p38MAPK信号通路在瑞芬太尼或缺血预处理减轻大鼠肝缺血再灌注损伤中的作用

目的 评价p38丝裂原蛋白激酶(p38MAPK)信号通路在瑞芬太尼或缺血预处理减轻大鼠肝缺血再灌注损伤中的作用.方法 健康SD大鼠l44只,雌雄不拘,体重200 ～ 250 g,采用随机数字表法,将其随机分为6组(n=24):假手术组(S组);肝缺血再灌注组(I/R组)采用动脉夹夹闭左叶和中叶肝蒂30 min,恢复灌注的方法制备大鼠肝缺血再灌注模型;瑞芬太尼组(R组)于缺血前30 min静脉输注瑞芬太尼2μg·kg-1·min-1至再灌注120 min;缺血预处理组(IPC组)于缺血前30 min行缺血5 min,再灌注5 min,重复3次后制备缺血再灌注模型;SB+R组和SB+ IPC组分别于输注瑞芬太尼或缺血预处理前5 min静脉注射p38mAPK特异性抑制剂SB203580 0.2 mg/kg,其余组给予等体积生理盐水.于再灌注30、60、90和120 min时各组分别随机取6只大鼠抽取肝下腔静脉血测定血清ALT和AST活性;采用ELISA法测定TNF-α及IL-1β浓度;随后处死大鼠,取肝组织,采用Western blot法测定磷酸化p38MAPK的表达,观察病理学结果.结果 与S组相比,I/R组各时点血清ALT、AST、TNF-α及IL-1β水平升高(P＜0.05),病理学损伤明显加重;与I/R组相比,RPC组和IPC组血清ALT和AST活性、TNF-α及IL-1β浓度降低,再灌注90 min时磷酸化p38MAPK表达上调(P＜0.05),SB+ RPC组和SB+ IPC组各指标差异无统计学意义(P＞0.05);SB+ RPC组与RPC组,SB+ IPC组和IPC组相比,血清ALT、AST、TNF-α及IL-1β水平升高,再灌注90 min时磷酸化p38MAPK表达下调(P＜0.05),病理学损伤明显加重.结论 瑞芬太尼和缺血预处理可减轻大鼠肝缺血再灌注损伤,其机制可能与激活p38MAPK信号通路抑制炎性反应有关.     

p38 MAPK在吗啡预处理对缺血-再灌注损伤心脏保护中的作用

目的 丝裂原活化蛋白激酶（MAPK）p38（p38 MAPK）是MAPK家族中重要成员之一,在缺血预处理（IPC）的保护作用信号传导机制中起着一定的作用,本研究旨在探讨p38 MAPK在吗啡预处理（MPC）对心脏缺血-再灌注损伤保护中的角色.方法 在麻醉开胸大鼠在体心脏模型,随机将54只雄性大鼠分为八组：所有心脏都经历30 min缺血和120 min再灌注,对照组（CON组,n=9）;缺血预处理组（IPC组,n=9）：在缺血-再灌注前经历3次5 min缺血,3次5 min再灌注;吗啡预处理组（MPC组,n=6）：在缺血和再灌注前5 min内分别静注吗啡100 μg/kg,再停止5 min共三个循环;SB＋MPC组（n=6）和SB＋IPC组（n=6）分别于MPC或IPC前15 min给予p38 MAPK选择性拮抗药（SB 203580）0.2 mg/kg静注.MPC＋SB组（n=6）或IPC＋SB组（n=6）分别于缺血前5min给予SB 203580 0.2 mg/kg静注.以及SB组（n=6）：缺血-再灌注前静脉给予SB 203580 0.2mg/kg.观察血流动力学指标、心肌缺血梗死区（IS/AAR）、p38 MAPK和磷酸化的p38 MAPK（pp38 MAPK）的表达.结果 MPC或IPC前应用SB 203580可以明显消除IPC的作用,但并没有消除MPC的作用.而30 min缺血前给予SB 203580可以消除MPC和IPC降低心脏IS/AAR的作用IPC组pp38 MAPK分别在缺血5 min和再灌注30 min蛋白表达密度明显高于CON组（P＜0.01）.然而在MPC组pp38 MAPK仅在再灌注30 min明显高于CON组（P＜0.01）.结论 p38 MAPK的激活是MPC对大鼠缺血后心肌保护信号机制中的介导因子而不是触发因子.     

