ,检测冠状动脉流出液中的肌酸激酶和心肌组织中的肿瘤坏死因子α含量。结果发现 ,与对照组相比 ,缺血再灌注组心功能显著下降 ,左心室内压和左心室内压最大变化率 (±dp/dtmax)、冠状动脉流量明显降低 (P <0 .0 1) ,肌酸激酶 (2 3.9± 2 .2比 2 17.5± 14 .1,P<0 .0 1)以及心肌组织中肿瘤坏死因子α含量明显增加 (6 4 5± 4 5比 192 6± 14 1,P <0 .0 1) ,而 10 μmol/L和 5 0 μmol/L的BMS 182 874显著减轻缺血后心功能的损害 ,升高左心室内压和左心室内压最大变化率 (±dp/dtmax) (P <0 .0 1) ,同时降低肌酸激酶 (185± 14和 14 3± 11,与缺血再灌注组相比P <0 .0 5和P <0 .0 1)和心肌组织中的肿瘤坏死因子α含量 (12 2 2± 6 7和 110 8± 5 7,与缺血再灌注组相比P <0 .0 1)。结果提示 ,内皮素A受体拮抗剂能显著减轻心肌缺血再灌注损伤 ,其保护作用可能与抑制心肌组织中肿瘤坏死因子α生成有关。     

犬小肠缺血再灌注后氧自由基的改变意义

目的研究小肠小范围缺血再灌注后的氧自由基改变及其意义.方法阻断分布于较小范围的小肠动脉,于动脉阻断前、阻断开放后0,30及60min,从与阻断动脉伴行小肠静脉采集血液标本,检测其NO和SOD的浓度结果再灌注后,在0,30及60min的NO浓度分别是(12.1±4.6),(11.6±4.4),(15.5±4.8)μmol.L-1,SOD的浓度分别是(75.0±4.5),(43.4±11.4),(90.3±27.9)×103NU.L-1.NO和SOD的改变特点显示小肠再灌注后其浓度明显低于阻断前(25.6±4.0)μmol.L-1和(169.0±10.8×103NU.L-1,P＜0.01),在再灌注30mm为最底,而至再灌注60min则有明显的升高.结论小范围的小肠缺血再灌注而导致氧自由基升高和小肠损伤,与多脏器和大范围小肠缺血再灌注相比,虽然也很明显,但恢复较快.     

丹参注射液对大鼠心肌缺血再灌注时心肌细胞凋亡的影响

目的 :研究丹参注射液对大鼠心肌缺血再灌注时心肌细胞凋亡的影响。方法 :用在体左冠状动脉前降支穿线结扎法制备心肌缺血再灌注模型。 6 0只SD大鼠分为 3组 :假手术组 (10只 ) ,缺血再灌注组 (2 5只 ) ,丹参注射液干预组 (2 5只 )。缺血 30min ,再灌注 12 0min。采用缺口末端标记法 (TUNEL)以及S P免疫组化法 ,检测心肌细胞凋亡指数 (AI)、Bcl 2、Bax基因蛋白表达。结果 :假手术组AI 2 .2± 0 .6 ,Bcl 2OD值 0 .112± 0 .0 18,BaxOD值 0 .10 2± 0 .0 31;缺血再灌注组AI 2 8.9± 3.6 ,Bcl 2OD值 0 .0 92± 0 .0 14 ,BaxOD值 0 .136± 0 .0 2 2 ;丹参注射液干预组AI 2 6 .2± 3.4 ,Bcl 2OD值 0 .10 4± 0 .0 2 1,BaxOD值 0 .12 2± 0 .0 12。与假手术组比较 ,缺血再灌注组AI增加 ,Bax阳性表达增强 ,Bcl 2阳性表达减弱 (P <0 .0 1) ;与缺血再灌注组比较丹参注射液干预组 ,AI、Bax阳性表达下降 (P <0 .0 1) ,Bcl 2阳性表达上调 (P <0 .0 5 )。结论 :丹参注射液通过抑制心肌细胞凋亡 ,下调Bax基因蛋白表达 ,上调Bcl 2基因蛋白表达 ,起到心肌缺血再灌注损伤的保护作用。     

