烟碱预先给药对心肌缺血再灌注大鼠心功能的影响

目的 评价烟碱预先给药对心肌缺血再灌注大鼠心功能的影响.方法 健康成年雄性SD大鼠60只,体重200 ～ 250 g,采用随机数字表法,将其分为3组(n=20)∶假手术组(S组)、心肌缺血再灌注组(IR组)和烟碱预先给药组(N组).S组丝线穿过冠状动脉前降支但不结扎；IR组采用丝线结扎左冠状动脉前降支30 min后再灌注120 min的方法制备大鼠心肌缺血再灌注模型.N组结扎前30 min,经右颈静脉注射烟碱400μg/kg,余操作同IR组,S组和IR组右颈静脉注射等量生理盐水.各组随机取10只大鼠于缺血前(T0)、缺血30 min(T1)和再灌注30 min(T2)、120 min(T3)时经生物机能实验系统记录左心室收缩压(LVSP)、左心室舒张压(LVDP)、左室内压上升/下降最大变化速率(±dp/dtmax)、HR和MAP.各组其余10只大鼠于再灌注60 min时采集右颈动脉血样,采用ELISA法测定血浆肌酸激酶同工酶(CK-MB)活性、心肌肌钙蛋白I(cTnI)和TNF-α浓度.结果 与S组比较,IR组T23时MAP和LVSP、T13时HR、LVDP和±dp/dtmax降低,血浆CK-MB活性、cTnI和TNF-α浓度升高,N组T1-2时LVDP、T1-3时HR和±dp/dtmax降低,血浆CK-MB活性、cTnI和TNF-α浓度升高(P＜0.05)；与IR组比较,N组T3时MAP、HR、LVSP、LVDP和±dp/dtmax升高,血浆CK-MB活性、cTnI和TNF-α浓度降低(P＜0.05).结论 烟碱预先给药通过激活胆碱能抗炎通路,抑制炎性反应,可显著减轻大鼠心肌缺血再灌注损伤,从而改善心功能.     

七氟醚预处理对大鼠心肌缺血再灌注时缝隙连接蛋白43的影响

目的 评价七氟醚预处理对大鼠心肌缺血再灌注时缝隙连接蛋白43的影响.方法 健康成年雄性Wistar大鼠,体重220 ～ 250 g,采用改良Langendorff灌注装置制备离体心脏灌注模型.取离体心脏模型16个,采用随机数字表法,将其随机分为2组(n=8):缺血再灌注组(I/R组)和七氟醚预处理组(SP组).平衡灌注30 min时,I/R组继续灌注K-H液20 min;SP组将2.4％七氟醚持续吹入K-H液中,用预充2.4％七氟醚的K-H液持续灌注15 min,然后用K-H液洗脱5 min.之后两组均行全心缺血40 min,再灌注60 min.分别于平衡灌注末、缺血前即刻、再灌注30和60 min时,记录HR、左室发展压(LVDP)、左心室内压最大上升速率(+dp/dtmax)及左心室内压最大下降速率(- dp/dtmax).于再灌注60 min时,取部分心尖组织,观察心肌病理学改变;取左室部分心肌,观察缝隙连接蛋白43的分布情况,测定缝隙连接蛋白43的表达.结果 与平衡灌注末比较,I/R组和SP组缺血前即刻+ dp/dtmax和- dp/dtmax降低,再灌注30和60 min时HR、LVDP、+dp/dtmax和- dp/dtmax降低(P＜0.01);与缺血前即刻比较,I/R组和SP组再灌注30和60 min时HR、LVDP、+dp/dtmax和- dp/dtmax降低(P ＜0.05或0.01);与I/R组比较,SP组缺血前即刻HR、LVDP、+dp/dtmax和- dp/dtmax降低,再灌注30和60 min时HR、LVDP、+dp/dtmax和- dp/dtmax升高(P＜0.01),病理学损伤减轻.缝隙连接蛋白43 I/R组分布不均,闰盘处少见;SP组分布规律呈条带状,主要位于闰盘处.两组缝隙连接蛋白43表达比较差异无统计学意义(P＞0.05).结论 七氟醚预处理减轻大鼠心肌缺血再灌注损伤的机制可能与抑制缝隙连接蛋白43的再分布有关,而与缝隙连接蛋白43的表达无关.     

