肢体缺血预处理减轻大鼠海马缺血/再灌注损伤

目的:探讨肢体缺血预处理(LIP)对大鼠全脑缺血/再灌注损伤的影响.方法: 36只大鼠椎动脉凝闭后随机分为假手术(Control)组、脑缺血组、肢体缺血组、LIP 0 d组(LIP后即刻行脑缺血)、LIP 1 d组(LIP后1 d行脑缺血)和LIP 2 d组(LIP后2 d行脑缺血).重复夹闭大鼠双侧股动脉3次(每次10 min,间隔10 min)作为LIP,夹闭颈总动脉进行全脑缺血8 min后再灌注.硫堇染色观察海马CA1区组织学分级及锥体神经元密度以判断海马损伤程度.结果:脑缺血组海马CA1区锥体神经元损伤严重,与Control组比较,组织学分级明显升高,神经元密度明显降低(P<0.01).LIP 0 d组海马CA1区神经元损伤较脑缺血组明显减轻,组织学分级明显降低,神经元密度明显升高(P<0.01).而LIP 1 d组和LIP 2 d组大鼠海马CA1区锥体细胞缺失较多,仍有明显的组织损伤.结论:LIP可减轻随后立即发生的脑缺血/再灌注损伤,但对间隔1 d后的脑缺血/再灌注损伤无显著对抗作用.     

全脑缺血模型中不同缺血时间参数对预处理保护效应的影响

目的：观察脑缺血预处理（CIP）的持续时间、CIP与后续损伤性缺血之间的间隔时间对CIP抗全脑缺血所致海马锥体神经元迟发性死亡（DND）作用的影响。方法：采用四血管闭塞法（4VO）,制作大鼠全脑缺血模型。脑组织切片硫堇染色法观察海马CA1区锥体神经元DND程度,确定组织学分级（HG）。结果：Sham组和3minCIP组海马未见DND。损伤性脑缺血组海马CA1区有明显的DND,其中6min、10min缺血组的HG为2～3级,15min缺血组的HG主要为3级。CIP＋损伤性脑缺血组中,3min-3d-6min（3minCIP后间隔三天给予6min损伤性脑缺血,下同）和3min-3d-10min组DND不明显,提示CIP可有效地保护海马CAl区神经元,防止6min或10min损伤性脑缺血诱导的DND。在3min-1d-10min组和3min-3d-15min组中,CIP的保护效应较3min-3d-10min组明显减弱。定量分析CIP对海马神经元的保护效应发现,3min-3d-6min组的神经元保护数（PN）和保护指数（PI）与3min-3d-10min组相比无明显差别（P〉0．05）;但3min-3d-10min组的神经元增长指数（GI）较3min一3d一6min组明显升高（P〈0．05）。结论：虽然3min-3d-6min组与3min-3d-10min组中CIP对神经元的保护作用相近,但3min-3d-10min组中,CIP的保护作用更容易被观察到,且CIP的保护潜能可得到最大程度的显现。应用3min-3d-10min组的时间参数建立全脑缺血耐受模型可以诱导出CIP最大的保护潜能。     

血红素氧合酶-1在离体大鼠心肌缺血预适应中的作用

目的:分别观察给予HO-1诱导剂和抑制剂对心肌相对缺血再灌注损伤和缺血预适应的影响,探讨HO-1在缺血预适应中的作用.方法:实验动物随机分为对照组(CN)、缺血/再灌损伤组(I/R)、缺血预适应 缺血/再灌损伤组(PC)、HO-1诱导剂 缺血/再灌损伤组(HM)、HO-1抑制剂 缺血预适应组(ZP).心肌缺血/再灌损伤采用相对缺血/再灌损伤模型,缺血预适应则为相对缺血5min恢复5min,反复2次.测定心功能、MDA及HO-1活性变化.结果:HM组HO-1活性升高,心功能恢复率均显著高于IR组(P＜0.01),MDA含量显著低于IR组(P＜0.05).ZP组活性降低,心功能恢复率显著低于PC组(P＜0.05),MDA含量显著高于PC组(P＜0 05).结论:HO-1是缺血预适应释放的内源性活性物质之一.     