c-Jun氨基末端激酶在瑞芬太尼预处理减轻大鼠心肌缺血再灌注损伤中的作用

目的 评价c-Jun氨基末端激酶(JNK)在瑞芬太尼预处理(RPC)减轻大鼠心肌缺血再灌注损伤中的作用.方法 成年雄性SD大鼠126只,体重300-350 g,随机分为5组:缺血再灌注组(I/R组)(n=38)、缺血预处理组(IPC组)(m=38)、RPC组(n=38)、SP+IPC组(n=6)和SP+RPC组(n=6).采用结扎左冠状动脉30 min再灌注120 min的方法制备心肌缺血再灌注模型.IPC组在缺血前30min行IPC:缺血5 min,再灌注5 min,重复3次;RPC组在缺血前30 min 行RPC:静脉输注瑞芬太尼6 ug·kg-1·min-1 5 min,停止5 min,重复3次;SP+RPC组和SP+IPC组分别于RPC或IPC前5 min腹腔注射JNK选择性阻滞剂SP600125 6 mg/kg.I/R组、IPC组和RPC组于缺血前即刻、缺血5.30 min和再灌注5、30、60 min时随机处死5只大鼠,测定左心室磷酸化JNK(p-JNK)的表达.于再灌注末处死其余大鼠,取心肌,计算左心室(LV)与右心室(RV)体积之和(LV+RV)、梗死区(IS)面积占缺血危险区(AAR)面积的百分比(IS/AAR).结果 与I/R组相比,IPC组和RPC组IS/AAR降低(P＜0.01),SP+PRC组和SP+IPC组IS/AAR差异无统计学意义(P＞0.05);缺血前即刻IPC组心肌p-JNK表达增加,缺血5min时RPC组和IPC组心肌p-JNK表达均降低,再灌注期间RPC组和IPC组心肌p-JNK表达均增加(P＜0.01).结论 JNK参与了瑞芬太尼预处理减轻大鼠心肌缺血再灌注损伤.     

p38分裂原激活蛋白激酶在小肠缺血再灌注损伤中的作用研究进展

目前国内外学者对于小肠缺血再灌注损伤的发病机制已经进行了一系列研究,其中分子机制成为研究热点.本文就p38分裂原激活蛋白激酶（p38 mitogen activated protein kinase,p38MAPK）在小肠缺血再灌注损伤发病机制中的作用（包括p38MAPK与氧化应激、炎症细胞因子、肠黏膜屏障功能、细胞凋亡的关系）以及p38MAPK在脏器缺血预处理、缺血后处理等干预措施中的研究现状作一综述.     

瑞芬太尼预处理对大鼠心肌缺血再灌注损伤的影响

目的观察瑞芬太尼预处理对大鼠心肌缺血再灌损伤的影响。方法建立50只大鼠心肌缺血再灌注损伤模型。随机分为对照组(CON组)、缺血预处理(IPC)组和瑞芬太尼预处理(RPC) 组,RPC组根据瑞芬太尼不同给药剂量又分为RPC1、RPC2、RPC3、RPC4、RPC5组,分别以0.2、0.6、2、6 和20μg·kg-1·min-1速率静脉泵注5 min,停止5 min,重复进行3次。于缺血前30 min、缺血30 min、再灌注120 min时记录心电图、收缩压、平均动脉压(MAP)、HR,计算收缩压与HR乘积(RPP)。再灌注120min时取出大鼠心脏,称心脏湿重,并制作心肌病理切片,计算左心室(LV)、右心室(RV)、缺血危险区(AAR)和梗死区(IS)的面积及体积,计算LV与RV体积之和、IS面积与AAR面积之比(IS/AAR)。结果与CON组比较,RPC2、RPC3、RPC4和RPC5组缺血30 min时MAP降低(P<0.05)。IPC、RPC1、RPC2、RPC3、RPC4、RPC5组IS和IS/AAR降低(P<0.05或0.01),心脏湿重、LV与RV体积之和、AAR 体积差异无统计学意义(P>0.05)。各组HR、RPP比较差异无统计学意义(P>0.05)。瑞芬太尼剂量-效应关系Sigmoidal方程为:Y=15.18+17.76/[1+10(-2.75-X)],ED50为2.689μg·kg-1·min-1。结论瑞芬太尼可模拟心脏缺血预处理作用,对心肌缺血再灌注损伤具有保护作用。     