依达拉奉后处理联合远隔缺血后处理对大鼠心肌缺血再灌注损伤的影响

目的 评价依达拉奉后处理联合远隔缺血后处理对大鼠心肌缺血再灌注损伤的影响.方法 健康雄性SD大鼠40只,8周龄,体重250～300 g,采用随机数字表法,将其分为5组(n=8):假手术组(S组)、缺血再灌注组(I/R组)、依达拉奉后处理组(E组)、远隔缺血后处理组(P组)、依达拉奉联合远隔缺血后处理组(EP组).采用结扎左冠状动脉前降支30 min,再灌注180 min制备心肌缺血再灌注模型.E组和EP组再灌注前1 min静脉注射依达拉奉3mg/kg;P组和EP组左冠状动脉结扎20 min时实施远隔后处理:用止血带结扎大鼠双后肢,持续10 min.于心肌缺血再灌注期间记录左心室峰压(LVSP)、左心室舒张末压(LVEDP)、左室内压最大上升速率(+dp/dtmax)、左室内压最大下降速率(-dp/dtmax).结果 与S组比较,其它各组再灌注期间LVSP、+dp/dtmax、-dp/dtmax降低,LVEDP升高(P＜0.05);与I/R组比较,E组、P组及EP组再灌注期间LVSP、+dp/dtmax、-dp/dtmax升高,LVEDP降低(P＜0.05);与E组和P组比较,EP组再灌注期间LVSP、+dp/dtmax、-dp/dtmax升高,LVEDP降低(P＜0.05).结论 依达拉奉后处理联合远隔缺血后处理可减轻心肌缺血再灌注损伤,且效果强于两者单独应用.     

异丙酚预先给药对糖尿病大鼠心肌缺血再灌注损伤的影响

目的 探讨异丙酚预先给药对糖尿病大鼠心肌缺血再灌注损伤的影响.方法 健康雄性SD大鼠84只,体重230～280 g,随机分为7组(n=12),假手术组(Ⅰ组);Ⅱ组采用结扎左冠状动脉前降支30 min,再灌注120 min制备心肌缺血再灌注模型;糖尿病大鼠假手术组(Ⅲ组)采用腹腔注射链脲左菌素(STZ)55 mg/kg制备糖尿病模型;糖尿病大鼠心肌缺血再灌注组(Ⅳ组)腹腔注射STZ 3周后制备心肌缺血再灌注模型;Ⅴ组、Ⅵ组和Ⅶ组糖尿病大鼠分别于缺血前10 min至再灌注120 min时静脉输注异丙酚3、6、12 mg·kg-1·h-1.记录再灌注120 min时心率(HR)、左心室收缩峰压、左心室舒张末压(LVDEP)及左心室内压上升,下降最大速率(±dp/dtmax),计算左心室发展压(LVDP);测定血清肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH)活性、心肌组织超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量、心肌线粒体肿胀度、总ATP酶和谷胱苷肽过氧化物酶(GSH-Px)活性;透射电镜观察心肌组织超微结构.结果 与Ⅲ组比较,Ⅳ组HR、LVDP和±dp/dtmax、心肌组织SOD活性、线粒体总ATP酶及GSH-Px活性降低,LVEDP、血清LDH、CK-MB活性、心肌组织MDA含量及线粒体肿胀度升高(P<0.05或0.01);与Ⅳ组比较,Ⅵ组和Ⅶ组HR、LVDP和±dp/dtmax、心肌组织SOD活性、线粒体总ATP酶及GSH-Px活性升高,LVEDP、血清LDH、CK-MB活性、心肌组织MDA含量和线粒体肿胀度降低,Ⅴ组+dp/dtmax及线粒体总ATP酶活性升高,血清CK-MB活性降低(P<0.05).Ⅵ组和Ⅷ组心肌组织超微结构损伤减轻.结论 异丙酚6、12 mg·kg-1·h-1预先给药可减轻糖尿病大鼠心肌缺血再灌注损伤,可能与其抑制心肌组织脂质过氧化反应,改善心肌细胞线粒体膜通透性有关.     