氯沙坦和卡维地洛对缺血再灌注心肌细胞凋亡的影响

目的 :研究氯沙坦和卡维地洛对缺血再灌注心肌细胞凋亡的影响 ,比较氯沙坦和卡维地洛对缺血再灌注心肌损伤的保护作用。方法 :结扎Wistar大鼠左冠状动脉前降支 ,建立大鼠缺血再灌注动物模型 ,采用原位末端标记细胞凋亡法检测心肌细胞凋亡 ,并利用光学显微镜进行细胞计数。结果 :单纯缺血 再灌注组心肌细胞凋亡数较假手术组明显增多 (37.5 3± 9.2 2 /视野∶0 .18± 0 .0 9/视野 ,P <0 .0 5 ) ,氯沙坦和卡维地洛组心肌细胞凋亡数分别为 8.74± 3.5 1/视野和 7.6 3± 4 .0 5 /视野 ,较单纯缺血 再灌注组明显减少 (P <0 .0 5 ) ,氯沙坦和卡维地洛两组间无明显区别 (P >0 .0 5 )。结论 :氯沙坦和卡维地洛对缺血再灌注心肌细胞损伤具有相似的保护作用 ,可明显减少缺血再灌注心肌细胞凋亡     

薯蓣皂甙对大鼠心肌缺血再灌注损伤的保护作用

目的观察薯蓣皂甙对大鼠心肌缺血再灌注(IR)损伤的保护作用。方法健康雄性Wistar大鼠48只,随机分为IR组、高剂量组(DH)、低剂量组(DL)。IR组0.9%生理盐水10m.lkg-1.d-1灌胃,高剂量组薯蓣皂甙300mg·kg-1.d-1灌胃,低剂量组150mg·kg-1.d-1灌胃,共7d。末次给药24h后,复制大鼠心肌IR损伤模型,观察心脏生理学指标(HR、BP、ST段变化),心律失常评分,心肌梗死面积,心肌形态学指标的变化。结果与IR组心律失常评分3.75±0.45相比,给药组(DH组2.25±1.18,DL组2.44±1.09)明显下降,心肌梗死面积明显缩小,心功能明显改善。结论薯蓣皂甙对大鼠心肌IR损伤具有保护作用。     

Renal ischemia/reperfusion remotely improves myocardial energy metabolism during myocardial ischemia via adenosine receptors in rabbits: effects of “remote preconditioning”

ObjectivesThis study examined the changes in myocardial energy metabolism during myocardial ischemia after “remote preconditioning” and investigated the involvement of adenosine receptors in the mechanisms of this effect.BackgroundRecent studies have indicated that a brief period of ischemia and reperfusion (ischemic preconditioning, PC) in a remote organ reduces myocardial infarct size (IS) protecting against subsequent sustained myocardial ischemia. However, the mechanisms of “remote PC” remain unclear. We assessed myocardial energy metabolism during sustained myocardial ischemia and reperfusion after renal PC (RPC), in comparison with that after myocardial PC (MPC) in open-chest rabbits. It has been established that adenosine receptors are involved in the mechanisms of MPC.MethodsRabbits that had been anesthetized with halothane were divided into six groups. The control (CNT) group underwent 40-min coronary occlusion followed by 120 min reperfusion. Before the procedure, the MPC group underwent an additional protocol of 5 min coronary artery occlusion and 20 min reperfusion, and the RPC group received a 10 min episode of renal artery occlusion and 20 min reperfusion. In additional experimental groups, 8 sulfophenyltheophylline (SPT, 10 mg/kg), an adenosine receptor inhibitor, was intravenously injected before the 40 min myocardial ischemia (SPT, MPC + SPT and RPC + SPT groups, respectively). Myocardial levels of phosphocreatine (PCr), ATP and intracellular pH (pHi) were measured by ³¹P-NMR spectroscopy.ResultsRPC and MPC delayed the decreases in ATP levels, preserved pHi during 40-min myocardial ischemia and resulted in better recovery of ATP and PCr during 120 min reperfusion compared with the controls. SPT abolished the improvement in myocardial energy metabolism and the reduction in myocardial IS caused by MPC or RPC. Myocardial IS in the CNT (n = 8), MPC (n = 9), RPC (n = 9), SPT (n = 6), MPC + SPT (n = 8) and RPC + SPT (n = 8) groups averaged 42.8 ± 3.5%, 18.2 ± 1.8%1, 19.6 ± 1.3%1, 44.9 ± 5.0%, 35.6 ± 2.7% and 34.8 ± 3.6% of the area at risk (1p < 0.05 vs. CNT), respectively.ConclusionsPC in a remote organ, similar to MPC, improved myocardial energy metabolism during ischemia and reperfusion and reduced IS in vivo by an adenosine-dependent mechanism in rabbits.     