瑞芬太尼预处理对大鼠离体心脏缺血再灌注损伤的保护作用

目的KATP通道在瑞芬太尼预处理对大鼠离体心脏缺血再灌注损伤保护作用中的角 色。方法 雄性SD大鼠48只,体重200～250 g,建立Langendorff大鼠离体心脏模型,随机分为6组: 每组8只。缺血再灌注组(I／R组):缺血前用Krebs-Ringer灌注液持续灌注45 min;瑞芬太尼预处理组 (RPC组):缺血前用含100μg／L瑞芬太尼的灌注液灌注5 min,停5 min,共3次。HMR RPC、5-HD RPC组分别用含1×10-4mol／L肌浆网KATP(sac-KATP)通道阻断剂HMR-1098、1×10-5mol／L线粒体KATP (mito-KATP)通道阻断剂5-羟基葵酸盐(5-HD)与上述浓度的瑞芬太尼混合液的灌注液灌注,时间从瑞 芬太尼预处理前10 min至瑞芬太尼预处理后5 min(共计45 min)。HMR、5-HD组分别在缺血前用含有 上述两种KATP通道阻断剂的灌注液灌注45 min。测定心脏稳定15 min(基础值)、缺血前即刻、缺血30 min、再灌注120 min时冠脉流量(CF);测定再灌注5、10 min时冠脉流液中乳酸脱氢酶(LDH)活性;再灌 注120 min时处死大鼠,计算心肌缺血梗死区(IS)体积及IS面积与缺血危险区面积比值(IS/AAR)。结 果 与I／R组比较,RPC、HMR RPC组IS体积和IS／AAR降低,RPC组在再灌注5、10 min时LDH活性 降低(P<0．01);5-HD RPC、HMR和5-HD组IS体积和IS／AAR差异无统计学意义(P>0．05)。与 RPC组比较,5-HD RPC、HMR和5-HD组IS体积和IS／AAR增大,5-HD RPC、HMR和5-HD组在再灌 注5、10 min时LDH活性升高(P<0．01)。与基础值相比,RPC组缺血前即刻CF增高,HMR RPC组降 低(P<0．05或0．01)。结论 通过激活心脏mito-KATP通道瑞芬太尼预处理对大鼠离体心脏缺血再灌 注损伤有一定的保护作用。     

咪唑安定预处理对缺血-再灌注离体心脏的保护作用

目的探讨咪唑安定预处理对缺血-再灌注离体心脏的保护作用。方法采用Wistar大鼠离体心脏langendofff灌注模型。实验动物随机分为四组,每组8只：正常对照组（C组）,缺血-再灌注组（I-R组）,缺血预处理组（IPC组）,咪唑安定预处理组（MPC组）。观察咪唑安定预处理对心肌缺血-再灌注后不同时间点冠脉流出液中肌酸激酶（CK）、乳酸脱氢酶（LDH）,心肌组织中超氧化物歧化酶（SOD）、髓过氧化物酶（MPO）、丙二醛（MDA）以及再灌注性心律失常、心功能的变化。结果咪唑安定预处理可以减少心肌缺血-再灌注损伤的心肌冠脉流出液中CK、LDH的含量,提高SOD活性,降低MPO、MDA水平,并且抑制再灌注心律失常的发生,保护心功能。结论咪唑安定预处理对缺血-再灌注离体心脏具有一定的保护作用。     

肝脏及肢体缺血预处理抗大鼠肝缺血再灌注损伤的实验研究

目的研究肝脏缺血预处理(经典缺血预处理IPC)的第一保护窗(FW)与肢体缺血预处理(远端缺血预处理RPC)的第二保护窗(SW)及两者联合应用对大鼠肝脏缺血再灌注(I/R)损伤的保护作用及可能机制。方法大鼠随机分成5组:I/R组不行预处理;IPC组以肝缺血5 min行预处理;RPC组以双后肢缺血5 min,反复3次行预处理;RPC+IPC组先行RPC,24 h后行IPC作预处理;S组仅行开腹,不行其他处理。3个预处理组及I/R组均行肝缺血1 h再灌注3 h。取血用于血清谷丙转氨酶(ALT)与血清谷草转氨酶(AST)检测。切取肝组织用于测定肿瘤坏死因子α(TNF-α)和热休克蛋白70(HSP70)的表达、湿干比(W/D)及观察显微、超微结构的变化。结果与I/R组比较,IPC组,RPC组及RPC+IPC组ALT,AST,W/D及TNF-α阳性表达均明显降低(P0.01),HSP70表达量明显增加(P0.01),肝脏的显微及超微结构损伤减轻;IPC,RPC,RPC+IPC组3组间各项指标差异无统计学意义(P0.05)。结论IPC的FW,RPC的SW及两者联合应用对大鼠肝脏I/R损伤均有明显的保护作用,三者在保护强度上无明显差异。其机制可能与抑制TNF-α的产生、诱导保护性蛋白HSP70的表达、减轻肝脏水肿、改善肝组织微循环有关。     

p38MAPK信号通路及其在心肌缺血再灌注损伤中的作用

心肌缺血再灌注时氧自由基和细胞因子的大量释放激活p38MAPK，然后p38MAPK把信息传到核内，引起一些早期基因的表达，如c-fos、c-jun、NF-kB，但它们的激活是保护作用还是恶化作用尚无定论。p38MAPK是否参与缺血预处理(IPC)的保护作用也无一致意见。造成这些分歧的原因主要在于实验模型和动物种类差别。     