3-硝基丙酸化学预处理对大鼠离体心脏缺血-再灌注损伤的影响

目的研究3-硝基丙酸(3-NPA)化学预处理对大鼠离体心脏缺血-再灌注损伤的保护作用及其机制。方法16只Wistar大鼠随机分为2组,每组8只。实验组(3-NPA组):腹腔注射3-NPAmg·kg-1预处理24h;对照组(C组):腹腔注射等体积生理盐水。采用Langendorff离体心脏灌流模型,两组行常温缺血30min-再灌注60min模拟心肌缺血-再灌注损伤。观察各组缺血前(基础值)和再灌注后30、60min时心率(HR)、左心室发展压(LVDP)、左心室压力上升和下降最大变化速率(±dp/dtmax),测定再灌注后15min时冠脉流出液肌酸激酶(CK)和乳酸脱氢(LDH)活性,测定再灌注后60min时心肌丙二醛(MDA)含量和超氧化物岐化酶(SOD)活性。结果与C组比较,3-NPA组LVDP、 dp/dtmax再灌注后30、60min、-dp/dtmax再灌注后60min时升高(P<0.01或0.05),HR组间比较差异无统计学意义(P>0.05),灌注后15min时冠脉流出液CK和LDH活性降低,再灌注后60min时心肌SOD活性明显升高,心肌MDA含量降低。结论4mg·kg-13-NPA预处理对大鼠离体心脏缺血-再灌注损伤具有一定的保护作用,其机制可能是减少氧自由基的产生和提高SOD活性。     

吡那地尔超极化停搏对大鼠离体心脏蛋白激酶C及热休克蛋白70的影响

目的探讨吡那地尔超极化停搏对大鼠离体心脏蛋白激酶C（PKC）ε及热休克蛋白70 （HSP70）的影响。方法成年雄性SD大鼠,成功建立Langendorff离体再灌注模型的32个心脏,随机分为4组（n=8）：自然停搏组（A组）、St.Thomas组（B组）、吡那地尔超极化组（C组）和白屈菜赤碱组（D组）。A组、B组和C组K-H液平衡灌注15min后,A组停止灌注,B组灌注St.Thomas停搏液,C组灌注超极化停搏液;D组K-H液平衡灌注10min后,白屈菜赤碱液灌注5min,再灌注超极化停搏液。记录各组平衡灌注15min和再灌注20min时冠脉流量（CF）、心率（HR）、左室发展压（LVDP）、左室收缩峰压（LVSP）和左室压力瞬时最大变化率（dp/dtmax）;再灌注30min时测定心肌膜性PKCε和HSP70的表达。结果与K-H液平衡灌注15min时相比,再灌注20min时A组、B组和D组CF、HR、LVSP、LVDP及dp/dtmax降低（P〈0.05）;与C组相比,其余各组再灌注20min时CF、HR、LVSP、LVDP及dp/dtmax降低,膜性PKCε和HSP70的表达下调（P〈0.05）。结论吡那地尔超极化停搏通过上调膜性PKCε和HSP70表达,促进大鼠心肌缺血再灌注时心功能恢复。     

右美托咪定预处理对大鼠心肌缺血-再灌注后心室功能和细胞凋亡的影响

目的探讨右美托咪定预处理对大鼠心肌缺血-再灌注损伤后心室功能和心肌细胞凋亡的影响。方法 30只SD大鼠随机分为三组,右美托咪定组(D组),右美托咪定+育亨宾组(D+Y组)和对照组(IR组),D组给予右美托咪定5μg·kg-1·h-1预处理1h,D+Y组静脉注射育亨宾1mg/kg,10min后按5μg·kg-1·h-1输注右美托咪定1h;IR组仅输注等量生理盐水,建立Langendorff缺血-再灌注模型,每10分钟测定左心室舒张末压(LVEDP)、左心室收缩压(LVSP)、左心室内压最大上升速率、下降速率(±dp/dtmax),计算左心室发展压(LVDP)。60min后取下心脏并以TUNEL检测心肌细胞的凋亡,RT-PCR检测Bcl-2mRNA,Bax mRNA的表达。结果与D组比较,再灌注后不同时点IR组和D+Y组大鼠LVDP、±dp/dtmax、Bcl-2mRNA表达明显降低、LVEDP、Bax mRNA表达明显升高(P0.05)。IR组和D+Y组LVDP、LVEDP、±dp/dtmax、Bcl-2mRNA和Bax mRNA表达差异均无统计学意义。IR组细胞阳性率为(36.1±9.2)%、D+Y组为(38.2±6.5)%,明显高于D组为(24.0±8.3)%(P0.05),而IR组和D+Y组细胞阳性率差异无统计学意义。结论右美托咪定预处理可以显著改善大鼠心肌缺血-再灌注损伤后的心室功能,并且可能通过调控凋亡基因Bcl-2mRNA和促凋亡基因BaxmRNA的表达,减少心肌细胞凋亡。     