Lack of Adenosine Causes Myocardial Refractoriness

Objectives. This study sought to investigate the myocardial mechanisms causing refractoriness to ischemic preconditioning in pigs.Background. Ischemic preconditioning in the pig vanishes after 60 min and cannot be reinstated by a second cycle of brief coronary occlusions at this time point. Ischemic preconditioning has been shown to be mediated by adenosine A₁-receptors. Because myocardial adenosine production during ischemia ceases as the number of repeated brief ischemic episodes increases, we hypothesized that this lack of adenosine may cause this myocardial refractoriness.Methods. In open chest pigs, ischemic preconditioning was achieved by repeated brief coronary occlusions. Myocardial adenosine content was assessed by high performance liquid chromatographic analysis of serial myocardial biopsy samples; infarct size (percent infarcted area of the area at risk) was determined using tetrazolium salts.Results. Ischemic preconditioning by two cycles of occlusion of the left anterior descending coronary artery (10 min) and reperfusion (30 min) decreased infarct size ([mean ± SEM] 40.4 ± 2.9%; control: 76.9 ± 1.8%, p < 0.001). Prolonging the second reperfusion period to 60 min caused ischemic preconditioning to vanish (79.0 ± 0.5%) and caused refractoriness to a second cycle of preconditioning (70.0 ± 2.0%). Myocardial adenosine content increased only during the first coronary occlusion (baseline: 110.9 ± 42.0 nmol/g dry weight; first coronary occlusion: 1,686.2 ± 244.1, p < 0.001) but not during subsequent coronary occlusions. In refractory myocardium, intramyocardial microinfusion of the adenosine A₁-receptor agonist N⁶-cyclohexyladenosine (CHA [0.3 mmol/liter]) again decreased infarct size (27.4 ± 7.0%, p < 0.001 vs. control).Conclusions. Myocardial refractoriness may be caused by the inability to produce adenosine endogenously. In refractory myocardium, application of CHA reinduces cardioprotection.     

Two-dimensional contrast echocardiographic assessment of the time course of regional ischemic myocardial function

The time course of percent fractional area change (%FAC) of the ischemic left ventricular wall as identified by myocardial contrast echocardiography was assessed. Two-dimensional echocardiograms of the left ventricular short axis at the level of the chordae tendineae were recorded in 16 anesthetized open-chest dogs. Myocardial ischemia was produced by occluding the left circumflex coronary artery (LCX) for 30 min, and identified by myocardial contrast echocardiography using aortic root contrast injection. The left ventricular wall in the short-axis view was divided into eight segments. The experiments were completed in nine dogs. The %FAC of the segment which includes the center of the ischemic area was normal before LCX occlusion (35 +/- 6%: mean +/- S.D.), markedly decreased during 30 min of LCX occlusion (-3 +/- 4%) and gradually recovered after coronary reperfusion. However, it was significantly decreased 150 min after reperfusion (8 +/- 9%) (p less than 0.001) compared to that before LCX occlusion. The %FAC of the segment which includes the center of the non-ischemic area was not significantly changed throughout the experiment. In conclusion, 1) the time course of regional ischemic myocardial function could be assessed by the analysis of the %FAC of the ischemic area determined by myocardial contrast echocardiography, 2) the %FAC is significantly decreased 150 min after coronary reperfusion following 30 min occlusion compared to that before coronary occlusion.     