缺血预处理对大鼠离体心脏心肌线粒体功能的影响

目的研究缺血预处理（IPC）对大鼠离体心脏心肌线粒体功能的影响。方法SD大鼠72只，随机分为4组（n=18）：对照组（CON组）、缺血再灌注组（IR组）、缺血预处理组（IPC组）和5-羟葵酸（5-HD）拮抗IPC组（5-HD＋IPC组）。采用Langendorff装置建立大鼠离体心脏缺血再灌注模型，IPC组在全心停灌前，给予2次缺血预处理，每次缺血5min，间隔5min；5-HD＋IPC组预处理前灌注5-HD 10min。各组于平衡末、缺血前、再灌注30min各取6个心脏，分离心肌线粒体并测定线粒体呼吸控制率（RCR）、磷氧比（ADP／O2）、NADH氧化酶（NADH-OX）、琥珀酸氧化酶（SUC-OX）、细胞色素C氧化酶（CYTC-OX）的活性。结果与CON组比较，IR组、IPC组和5-HD＋IPC组再灌注30min RCR、ADP／O2、NADH-OX、SUC-OX和CYTC＋OX的活性降低（P〈0．05）；与IR组比较，IPC组和5-HD＋IPC组再灌注30min上述各指标升高（P〈0．05）；与IPC组比较，5-HD＋IPC组再灌注30min上述各指标降低（P〈0．05）。结论缺血预处理可改善大鼠离体心脏缺血再灌注时心肌线粒体的功能，其机制与mitoKATP的激活有关。     

Differential activation of mitogen-activated protein kinases in ischemic and anesthetic preconditioning

BACKGROUND: Accumulating evidence pinpoints to the pivotal role of mitogen-activated protein kinases (MAPKs) in the signal transduction underlying cardiac preconditioning. METHODS: PD98059, an inhibitor of extracellular signal-regulated protein kinase (MEK-ERK1/2), and SB203580, an inhibitor of p38 MAPK, were used to evaluate the role of MAPKs with respect to postischemic functional recovery in isolated perfused rat hearts subjected to ischemic preconditioning (IPC) and anesthetic preconditioning (APC). Western blot analyses were used to determine the degree of ERK1/2 and p38 MAPK activation after the application of the preconditioning stimulus and after ischemia-reperfusion. Immunohistochemical staining served to visualize subcellular localization of activated MAPKs. RESULTS: PD98059 and SB203580 abolished postischemic functional recovery in IPC but not in APC. IPC but not APC markedly activated ERK1/2 and p38 MAPK, which were abrogated by coadministration of the specific blockers. Conversely, IPC and APC enhanced ERK1/2 activity after ischemia-reperfusion as compared to nonpreconditioned hearts, and IPC in addition enhanced p38 MAPK activity. Coadministration of PD98059 and SB203580 during IPC but not during APC inhibited postischemically enhanced MAPK activities. Moreover, chelerythrine and 5-hydroxydecanoate, effective blockers of IPC and APC, annihilated IPC- and APC-induced enhanced postischemic responses of MAPKs. Finally, administration of PD98059 during ischemia-reperfusion diminished the protective effects of IPC and APC. Immunohistochemistry revealed increased ERK1/2 activity primarily in intercalated discs and nuclei and increased p38 MAPK activity in the sarcolemma and nuclei of IPC-treated hearts. CONCLUSIONS: Although MAPKs may orchestrate cardioprotection as triggers and mediators in IPC, they are devoid of triggering, but they may have mediator effects in APC.     

Differential Activation of Mitogen-activated Protein Kinases in Ischemic and Anesthetic Preconditioning

Background: Accumulating evidence pinpoints to the pivotal role of mitogen-activated protein kinases (MAPKs) in the signal transduction underlying cardiac preconditioning.

Methods: PD98059, an inhibitor of extracellular signal-regulated protein kinase (MEK-ERK1/2), and SB203580, an inhibitor of p38 MAPK, were used to evaluate the role of MAPKs with respect to postischemic functional recovery in isolated perfused rat hearts subjected to ischemic preconditioning (IPC) and anesthetic preconditioning (APC). Western blot analyses were used to determine the degree of ERK1/2 and p38 MAPK activation after the application of the preconditioning stimulus and after ischemia-reperfusion. Immunohistochemical staining served to visualize subcellular localization of activated MAPKs.

Results: PD98059 and SB203580 abolished postischemic functional recovery in IPC but not in APC. IPC but not APC markedly activated ERK1/2 and p38 MAPK, which were abrogated by coadministration of the specific blockers. Conversely, IPC and APC enhanced ERK1/2 activity after ischemia-reperfusion as compared to nonpreconditioned hearts, and IPC in addition enhanced p38 MAPK activity. Coadministration of PD98059 and SB203580 during IPC but not during APC inhibited postischemically enhanced MAPK activities. Moreover, chelerythrine and 5-hydroxydecanoate, effective blockers of IPC and APC, annihilated IPC- and APC-induced enhanced postischemic responses of MAPKs. Finally, administration of PD98059 during ischemia-reperfusion diminished the protective effects of IPC and APC. Immunohistochemistry revealed increased ERK1/2 activity primarily in intercalated discs and nuclei and increased p38 MAPK activity in the sarcolemma and nuclei of IPC-treated hearts.     