舒芬太尼后处理和七氟醚后处理对大鼠离体心脏缺血再灌注损伤的影响

目的 评价舒芬太尼后处理和七氟醚后处理对大鼠离体心脏缺血再灌注损伤的影响.方法 雄性SD大鼠,体重230～250 g,成功制备Langendorff离体灌注模型的40个心脏随机分为4组(n=10):缺血再灌注组(Ⅰ组)、七氟醚后处理组(Ⅱ组)、舒芬太尼后处理组(Ⅲ组)和七氟醚联合舒芬太尼后处理组(Ⅳ组).采用K-H液平衡灌注(灌注压10 kPa)30 min,全心缺血40 min再灌注120 min.再灌注即刻时Ⅱ组、Ⅲ组和Ⅳ组进行药物后处理15 min:Ⅱ组K-H液中通入3.0%七氟醚,Ⅲ组K-H液中加入100 nmol/L舒芬太尼,Ⅳ组同时进行七氟醚后处理和舒芬太尼后处理.分别于平衡灌注末(基础状态)、再灌注15 min、30 min、60 min、90 min、120 min时记录左室收缩压(LVSP)、左室舒张末压(LVEDP)、左室发展压(LVDP)、左室内压上升最大速率(+dp/dtmax)、左室内压下降最大速率(-dp/dtmax)、心率(HR)和灌脉流量(CF).再灌注5 min时,收集冠脉流出液,测定肌酸激酶(CK)和乳酸脱氢酶(LDH)的活性.再灌注120 min时取心肌组织,测定心肌梗死体积、Bcl-2和Bax的表达水平,并计算Bcl-2和Bax表达的比值(Bcl-2/Bax).结果 与Ⅰ组比较,Ⅱ组、Ⅲ组和Ⅳ组LVSP、LVDP、+dp/dtmax、-dp/dtmax和CF升高,LVEDP和LDH、CK的活性降低,心肌梗死体积缩小,Bcl-2表达上调,Bax表达下调,Bcl-2/Bax升高(P＜0.05或0.01);Ⅱ组、Ⅲ组和Ⅳ组间上述指标差异无统计学意义(P＞0.05).结论 舒芬太尼后处理可减轻大鼠心肌缺血再灌注损伤,联合七氟醚后处理时心肌保护作用并未增加,其心肌保护的机制与上调Bcl-2表达、下调Bax表达从而抑制细胞凋亡有关.     

大鼠离体心脏心肌胰岛素抵抗实验模型的建立

目的建立大鼠离体心脏缺血再灌注实验模型并明确其诱导心肌胰岛素抵抗的效果。方法 12只雄性Sprague-Dawley(SD)大鼠由贵州医科大学实验动物中心提供, 按随机数字表法分为两组, 正常对照(NC)组(6例)离体心脏持续灌注60 min, 缺血再灌注(I/R)组(6例)全心缺血30 min, 再灌注30 min, 记录心功能指标, 检测肌酸激酶MB同工酶(CK-MB)和心肌肌钙蛋白T(cTnT)含量, 苏木精-伊红染色观察心肌组织细胞形态, 蛋白质免疫印迹和组织免疫荧光检测葡萄糖转运蛋白4(GLUT4)的表达和转位情况。组间比较用独立样本t检验。结果 I/R组心功能指标[左心室发展压(LVDP)(50.8±5.5) mmHg(1 mmHg=0.133 kPa)、左心室内压最大上升速率(+dp/dtmax)(2 566.6±358.6) mmHg/s、左心室内压最大下降速率(-dp/dtmax)(1 172.6±121.2) mmHg/s]明显低于NC组[LVDP(79.9±4.0) mmHg、+dp/dtmax(3 587.8±334.5) mmHg/s、-dp/dtmax(2 ...     