Blockade of ATP-sensitive potassium channels prevents myocardial preconditioning in dogs.

Single or multiple brief periods of ischemia (preconditioning) have been shown to protect the myocardium from infarction after a subsequent more prolonged ischemic insult. To test the hypothesis that preconditioning is the result of opening ATP-sensitive potassium (KATP) channels, a selective KATP channel antagonist, glibenclamide, was administered before or immediately after preconditioning in barbital-anesthetized open-chest dogs subjected to 60 minutes of left circumflex coronary artery (LCX) occlusion followed by 5 hours of reperfusion. Preconditioning was elicited by 5 minutes of LCX occlusion followed by 10 minutes of reperfusion before the 60-minute occlusion period. Glibenclamide (0.3 mg/kg i.v.) or vehicle was given 10 minutes before the initial ischemic insult in each of four groups. In a fifth group, glibenclamide was administered immediately after preconditioning. In a final series (group 6), a selective potassium channel opener, RP 52891 (10 micrograms/kg bolus and 0.1 micrograms/mg/min i.v.) was started 10 minutes before occlusion and continued throughout reperfusion. Transmural myocardial blood flow was measured at 30 minutes of occlusion, and infarct size was determined by triphenyltetrazolium staining and expressed as a percent of the area at risk. There were no significant differences in hemodynamics, collateral blood flow, or area at risk between groups. The ratio of infarct size to area at risk in the control group (28 +/- 6%) was not different from the group pretreated with glibenclamide in the absence of preconditioning (31 +/- 6%). Preconditioning produced a marked reduction (p less than 0.002) in infarct size (28 +/- 6% to 6 +/- 2%), whereas glibenclamide administered before or immediately after preconditioning completely abolished the protective effect (28 +/- 6% and 30 +/- 8%, respectively). RP 52891 also produced a significant (p less than 0.03) reduction (28 +/- 6% to 13 +/- 3%) in infarct size. These results suggest that myocardial preconditioning in the canine heart is mediated by activation of KATP channels and that these channels may serve an endogenous myocardial protective role.     

Myocardial preconditioning and remote renal preconditioning

It is still unknown whether remote ischemic preconditioning is mediated by a humoral or a neurogenic mechanism from the preconditioning to the preconditioned tissue. The purpose of the following study was to identify a possible humoral trigger of ischemic myocardial preconditioning and remote renal preconditioning. Open chest rats were subjected to a coronary artery occlusion period of 45 min followed by 2 h of reperfusion (Control animals; n = 6). The coronary preconditioned group (IPC, n = 6) was subjected to a preceding preconditioning period of 5 min coronary artery occlusion followed by 5 min of reperfusion, repeated three times. The renal preconditioned group (IPR, n = 6) was subjected to a preceding renal artery occlusion period of 10 min followed by 20 min of reperfusion. Area at risk (AAR) and infarcted area (IA) were determined at the end of each protocol. Blood samples were taken at the end of the preconditioning protocols from parallel experiments for proteomic analysis using two–dimensional gel electrophoresis (2-DE), matrix assisted laser desorption and ionization—time of flight—mass spectrometry (MALDI–TOF–MS), and liquid chromatography—electrospray ionization—tandem mass spectrometry (nanoLC–ESI–MS/MS). IA/AAR was 87.8 ± 10.7% in the control group. IPC and IPR signi.cantly reduced IA/AAR (58.2 ± 9.3% and 56.9 ± 9.0%, p < 0.001). Proteomic analyses detected four protein spots which were either up– (n = 3) or down–regulated in the preconditioned groups vs. the control group. The three up–regulated protein spots were identi.ed as albumin fragments, whereas the downregulated spot was identified as liver regeneration–related protein (LRRG03). Interestingly, albumin modification by brief ischemia has been recently shown and evaluated for the clinical diagnosis of sublethal myocardial ischemia. However, no differentially abundant proteins which possess a known signaling function could be found. Hence, though there is a differential protein expression in blood following IPC and IPR, our data are not in favor of a humoral mediator of remote preconditioning with a molecular weight of more than 8 kDa. Our results rather suggest either a neurogenic pathway or a mediator smaller than 8 kDa.     