Sevoflurane mimics ischemic preconditioning effects on coronary flow and nitric oxide release in isolated hearts.

BACKGROUND: Like ischemic preconditioning, certain volatile anesthetics have been shown to reduce the magnitude of ischemia/ reperfusion injury via activation of K+ adenosine triphosphate (ATP)-sensitive (K(ATP)) channels. The purpose of this study was (1) to determine if ischemic preconditioning (IPC) and sevoflurane preconditioning (SPC) increase nitric oxide release and improve coronary vascular function, as well as mechanical and electrical function, if given for only brief intervals before global ischemia of isolated hearts; and (2) to determine if K(ATP) channel antagonism by glibenclamide (GLB) blunts the cardioprotective effects of IPC and SPC. METHODS: Guinea pig hearts were isolated and perfused with Krebs-Ringer's solution at 55 mm Hg and randomly assigned to one of seven groups: (1) two 2-min total coronary occlusions (preconditioning, IPC) interspersed with 5 min of normal perfusion; (2) two 2-min occlusions interspersed with 5 min of perfusion while perfusing with GLB (IPC+GLB); (3) SPC (3.5%) for two 2-min periods; (4) SPC+GLB for two 2-min periods; (5) no treatment before ischemia (control [CON]); (6) CON+GLB; and (7) no ischemia (time control). Six minutes after ending IPC or SPC, hearts of ischemic groups were subjected to 30 min of global ischemia and 75 min of reperfusion. Left-ventricular pressure, coronary flow, and effluent NO concentration ([NO]) were measured. Flow and NO responses to bradykinin, and nitroprusside were tested 20-30 min before ischemia or drug treatment and 30-40 min after reperfusion. RESULTS: After ischemia, compared with before (percentage change), left-ventricular pressure and coronary flow, respectively, recovered to a greater extent (P<0.05) after IPC (42%, 77%), and treatment with SPC (45%, 76%) than after CON (30%, 65%), IPC+GLB (24%, 64%), SPC+GLB (20%, 65%), and CON+GLB (28%, 64%). Bradykinin and nitroprusside increased [NO] by 30+/-5 (means +/- SEM) and 29+/-4 nM, respectively, averaged for all groups before ischemia. [NO] increased by 26+/-6 and 27+/-7 nM, respectively, in SPC and IPC groups after ischemia, compared with an average [NO] increase of 8+/-5 nM (P<0.01) after ischemia in CON and each of the three GLB groups. Flow increases to bradykinin and nitroprusside were also greater after SPC and IPC. CONCLUSIONS: Preconditioning with sevoflurane, like IPC, improves not only postischemic contractility, but also basal flow, bradykinin and nitroprusside-induced increases in flow, and effluent [NO] in isolated hearts. The protective effects of both SPC and IPC are reversed by K(ATP) channel antagonism.     

Sevoflurane Mimics Ischemic Preconditioning Effects on Coronary Flow and Nitric Oxide Release in Isolated Hearts

Background: Like ischemic preconditioning, certain volatile anesthetics have been shown to reduce the magnitude of ischemia/ reperfusion injury viaactivation of K+ adenosine triphosphate (ATP)-sensitive (KATP) channels. The purpose of this study was (1) to determine if ischemic preconditioning (IPC) and sevoflurane preconditioning (SPC) increase nitric oxide release and improve coronary vascular function, as well as mechanical and electrical function, if given for only brief intervals before global ischemia of isolated hearts; and (2) to determine if KATP channel antagonism by glibenclamide (GLB) blunts the cardioprotective effects of IPC and SPC.

Methods: Guinea pig hearts were isolated and perfused with Krebs-Ringer's solution at 55 mmHg and randomly assigned to one of seven groups: (1) two 2-min total coronary occlusions (preconditioning, IPC) interspersed with 5 min of normal perfusion; (2) two 2-min occlusions interspersed with 5 min of perfusion while perfusing with GLB (IPC+GLB); (3) SPC (3.5%) for two 2-min periods; (4) SPC+GLB for two 2-min periods; (5) no treatment before ischemia (control [CON]); (6) CON+GLB; and (7) no ischemia (time control). Six minutes after ending IPC or SPC, hearts of ischemic groups were subjected to 30 min of global ischemia and 75 min of reperfusion. Left-ventricular pressure, coronary flow, and effluent NO concentration ([NO]) were measured. Flow and NO responses to bradykinin, and nitroprusside were tested 20-30 min before ischemia or drug treatment and 30-40 min after reperfusion.