心肌细胞缝隙连接蛋白43在线粒体敏感性钾通道介导七氟醚预处理减轻大鼠离体心脏缺血再灌注中的作用

目的 评价心肌细胞缝隙连接蛋白43(Cx43)在线粒体敏感性钾(mito-KATP)通道介导七氟醚预处理减轻大鼠离体心脏缺血再灌注中的作用.方法 健康成年雄性SD大鼠40只,体重200～250 g,采用Langendorff灌注模型进行离体心脏灌注.采用随机数字表法,将心脏随机分为5组(n=8):对照组(C组)、缺血再灌注组(I/R组)、七氟醚预处理组(S组)、七氟醚预处理+5-羟葵酸(5-HD)组(SH组)和5-HD组(H组).采用结扎左冠状动脉前降支(LAD) 30 min,恢复灌注120 min的方法制备心脏缺血再灌注模型.各组平衡灌注10 min;然后C组持续灌注,仅于LAD下穿线而不结扎;I/R组继续灌注30 min后结扎LAD;S组、S+H组和H组结扎LAD前30 min时分别用3％七氟醚预先饱和的K-H液、3％七氟醚预先饱和的K-H液+100 μmol/L 5-HD和K-H液+100 μmol/L 5-HD灌注15 min,然后用K-H液冲洗15 min.分别于给药前(T0)、给药结束即刻(T1)、缺血前即刻(T2)、缺血30 min(T3)和再灌注120 min(T4)时,记录HR、左心室收缩压(LVSP)、左心室舒张压(LVDP)、左心室最大上升速率(+dp/dtmax)和左心室最大下降速率(- dp/dtmax).再灌注结束后,取左心室心肌组织,测定心肌梗死体积,采用免疫组化法测定心肌细胞Cx43表达,采用Western Blot法测定心肌细胞Cx43和磷酸化Cx43(p-Cx43)表达.结果 与C组比较,I/R组、S+H组和H组HR、LVSP、+dp/dtmax和- dp/dtmax降低,LVDP升高,心肌细胞Cx43和p-Cx43表达下调(P＜0.05).与I/R组比较,S组HR、LVSP、+dp/dtmax和- dp/dtmax升高,LVDP和心肌梗死体积降低,心肌细胞Cx43和p-Cx43表达上调(P＜0.05),S+H组和H组各指标差异无统计学意义(P＞0.05).结论 七氟醚预处理可能通过开放mito-KATP通道,促进心肌细胞Cx43磷酸化,减轻大鼠离体心脏缺血再灌注损伤.     

Sialyl LewisX oligosaccharide preserves myocardial and endothelial function during cardioplegic ischemia

BACKGROUND: Neutrophil adhesion to endothelium contributes to myocardial reperfusion injury after cardiac operation. Initial neutrophil-endothelial interactions involve selectins, which bind Sialyl-LewisX on neutrophils. Blockade of selectin-mediated neutrophil-endothelial interactions with CY-1503, a synthetic analogue of Sialyl-LewisX, might reduce reperfusion injury after myocardial ischemia. METHODS: The efficacy of CY-1503 to attenuate global myocardial reperfusion injury was assessed in isolated blood-perfused neonatal lamb hearts that had 2 hours of cold cardioplegic ischemia. CY-1503 (40 mg/L) or saline vehicle was added to blood perfusate before ischemia. Contractile function (developed pressure, dP/dt) and coronary vascular endothelial function (acetylcholine response) were assessed at base line and during reperfusion. Myocardial neutrophil accumulation was assessed by myeloperoxidase quantification. RESULTS: Compared to controls, treatment with CY-1503 improved recovery of all indices of contractile function, preserved coronary vascular endothelial function, and reduced myocardial neutrophil accumulation. CONCLUSIONS: In isolated neonatal lamb hearts that underwent hypothermic cardioplegic ischemia, CY-1503 administration reduced myocardial neutrophil accumulation and preserved endothelial and contractile function. Selectin blockade of leukocyte-endothelial interactions might attenuate reperfusion injury and enhance myocardial protection during cardiac surgical procedures.     

Sevoflurane before or after Ischemia Improves Contractile and Metabolic Function while Reducing Myoplasmic Ca2+ Loading in Intact Hearts

Background: Ca2+ loading occurs during myocardial reperfusion injury. Volatile anesthetics can reduce reperfusion injury. The authors tested whether sevoflurane administered before index ischemia in isolated hearts reduces myoplasmic diastolic and systolic [Ca2+] and improves function more so than when sevoflurane is administered on reperfusion.

Methods: Four groups of guinea pig hearts were perfused with crystalloid solution (55 mmHg, 37[degrees]C): (1) no treatment before 30 min global ischemia and 60 min reperfusion (CON); (2) 3.5 vol% sevoflurane administered for 10 min before ischemia (SBI); (3) 3.5 vol% sevoflurane administered for 10 min after ischemia (SAI); and (4) 3.5 vol% sevoflurane administered for 10 min before and after ischemia (SBAI). Phasic myoplasmic diastolic and systolic [Ca2+] were measured in the left ventricular free wall with the fluorescence probe indo-1.

Results: Ischemia increased diastolic [Ca2+] and diastolic left ventricular pressure (LVP). In CON hearts, initial reperfusion greatly increased diastolic [Ca2+] and systolic [Ca2+] and reduced contractility (systolic-diastolic LVP, dLVP/dtmax), relaxation (diastolic LVP, dLVP/dtmin), myocardial oxygen consumption (Mvo2), and cardiac efficiency. SBI, SAI, and SBAI each reduced ventricular fibrillation, attenuated increases in systolic and systolic-diastolic [Ca2+], improved contractile and relaxation indices, and increased coronary flow, percent oxygen extraction, Mvo2, and cardiac efficiency during 60 min reperfusion compared with CON. SBI was more protective than SAI, and SBAI was generally more protective than SAI.     