胶质细胞谷氨酸转运体及其在脑缺血和脑缺血预适应中的变化

兴奋性氨基酸转运体(excitatory amino acid transporters,EAATs)是摄取细胞外液谷氨酸、保持细胞外谷氨酸低浓度的主要机制,已发现了五种EAATs,其中胶质细胞谷氨酸转运体在终止谷氨酸能神经传递、维持细胞外液谷氨酸浓度处于低水平方面发挥更重要作用。胶质细胞谷氨酸转运体的表达和功能受谷氨酸及其受体、垂体腺苷酸环化酶激活多肽、生长因子、内皮素、一氧化氮等许多因素的影响,其表达减少及功能降低与脑缺血损害的发生和发展密切相关,脑缺血预适应可通过调控其表达或改善其功能而诱导脑缺血耐受。     

凝闭双侧椎动脉预处理对大鼠全脑缺血损伤的防护作用

目的：观察凝闭双侧椎动脉与夹闭双侧颈总动脉之间的不同时间间隔对Pulsinelli四血管闭塞法全脑缺血模型的影响、以及在凝闭单侧椎动脉的基础上夹闭双侧颈总动脉后的脑缺血的特点。方法：84只Wistar大鼠．随机分为以下4组：对照组、双侧椎动脉凝闭组、全脑缺血组、单侧椎动脉凝闭＋双侧颈总动脉夹闭组。全脑缺血组中,根据凝闭双侧椎动脉与夹闭双侧颈总动脉之间的时间间隔不同,又分为24h间隔、48h间隔和72h间隔3个亚组。观察大鼠脑缺血过程中的反应包括瞳孔散大、对光反射等情况,脑缺血后恢复翻正反射所需要的时间、以及动物的一般状况,并应用硫堇染色法观察海马CA1区锥体神经元迟发性死亡的情况：结果：全脑缺血72h间隔亚组的大鼠,脑缺血过程中的反应、脑缺血后的一般状况和锥体神经元迟发性死亡程度均明显重于全脑缺血24h间隔亚组及48h间隔亚组,但24h间隔亚组与48h间隔亚组之间无显著差异一单侧椎动脉凝闭＋双侧颈总动脉夹闭组大鼠的凝闭侧瞳孔散大、对光反射消失、海马CA1区神经元大量死亡;而未凝闭侧未见上述相关变化。结论：凝闭双侧椎动脉本身也具有脑缺血预处理样作用,对其后48h内夹闭双侧颈总动脉所致的严重脑缺血具有一定程度的保护作用;大鼠椎动脉对脑干及海马的血液供应均存在明显的同侧优势效应,     

Early preconditioning prevents the loss of endothelial nitric oxide synthase and enhances its activity in the ischemic/reperfused rat heart

Cardiac ischemia may be responsible for either the loss of endothelial nitric oxide synthase (eNOS) or changes in its activity, both conditions leading to coronary dysfunction. We investigated whether early ischemic preconditioning was able to preserve eNOS protein expression and function in the ischemic/reperfused myocardium. Langendorff-perfused rat hearts were subjected to 20 min global ischemia, followed by 30 min reperfusion (I/R). A second group of hearts was treated as I/R, but preconditioned with three cycles of 5 min-ischemia/5 min-reperfusion (IP). Cardiac contractility markedly decreased in I/R, consistently with the rise of creatine kinase (CK) activity in the coronary effluent, whilst ischemic preconditioning significantly improved all functional parameters and reduced the release of CK. Western blot analysis revealed that the amount of eNOS protein decreased by 54.2% in I/R with respect to control (p < 0.01). On the other hand, NOS activity was not significantly reduced in I/R, as well as cGMP tissue levels, suggesting that a parallel compensatory stimulation of this enzymatic activity occurred during ischemia/reperfusion. Ischemic preconditioning completely prevented the loss of eNOS. Moreover, both NOS activity and cGMP tissue level were significantly higher (p < 0.05) in IP (12.7 +/- 0.93 pmol/min/mg prot and 58.1 +/- 12.2 fmol/mg prot, respectively) than I/R (7.34 +/- 2.01 pmol/min/mg prot and 21.4 +/- 4.13 fmol/mg prot, respectively). This suggest that early ischemic preconditioning may be useful to accelerate the complete recovery of endothelial function by preserving the level of cardiac eNOS and stimulating the basal production of nitric oxide.     