Results: After ischemia, compared with before (percentage change), left-ventricular pressure and coronary flow, respectively, recovered to a greater extent (P < 0.05) after IPC (42%, 77%), and treatment with SPC (45%, 76%) than after CON (30%, 65%), IPC+GLB (24%, 64%), SPC+GLB (20%, 65%), and CON+GLB (28%, 64%). Bradykinin and nitroprusside increased [NO] by 30 +/- 5 (means +/- SEM) and 29 +/-4 nM, respectively, averaged for all groups before ischemia. [NO] increased by 26 +/- 6 and 27 +/- 7 nM, respectively, in SPC and IPC groups after ischemia, compared with an average [NO] increase of 8 +/- 5 nM (P < 0.01) after ischemia in CON and each of the three GLB groups. Flow increases to bradykinin and nitroprusside were also greater after SPC and IPC.     

Effects of inhibition of myocardial extracellular-responsive kinase and P38 mitogen-activated protein kinase on mechanical function of rat hearts after prolonged hypothermic ischemia

BACKGROUND: Mitogen-activated protein kinases (MAPKs), including extracellular-responsive kinase (ERK) and p38 MAPK, are activated by stresses associated with hypothermia-rewarming and ischemia-reperfusion. Their activation in heart is associated with beneficial (preconditioning) and adverse effects (apoptosis and impaired contractility). This study determined whether ERK and p38 MAPK activities are altered by hypothermic ischemia and normothermic reperfusion and the consequences of their inhibition on recovery of myocardial function. METHODS: Left ventricular work (L x min(-1) x mm Hg) was assessed during normothermic perfusion (30 min) of isolated rat hearts that were either freshly excised or previously subjected to hypothermic storage (8 hr, 3 degrees C) and rewarming (10 min, 37 degrees C) before normothermic reperfusion (30 min). Phospho-specific immunoblot analysis of p38 MAPK was performed in hearts and various cultured cells. RESULTS: Compared with fresh hearts, hearts subjected to hypothermia and rewarming demonstrated impaired left ventricular work (1.96+/-0.53, n=12 vs. 8.37+/-0.46, n=4, <0.05) during reperfusion. The ERK inhibitor, PD98059 (20 microM), present during storage and rewarming, caused modest improvement (3.66+/-0.75, n=9, <0.05). The p38 MAPK inhibitor, SB202190 (10 microM), when present during reperfusion, improved recovery (to 6.12+/-0.75, n=6, <0.05); it was ineffective if present only during rewarming (1.52+/-0.88, n=4). In rat2 fibroblasts, hypothermia and rewarming activated p38 MAPK and its downstream kinase MAPK-activated protein kinase 2, but not c-Jun N-terminal kinase/stress-activated protein kinase. CONCLUSIONS: Myocardial p38 MAPK and MAPK-activated protein kinase 2 are stimulated by hypothermia, ischemia, and rewarming and are detrimental to recovery of mechanical function of hearts subjected to prolonged hypothermic storage. Inhibition of p38 MAPK may be useful in protocols to improve the recovery of mechanical function of cold-stored hearts.     

Remifentanil preconditioning confers delayed cardioprotection in the rat

BACKGROUND: Preconditioning with remifentanil (RPC) provides immediate cardioprotection in rats via all three types of opioid (OP) receptor. This study sought to investigate whether remifentanil also confers delayed cardioprotection via OP receptors. METHODS: Male rats received preconditioning either by ischaemia (IPC; 5 min occlusion, 5 min reperfusion x 3) or with remifentanil (RPC; 1, 5, 10, and 20 microg kg(-1) min(-1), 20 min infusion). After 24 h, all animals were subjected to 30 min occlusion of the left coronary artery and 2 h of reperfusion. Subsequently, the time-course effect of RPC (10 microg kg(-1) min(-1), 20 min infusion) was determined at 12, 16, 24, 32, 36, and 48 h intervals, using the same experimental procedure. The effect of RPC (10 microg kg(-1) min(-1), 20 min infusion) and IPC in the presence of selective OP receptor antagonists was evaluated at the 24 h interval. Infarct size (IS), as a percentage of the area at risk (AAR), was determined. RESULTS: Pre-treatment with remifentanil at 1, 5, 10, and 20 microg kg(-1) min(-1) significantly reduced the IS/AAR at 24 h with the maximum effect at 10 microg kg(-1) min(-1). Remifentanil at 10 microg kg(-1) min(-1) significantly reduced the IS at 12 h [32.5 (sd 9.1)%]; 16 h [26.1 (2.8)%]; 24 h [19.5 (5.0)%]; 32 h [31.2 (9.1)%]; and 36 h [36.4 (9.4)%] after drug administration. The maximal reduction in IS was seen at 24 h and the effect completely disappeared at 48 h [36.4 (9.4)%]. The protective effect of RPC was abolished or significantly attenuated by blockade of any of the three OP receptors with selective antagonists. CONCLUSIONS: Like IPC, remifentanil produces delayed cardioprotection in anaesthetized rats 12-36 h after administration. The protective effect is mediated via all three OP receptors.     