吗啡预处理-后处理对大鼠离体心脏缺血再灌注损伤的影响

目的 探讨吗啡预处理-后处理对大鼠离体心脏缺血再灌注损伤的影响.方法 雄性SD大鼠,体重180～200 g,应用Langendorff体外灌流装置,采用全心停灌45 min、再灌注60 min的方法制备大鼠离体心脏缺血再灌注模型.取模型制备成功的心脏40个,随机分为5组(n=8):缺血再灌注组(IR组)、吗啡预处理组(M1组)、吗啡后处理组(M2组)、吗啡预处理-后处理组(M1+M2组)、5-羟葵酸(5-HD)混合吗啡后处理组(5-HD+M2组).M1组全心停灌前30 min灌注含3.0 μmol/L吗啡的K-H液20 min,随后灌注K-H液10 min.M2组再灌注即刻灌注含3.0 μmol/L吗啡的K-H液10 min,随后灌注正常K-H液50 min.5-HD+M1组再灌注即刻灌注含3.0 μmol/L吗啡+10-4nunol/L 5-HD的K-H液10 min,随后灌注正常K-H液50 min.于再灌注60 min时,测定心肌肌酸激酶(CK-MB)活性,计算心肌梗死区与缺血危险区的比值(IS/AAR).结果 与IR组相比,其余各组IS/AAR减少,CK-MB活性降低(P<0.05);与M2组比较,5-HD+M2组CK-MB活性及IS/AAR升高(P<0.05);M1组、M2组和M1+M2组上述指标比较差异无统计学意义(P>0.05).结论 吗啡预处理.后处理虽然可减轻大鼠离体心脏缺血冉灌注损伤,但是与单独应用时效果相似,其原因可能是两者单独应用减轻心脏缺血再灌注损伤的机制均与开放线粒体ATP敏感性钾通道有关.     

Sevoflurane before or after ischemia improves contractile and metabolic function while reducing myoplasmic Ca(2+) loading in intact hearts.

BACKGROUND: Ca(2+) loading occurs during myocardial reperfusion injury. Volatile anesthetics can reduce reperfusion injury. The authors tested whether sevoflurane administered before index ischemia in isolated hearts reduces myoplasmic diastolic and systolic [Ca(2+)] and improves function more so than when sevoflurane is administered on reperfusion. METHODS: Four groups of guinea pig hearts were perfused with crystalloid solution (55 mmHg, 37 degrees C): (1) no treatment before 30 min global ischemia and 60 min reperfusion (CON); (2) 3.5 vol% sevoflurane administered for 10 min before ischemia (SBI); (3) 3.5 vol% sevoflurane administered for 10 min after ischemia (SAI); and (4) 3.5 vol% sevoflurane administered for 10 min before and after ischemia (SBAI). Phasic myoplasmic diastolic and systolic [Ca(2+)] were measured in the left ventricular free wall with the fluorescence probe indo-1. RESULTS: Ischemia increased diastolic [Ca(2+)] and diastolic left ventricular pressure (LVP). In CON hearts, initial reperfusion greatly increased diastolic [Ca2+] and systolic [Ca(2+)] and reduced contractility (systolic-diastolic LVP, dLVP/dt(max)), relaxation (diastolic LVP, dLVP/dt(min)), myocardial oxygen consumption (MvO(2)), and cardiac efficiency. SBI, SAI, and SBAI each reduced ventricular fibrillation, attenuated increases in systolic and systolic-diastolic [Ca(2+)], improved contractile and relaxation indices, and increased coronary flow, percent oxygen extraction, MvO(2), and cardiac efficiency during 60 min reperfusion compared with CON. SBI was more protective than SAI, and SBAI was generally more protective than SAI. CONCLUSIONS: Sevoflurane improves postischemic cardiac function while reducing Ca(2+) loading when it is administered before or after ischemia, but protection is better when it is administered before ischemia. Reduced Ca(2+) loading on reperfusion is likely a result of the anesthetic protective effect.     