Regional differences in postischemic recovery in the stunned canine myocardium

To determine if differences exist in the degree of ischemic damage and in postischemic recovery when different coronary arteries are occluded and reperfused, 40 barbital-anesthetized dogs were subjected to brief 15-minute periods of coronary artery occlusion followed by 3 hours of reperfusion ("stunned" myocardium) of the left anterior descending (LAD) or the left circumflex (LCX) coronary arteries. Myocardial segment shortening (%SS) in the subendocardium of nonischemic and ischemic reperfused areas was measured by sonomicrometry, and regional myocardial blood flow was measured by radioactive microspheres. Transmural tissue biopsies were taken at the end of reperfusion for the measurement of adenine nucleotides and total tissue water content. Arterial and local coronary venous blood samples were collected during preocclusion, during occlusion, and at 30 and 180 minutes of reperfusion for determination of blood oxygen content and oxygen consumption in the ischemic area. During occlusion, subendocardial blood flow (LAD flow = 0.11 +/- 0.02; LCX flow = 0.15 +/- 0.04 ml/min/gm), myocardial oxygen consumption (LAD = 2.4 +/- 0.7; LCX = 2.7 +/- 0.7 ml/min/100 gm), and areas of the left ventricle at risk (LAD = 27.4 +/- 2.3%; LCX = 32.4 +/- 2.4) were similar in both groups, thus indicating equivalent degrees of ischemia. There were no differences between groups in hemodynamics throughout the experiment or in the loss of myocardial high-energy phosphates or increase in total tissue water in the ischemic reperfused area at 3 hours of reperfusion. There was a significantly greater loss (p less than 0.05) of systolic wall function during LAD versus LCX occlusion and a greater recovery of segment function from 5 minutes throughout 1 hour of reperfusion after LCX occlusion (p less than 0.05), with no difference in %SS at 2 and 3 hours following reperfusion. Thus, although similar changes occurred in blood flow, metabolite parameters, tissue edema, wall function, and overall hemodynamics when either the LAD or LCX perfusion territories were occluded and reperfused, the loss of systolic wall function and recovery of segment shortening were more variable after regional stunning of the LCX perfusion bed. These data suggest that evaluation of pharmacologic or surgical interventions to improve postischemic functional recovery may be more reliably performed when the LAD coronary artery is the vessel occluded.     

Angiotensin II Receptor Antagonist EXP 3174 Reduces Infarct Size Comparable with Enalaprilat and Augments Preconditioning in the Pig Heart

There is no agreement on the effect of angiotensin II receptor blockade in the setting of ischemic reperfusion. Our aim was to assess the acute effects of angiotensin-converting enzyme (ACE) inhibition and angiotensin II AT1-subtype receptor blockade in pig heart. Five groups of open-chest pigs received 1 hour of left anterior descending (LAD) coronary artery occlusion and 2 hours of reperfusion. Left ventricular pressure was monitored by an intraventricular catheter, and regional segment shortening (%SS) in the LAD-supplied territory was measured by ultrasonic crystals implanted in the subendocardium. Group 1 (n = 6) served as the control; groups 2 (n = 6) and 3 (n = 6) received the angiotensin II receptor blocker, EXP 3174 (C₂₂H₂₁Cl₁ N₆O₂), and the ACE inhibitor, enalaprilat, respectively, prior to LAD occlusion; group 4 (n = 6) was preconditioned with two cycles of 10 minutes of coronary occlusion and 30 minutes of reperfusion; and group 5 (n = 6) underwent preconditioning with additional administration of EXP 3174 prior to the 60-minute occlusion period. Infarct sizes were measured by p-nitrobluetetrazolium staining and were expressed in percent of the ischemic area of risk. The angiotensin II receptor blocker EXP 3174 and enalaprilat reduced infarct sizes significantly (35.3 ± 17.1% and 40.1 ± 15.1%, respectively) compared with controls (71.2± 12.8%, P < 0.05), and EXP 3174 augmented the infarct size–limiting effects of preconditioning by ischemia (10.5 ± 6% vs. 28.6 ± 5.3%, P < 0.05). Regional contractile dysfunction during reperfusion demonstrated no changes after angiotensin II receptor blockade. Angiotensin II receptor blockade reduced infarct size comparable with that obtained with angiotensin converting-enzyme inhibition. The infarct size–limiting effects of ischemic preconditioning were augmented by administration of the angiotensin II receptor antagonist EXP3174. These data support the concept that blockade or inhibition of angiotensin II before coronary occlusion is protective in a swine model of acute ischemia and reperfusion. This revised version was published online in July 2006 with corrections to the Cover Date.     