Differences in prolonged ischemia length using ischemic preconditioning in the rabbit heart. Tolerable limitation time for surgically induced myocardial ischemia during normothermic cardiac operation

BACKGROUND: To determine the effect of the tolerable limitation time of prolonged ischemia after ischemic preconditioning on postischemic functional recovery and infarct size reduction in the rabbit heart. METHODS: White rabbits (n=30) were used for Langendorff perfusion. Control hearts were perfused at 37 degrees C for 180 min; 30 min global ischemia hearts (30GI) received 30 min global ischemia and 120 min reperfusion; IPC+30GI hearts received 5 min zero flow global ischemia and 5 min reperfusion prior to 30 min global ischemia; 20 min global ischemia hearts (20GI) received 20 min global ischemia and 120 min reperfusion; IPC+20GI hearts received 5 min zero flow global ischemia and 5 min reperfusion prior to 20 min global ischemia. RESULTS: Infarct size in the 30GI hearts was 33.5+/-4.0% and 1.7+/-0.5% in the control hearts. The 20GI hearts and IPC+30GI hearts decreased infarct size, as compared with the 30GI hearts (13.0+/-1.8% and 16.6+/-1.7%, respectively; p<0.001, 20GI vs 30GI; p<0.01, IPC+30GI vs 30GI; p>0.05, 20GI vs IPC+30GI) but did not enhance postischemic functional recovery. The IPC+20GI hearts (3.5+/-0.6%) significantly decreased infarct size as compared with the 20GI hearts (p<0.05, IPC+20GI vs 20GI), and there was no significant difference between the IPC+20GI and the control hearts (p>0.05), but the IPC+20GI hearts did not enhance postischemic functional recovery. CONCLUSIONS: A 20 min ischemia may be the tolerable limitation time of prolonged ischemia after ischemic preconditioning in an isolated rabbit heart model.     

阿片受体在异氟醚延迟预处理减轻兔心肌缺血再灌注损伤中的作用

目的 探讨阿片受体在异氟醚延迟预处理减轻兔心肌缺血再灌注损伤中的作用.方法 健康雄性新西兰大白兔40只,体重2.0～2.5 kg,采用结扎左冠状动脉前降支40 min,再灌注120 min的方法制备心肌缺血再灌注损伤模型,随机分为4组(n=10):假手术组(S组)吸入纯氧2 h,24 h后仅动脉下穿线不结扎;心肌缺血再灌注组(IR组)吸入纯氧2 h,24 h后行心肌缺血再灌注;异氟醚延迟预处理组(I组)吸人2%异氟醚2 h,24 h后行心肌缺血再灌注;阿片受体阻断剂+异氟醚延迟预处理组(N组)静脉注射纳洛酮6 mg/kg后10 min,吸入2%异氟醚2 h,24 h后行心肌缺血再灌注.于再灌注120 min时取心脏,计算心肌缺血面积和梗死面积,测定磷酸化p38MAPK蛋白表达水平,观察心肌细胞超微结构.结果 S组心肌细胞完整,排列整齐,线粒体形态正常,糖原丰富;IR组和N组心肌细胞水肿,心肌纤维排列紊乱,线粒体、内质网膜水肿,空泡化;I组心肌细胞水肿程度减轻,心肌纤维排列较完整,线粒体轻度水肿.与IR组比较,I组心肌梗死面积减小,磷酸化p38MAPK蛋白表达下调(P<0.05),N组上述指标差异无统计学意义(P>0.05).结论 阿片受体参与异氟醚延迟预处理减轻兔心肌缺血再灌注损伤.     

诱导型一氧化氮合酶在舒芬太尼预处理减轻大鼠心肌缺血再灌注损伤中的作用

目的 探讨诱导型一氧化氮合酶(iNOS)在舒芬太尼预处理减轻大鼠心肌缺血再灌注损伤中的作用.方法 成年雄性SD大鼠30只,体重250～330 g,采用随机数字表法,将大鼠随机分为5组(n=6):假手术组(S组)只穿线,不结扎;心肌缺血再灌注组(I/R组)采用结扎左冠状动脉前降支30min,再灌注120 min的方法制备大鼠心肌缺血再灌注损伤模型;舒芬太尼预处理组(SF组)缺血前24 h经尾静脉输注舒芬太尼120μg/kg,输注时间30 min;舒芬太尼预处理+iNOS特异性抑制剂S-甲硫脲组(SF+SMT组)缺血前24 h经尾静脉输注舒芬太尼120μg/kg,缺血前10 min静脉注射SMT 10 mg/kg;SMT组缺血前10 min静脉注射SMT 10 mg/kg.于缺血前30 min、缺血30 min、再灌注120 min时记录HR和MAP,计算RPP(SP× HR).于再灌注120 min时取颈动脉血样2 ml,测定血浆NO浓度,随后取心脏制病理切片,测定缺血危险区(AAR)和梗死区(IS)体积,计算心肌梗死体积(IS/AAR),测定心肌iNOS表达.结果 与S组比较,余4组再灌注120 min时MAP和RPP降低,IS/AAR升高,I/R组和SMT组缺血30 min时MAP和RPP降低(P＜0.05);与I/R组比较,SF组、SF+SMT组和SMT组HR、MAP和RPP差异无统计学意义,SF+SMT组和SMT组IS/AAR和血浆NO浓度差异无统计学意义(P＞0.05),SF组IS/AAR降低,血浆NO浓度和心肌iNOS表达升高(P＜0.05).结论 iNOS参与了舒芬太尼预处理减轻大鼠心肌缺血再灌注损伤的过程.