Increasing heart size and age attenuate anesthetic preconditioning in guinea pig isolated hearts

Anesthetic preconditioning (APC) reduces myocardial ischemia/reperfusion injury. Recent investigations have reported that older hearts are not susceptible to APC. We investigated if increasing heart size with age determines the susceptibility to APC in young guinea pigs. Langendorff-prepared guinea pig hearts of different weights (1.1-2.2 g) and ages (2-7 wks) were exposed to 1.3 mM sevoflurane for 15 min followed by 30 min washout (APC; n = 20) before 30 min global ischemia and 120 min reperfusion. Control hearts (n = 20) were not subject to APC. Left ventricular pressure was measured isovolumetrically and infarct size was determined by triphenyltetrazolium staining. Functional data were not different between groups at the beginning of the experiments nor did they correlate with heart weight or age. At 120 min reperfusion, left ventricular pressure, coronary flow, and tissue viability showed significant negative correlations with increasing heart weight and age in APC but not in control hearts; i.e., APC improved function and attenuated infarct size better in smaller/younger hearts than in larger/older hearts. Thus, increasing age and heart size attenuate the susceptibility for APC even in younger guinea pigs. This may have important implications for further basic science research and the possible clinical applicability of APC in humans.     

Ultrastructural changes in rat hearts following cold cardioplegic ischemia of differing duration and differing modes of reperfusion

Morphologic consequences of prolonged global hypothermic (15 degrees C), cardioplegic ischemia and two reperfusion techniques were studied in Langendorff-perfused rat hearts. A 'gentle' reperfusion technique, with gradual rise in perfusate temperature and pressure to physiologic levels over 30 min, was used for 12 hearts following 2-hour or 3 1/2-hour (6 in each group) ischemia. Abrupt reperfusion, with perfusate at 37 degrees C and 70 mmHg, was performed on 13 hearts (6 ischemic for 2 hours and 7 for 3 1/2 hours). Six nonischemic, perfused hearts served as controls. Randomly selected specimens from the left ventricle after 45-60 min reperfusion were prepared for transmission electron microscopy. Volume fractions of myocardial structural components were calculated from stereologic point-counting on the electron micrographs. Two-way analysis of variance revealed that interstitial edema developed with increasing ischemic time and was not influenced by reperfusion technique. The degree of endothelial damage was independent of ischemic time, but was lessened by 'gentle' reperfusion. Both mitochondrial injury and myocyte edema were less when perfusate temperature and pressure were slowly raised after 3 1/2-hour ischemia.     

2-Nicotinamidoethyl nitrale (2-NN) protects myocardium in ischemia and reperfusion via the protein kinase C pathway

BACKGROUND: Several recent studies have suggested an ATP-sensitive potassium channel opener (2-nicotinamidoethyl nitrate: 2-NN) may exert a protective effect against the myocardial ischemic/reperfusion injury. This study examines the effects of 2-NN on intracellular signaling by measuring intracellular cyclic AMP, cyclic GMP accumulation and protein kinase C (PKC) activity after 2-NN perfusion. METHODS: Ischemia/reperfused hearts were made by LAD occlusion for 30 min followed by 30 min of reperfusion in isolated rat hearts. Hearts were pre-perfused with 0.1 mM 2-NN, 100 nM Calphostin C, or 2-NN plus Calphostin C for 10 min prior to ischemia. The left ventricular function, cyclic AMP, cyclic GMP and LDH were examined to determine the effects of 2-NN on ischemic/reperfusion injury. Four separate groups of hearts were stained with a bisindolylmaleimide PKC inhibitor conjugated to fluorescein (fim, Teflabs) and PKC activity was measured. RESULTS: 2-NN reduced ischemia/reperfusion injury as evidenced by the enhanced myocardial functional recovery, decreased LDH release after reperfusion, and decreased reperfusion arrhythmias. The PKC inhibitor attenuated myocardial functional recovery but not reperfusion arrhythmias. Cyclic AMP levels decreased after 10 min of 2-NN perfusion, compared to controls. We observed an increase in PKC activity after 2-NN treatment. CONCLUSIONS: These results suggest that PKC plays a significant role in the cardioprotective effect of 2-NN on ischemic and reperfused myocardium. The anti-arrhythmic effect of 2-NN in the reperfusion phase may be linked its action on the ATP-sensitive potassium channel itself rather than its effect on PKC activity.     