Roles of ferritin and iron in ischemic preconditioning of the heart

Iron and copper play major roles in biological systems, catalyzing free radical production and consequently causing damage. The relatively high levels of these metals, which are mobilized into the coronary flow following prolonged ischemia, have been incriminated as key players in reperfusion injury to the heart. In the present communication we investigated other roles of iron – providing protection to the ischemic heart via preconditioning (PC).PC was accomplished by subjecting isolated rat hearts to three episodes of 2 min ischemia separated by 3 min of reperfusion. Prolonged ischemia followed the PC phase. PC hearts (group I) were compared to hearts subjected to normal perfusion (group II, no ischemia) and to ischemia without PC (group III). Group I showed a marked improvement in the recovery of hemodynamic function vs. group III. Biochemical parameters further substantiated the PC protection provided to group I against prolonged ischemia. Correspondingly, group I presented markedly lower re-distribution and mobilization of iron and copper into the coronary flow, following prolonged ischemia, as evinced from the decrease in total levels, and in the 'free' fraction of iron and copper.During the PC phase no loss of cardiac function was observed. A small wave of re-distribution and mobilization of iron (typically less than 4–8% of the value of 35 min ischemia) was recorded. The cellular content of ferritin (Ft) measured in the heart was significantly higher in group I than in group III (0.90 and 0.54 g/mg, respectively). Also, iron-saturation of Ft was significantly lower for PC hearts, compared to both groups II and III (0.22 vs. 0.32 and 0.31 g/mg, for 35 min ischemia, respectively). These findings are in accord with the proposal that intracellular re-distribution and mobilization of small levels of iron, during PC, cause rapid accumulation of ferritin – the major iron-storage protein.It is proposed that iron play a dual role: (i) It serves as a signaling pathway for the accumulation of Ft following the PC phase. This iron is not involved in cardiac injury, but rather prepares the heart against future high levels of 'free' iron, thus reducing the degree of myocardial damage after prolonged ischemia. (ii) High levels of iron (and copper) are mobilized following prolonged ischemia and cause tissue damage.     

Protein kinase C is involved in cardioprotective effects of ischemic preconditioning on infarct size and ventricular arrhythmia in rats in vivo

Protein kinase C (PKC) has been known to play an important role in ischemic preconditioning (IP). This study was designed to examine whether the translocation of PKC is associated with the cardioprotective effects of IP in vivo on infarct size and ventricular arrhythmias in a rat model.Using anesthetized rats, heart rate, systolic blood pressure, infarct size and ventricular arrhythmias during 45 min of coronary occlusion were measured. PKC activity was assayed in both the cytosolic and cell membrane fraction . Brief 3-min periods of ischemia followed by 10 min of reperfusion were used to precondition the myocardium. Calphostin C was used to inhibit PKC.Infarct size was significantly reduced by IP (68.1 (2.5)%, mean (S.E.) vs. 45.2 (3.4)%, p < 0.01). The reduction in infarct size by IP was abolished by pretreatment with calphostin C. The total number of ventricular premature complex (VPC) during 45 min of coronary occlusion was reduced by IP (1474 (169) beats/45 min vs. 256 (82) beats/45 min, p < 0.05). The reduction the total number of VPC induced by IP was abolished by the administration of calphostin C before the episode of brief ischemia. The same tendency was observed in the duration of ventricular tachycardia and the incidence of ventricular fibrillation. PKC activity in the cell membrane fraction transiently increased immediately after IP (100 vs. 142%, p < 0.01) and returned to baseline 15 min after IP. Pretreatment with calphostin C prevented the translocation of PKC.The translocation of PKC plays an important role in the cardioprotective effect of IP on infarct size and ventricular arrhythmias in anesthetized rats.     