Abstract：

Objective To investigate the role of inducible nitric oxide synthase (iNOS) in reduction of myocardial ischemia-reperfusion (I/R) injury by sufentanil preconditioning in rats. Methods Thirty adult male SD rats, weighing 250-330 g, were randomly divided into 5 groups ( n =6 each): sham operation group (group S),I/R group, sufentanil preconditioning group (group SF), sufentanil preconditioning + a specific inhibitor of iNOS S-methyl thiourea (SMT) group (group SF+ SMT) and S-methyl thiourea group (group SMT). In I/R,SF,SF+SMT and SMT groups, myocardial I/R was produced by occlusion of left anterior descending coronary artery for 30 min followed by 120 min reperfusion. Group SF received 30 min infusion of sufentanil 120 μg/kg via caudal vein 24 h before ischemia. Group SF + SMT received infusion of sufentanil 120 μg/kg via caudal vein 24 h before ischemia and then SMT 10 mg/kg was injected 10 min before ischemia. In group SMT, SMT 10 mg/kg was injected 10min before ischemia. MAP and HR were recorded at 30 min before ischemia, at 30 min of ischemia and at the end of reperfusion. The rate-pressure product (RPP) was calculated. Arterial blood samples were obtained immediately at the end of reperfusion to determine the plasma concentration of NO. Then the animals were sacrificed and myo cardial tissues were obtained to determine the area at risk (AAR), infarct size (IS) and iNOS expression. IS/AAR was calculated. Results Compared with group S, MAP and RPP were significantly decreased, while IS/AAR was significantly increased at 120 min of reperfusion in the other four groups, and MAP and RPP were significantly decreased at 30 min of ischemia in I/R and SMT groups ( P ＜ 0.05). Compared with group I/R, no significant change was found in HR, MAP and RPP in SF, SF + SMT and SMT groups, and in IS/AAR and plasma NO concentrations in SF + SMT and SMT groups ( P ＞ 0.05), but IS/AAR was significantly decreased, and the plasma NO concentration and iNOS expression were significantly increased in group SF ( P ＜ 0. 05). Conclusion iNOS is involved in reduction of myocardial I/R injury by sufentanil preconditioning in rats.     

Does adenosine administration during the early reperfusion period affect ischemic preconditioning?

We hypothesized that the adenosine administration during the early reperfusion period might affect ischemic preconditioning (IPC) and might reduce infarct size and enhance post-ischemic functional recovery. Twenty-four anesthetized rabbits underwent 30 min. normothermic global ischemia with 120 min. reperfusion in a buffer-perfused isolated, paced heart model and divided into four groups. Global ischemic hearts (GI, n = 6) were subjected to 30 min. global ischemia without intervention. Control hearts (n=6) were subjected to perfusion without ischemia. Ischemic preconditioned hearts (IPC, n=6) were subjected to one cycle of 5 min. global ischemia and 5 min. reperfusion prior to global ischemia. IPC + Ado hearts (n=6) received IPC and adenosine administration (100 m mol/L) during 3 min. early reperfusion period. Post-ischemic functional recovery was better in IPC + Ado hearts as compared to GI and IPC hearts, but the effect of post-ischemic functional recovery in IPC + Ado hearts became weaker during 120 min. reperfusion after prolong ischemic insult. Infarct size wre 1.0 ± 0.3% in Control hearts, 32.9 ± 5.1% in GI hearts, 13.8 ± 1.3% in IPC hearts and 8.1 ± 0.9% in IPC + Ado hearts. Infarct size in IPC hearts was significantly decreased (p<0.01) as compared to GI hearts. The reduction rate against myocardial necrosis in IPC + Ado hearts versus GI hearts was higher as compared to IPC hearts versus GI hearts (p<0.001, IPC+Ado hearts vs GI hearts; p<0.01, IPC hearts vs GI hearts; p = ns, IPC + Ado hearts vs Control hearts). These data suggest that adenosine administration during the early reperfusion period reinforce IPC effect and reduce myocardial reperfusion injury. Cardiomyoprotective effects of IPC and exogenous adenosine are exerted during early reperfusion after coronary occlusion in the isolated perfused rabbit hearts.