Improved energy preservation following gentle reperfusion after hypothermic, ischemic cardioplegia in infarcted rat hearts

The influence of temperature and pressure during early reperfusion after 2 h of hypothermic, cardioplegic ischemia was investigated. Adenosine triphosphate (ATP) and creatinephosphate (CP) were measured after 45-min reperfusion. The experiments were carried out in normal and previously infarcted rat hearts (the left coronary artery having been ligated 3 weeks carlier). Four groups, each containing six hearts, were studied. Group 1 consisted of normal hearts reperfused with an abrupt rise in temperature and pressure, group 2 of normal hearts exposed to slowly rising temperature and pressure, and group 3 and 4 of previously infarcted hearts. Reperfusion procedures in groups 3 and 4 were the same as in group 1 and 2, respectively. The study showed that previously infarcted hearts have a lowered tolerance to ischemia and that the reperfusion technique may influence the preservation of myocardial energetics, although this influence was not statistically significant in normal hearts following only 2 h of ischemia. The gently reperfused infarcted hearts had energy stores equal to the normal hearts after 2 h of ischemia and 45 min of reperfusion, whereas the infarcted hearts reperfused in a rougher mode had significantly lowered values (P<0.05 for ATP and P<0.01 for CP).     

The effect of chronic exogenous androgen on myocardial function following acute ischemia-reperfusion in hosts with different baseline levels of sex steroids

BACKGROUND: Gender differences exist in the myocardial response to acute ischemia/reperfusion (I/R) injury and may be attributed to the effects of the sex hormones estrogen and testosterone. The role of estrogen in myocardial injury has been extensively studied but little information exists regarding the myocardial involvement of testosterone. Based on the deleterious effects of chronic endogenous and acute testosterone exposure observed in our previous studies, we postulated that chronic exogenous testosterone administration would also exhibit deleterious effects on myocardial function following I/R. METHODS: Langendorff perfused rat hearts were subjected to 25 min ischemia, 40 min reperfusion, and left ventricular developed pressure (LVDP) was recorded. Control and 5alpha-dihydrotestosterone (DHT) treated groups each consisted of normal males, castrated males, ovariectomized (OVX) females, and senescent females. P < 0.05 = significant. RESULTS: Chronic DHT replacement therapy showed no difference in functional ischemic recovery as measured by LVDP after 40 min reperfusion in castrated males (65.1 +/- 8.13% versus 66.3 +/- 4.54%), OVX females (64.5 +/- 10.6% versus 50.2 +/- 5.97%), and senescent females (42.1 +/- 0.04% versus 41 +/- 0.05%). Interestingly, LVDP was greater in DHT treated males than control males after I/R (65.2 +/- 8.20% versus 47.6 +/- 5.19%). Also, DHT treatment resulted in significantly increased recovery of LVDP after only 10 min reperfusion in castrated males, OVX females, and senescent females compared with their untreated counterparts (54.8 +/- 11.9% versus 32.9 +/- 5.75%, 66.7 +/- 11.5% versus 43.1 +/- 8.15%, 53.4 +/- 10.1% versus 32.9 +/- 5.75%, respectively). CONCLUSION: Contrary to the adverse effects we observed in earlier studies with both endogenous and brief exogenous testosterone in myocardium injured by I/R, the present study revealed that chronic exogenous testosterone neither improved nor worsened myocardial functional recovery following 25 min ischemia and 40 min reperfusion.     

Induction of endogenous tissue antioxidant enzyme activity attenuates myocardial reperfusion injury

Efforts to reduce reperfusion injury have focused on exogenous therapies; however, endogenous attenuation of reperfusion injury can be induced by a single sublethal dose of endotoxin (ETX) prior to ischemia. The purposes of this study were to investigate (i) the early neutrophil-endothelial (PMN-EC) adherence, (ii) the associated myocardial oxidant stress, (iii) the relationship of oxidant stress to antioxidant enzyme activity, and (iv) the correlation of increased antioxidant enzyme activity to myocardial recovery following ischemia/reperfusion (I-R) injury at 36 hr. Rats were administered a sublethal dose (2% of LD50) of endotoxin (500 micrograms/kg, ip, Salmonella typhimurium). At 6 hr, myocardial neutrophil accumulation (histology), hydrogen peroxide (H2O2) levels, and myocardial tissue glutathione (glutathione and oxidized glutathione) levels were determined. At 24 hr myocardial tissue glutathione levels and catalase (CAT) activity were assayed. At 36 hr, myocardial tissue superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase, and glucose-6-phosphate dehydrogenase (G-6-PD) were assayed. At 36 hr, hearts were subjected to a standard (20 min, global, 37 degrees C) ischemic insult followed by reperfusion. At 40 min of reperfusion, ventricular function was assessed (ventricular balloon; ventricular developed pressure +dP/dt, and -dP/dt).(ABSTRACT TRUNCATED AT 250 WORDS)