缺血预适应减少缺血再灌注冠状窦血浆内皮素的含量

目的:观察缺血预适应(PC)对缺血再灌注(IR)后冠状窦血浆内皮素(ET)含量的影响。方法:以单纯的心肌缺血(阻闭家免冠脉左前降支近端)30min+再灌注30min为对照,观察经PC(缺血5min+再灌注10min)后IR心肌的梗死范围、超微结构以及室颤(VF)或室速(VT)的发生率,并采用均相放射免疫竞争法,测量比较两组1R后冠状窦血浆ET含量。结果:PC后心肌梗死范围缩小约60％、VF／VT的发生率降低(P<0.05);电镜下,心肌细胞的损伤减轻;血浆ET含量明显减少(P<0.01)。结论:PC减少IR时冠脉ET的分泌,可能是PC保护心肌组织结构及抗IR心律失常的部分病理生理机制。     

ISCHEMIC PRECONDITIONING AND INFARCT MASS: THE EFFECT OF HYPERCHOLESTEROLEMIA AND ENDOTHELIAL DYSFUNCTION

In an experimental model of atherosclerosis we investigated whether rabbits fed an atherogenic diet (0.25% cholesterol, 3% coconut oil) develop endothelial dysfunction accompanied with increased infarct mass compared to normal fed rabbits and, whether hypercholesterolemia would interfere with the beneficial outcome of ischemic preconditioning observed in normal rabbits. After four weeks on either a normal or an atherogenic diet, New Zealand White rabbits (n=7 in each group) were subjected to 30 min of myocardial ischemia by occlusion of a branch of the left anterior descending coronary artery (LAD) followed by 2 hours of reperfusion (infarct studies). For ischemic preconditioning experiments, LAD was additionally occluded twice for 5 min followed by 10 min reperfusion before the long-lasting (30 min) ischemia. Infarct mass was evaluated by triphenyl-tetrazolium staining. Besides the assessment of aortic endothelium-dependent function and NO-release, aortic and cardiac vessels were inspected for atherosclerotic lesions. Total cholesterol serum levels in rabbits on an atherogenic diet were significantly higher (15.3±2.7 mmol/L) than those on a standard diet (0.65±0.08 mmol/L). The aortas and heart vessels were without any histological evidence of atherosclerosis, whereas endothelial dysfunction and significantly reduced calcium-ionophore stimulated endothelial NO-release were found in isolated aortic rings of hypercholesterolemic animals. Rabbits on a standard diet showed an infarct mass (related to the area at risk) of 41±3%, which was reduced to 21±2% by ischemic preconditioning (49% decrease, p<05). In rabbits on an atherogenic diet, infarct mass was significantly increased to 63±3% (52% increase versus standard diet). Interestingly, hypercholesterolemia did not affect the beneficial influence of ischemic preconditioning; infarct mass (21±3%, p<0.05 vs hypercholesterolemia) was similar to rabbits on a standard diet with ischemic preconditioning.

Our results show that experimental hypercholesterolemia increases infarct mass in nonpreconditioned hearts but it does not interfere with the reduction of infarct mass elicited by preconditioning. This may suggest that NO produced by the endothelium is not a prime factor in the cardioprotective mechanism of preconditioning.