模型鼠低氧预适应适宜氧气浓度研究

目的:研究低氧预适应训练的适宜氧气浓度。方法:设计了短期和长期两种间歇性低氧暴露模式,研究了一系列不同浓度的低氧环境对模型鼠体重、血氧饱和度、游泳能力等方面的影响,进而探讨低氧预适应效应与氧气浓度之间的内在联系。结果:模型鼠长期暴露于低氧环境中,其体重增长率逐步下降;在15%～8%的低氧浓度区间,模型鼠血氧饱和度随氧气浓度降低呈现平台似缓慢下降趋势;低氧预适应训练后的模型鼠游泳能力显著提高,经在10%低氧环境中进行低氧预适应训练后的昆明小鼠游泳能力提高最为明显。结论:适当浓度的低氧预适应训练可以改善模型鼠低氧耐受能力,显著提高模型鼠运动能力。15%～10%氧气浓度区间可视为低氧预适应有益作用区间。10%氧气浓度为模型鼠低氧预适应训练的较适宜浓度。     

缺血预处理对肢体缺血／再灌注肾损伤保护作用的机制初探

目的：探讨缺血预处理对肢体缺血／再灌注时肾损伤的保护作用。方法：复制家兔肢体缺血／再灌注（I／R）损伤模型,观察肢体缺血4h再灌注4h后以及应用缺血预处理干预对肾损伤的影响。分别从右颈外静脉、肾动脉和肾静脉取血,代表外周血以及入、出肾血,观察外周血超氧化物歧化酶（SOD）、丙二醛（MDA）及尿素氮（BUN）;同时测定入肾血和出肾血NO、SOD、MDA和肾组织SOD、MDA、诱导型一氧化氮合酶（iNOS）以及缺血预处理对上述指标的影响。结果：与对照组比较,缺血再灌组松夹后4h外周血、入、出肾血及肾组织SOD活性明显降低,MDA含量增高（P〈0．01）;外周血BUN以及入、出肾血NO和肾组织iNOS含量升高（P〈0．01）;在缺血前给予缺血预处理组．SOD活性升高,而MDA、BUN、NO、iNOS含量降低（P〈0．01）。相关分析显示MDA与SOD间存在明显负相关（P〈0．01）．而MDA与NO、BUN间呈显著正相关（P〈0．01）。结论：肢体缺血／再灌注时伴有肾脏氧自由基代谢紊乱,缺血预处理可以增强肾组织的抗氧化能力,对肢体缺血再灌注肾损伤具有保护作用。     

Protaglandins and the antiarrhythmic effect of preconditioning in the isolated rat heart

Our study evaluated the relationship between the endogenous production of prostacyclin and the antiarrhythmic effect of ischemic preconditioning against ischemic and reperfusion-induced tachyarrhythmia. Langendorff perfused rat hearts underwent 30 min regional ischemia with reperfusion. Preconditioning was induced by a single episode of 5 min ischemia and 15 min reperfusion. Prostaglandin 6-keto F₁ (a stable metabolite of prostacyclin) was determined in the coronary effluent.In the control group the incidence of tachyarrhythmia was 31 % during ischemia and 67% during reperfusion. Preconditioning did not affect ischemic arrhythmias but attenuated arrhythmias a reperfusion (8%, p < 0.01) and was associated with increased release of prostacyclin prior to reperfusion. Aspirin abolished the antiarrhythmic effect of preconditioning against reperfusion tachyarrhythmias. However, no relationship was found between suppression of prostacyclin production and the occurrence of arrhythmia in individual hearts.Thus, our findings suggest that metabolites of arachidonic acid via the cyclooxygenase pathway are involved in the protective effect of ischemic preconditioning against reperfusion-induced tachyarrhythmias. (Mol Cell Biochem 160/161: 249–255, 1996)     

缺血预处理对缺血再灌注后兔脊髓磷酸腺苷代谢的影响

目的：研究缺血参处理对缺血再灌注后兔脊髓磷酸腺苷代谢的影响。方法：往置入腹主动脉的Swan-Ganz导管气囊内注气造成兔腰髓缺血模型。将实验兔分为假手术组、缺血组和预处理组。应用反相高效液相色谱方法（reverse phase HPLC),对缺血再灌注后不同时间点腰髓组织中磷酸腺苷（ATP、ADP、AMP）的含量进行检测。结果：和假手术组相比,缺血组兔再灌后各时间点腰髓组织ATP含量有明显下降（P＜0．01）。与缺血组相应时间点相比,预处理组兔再灌注后腰髓组织ATP含量明显提高（P＜0．01）。结论：缺血预处理显著提高缺血再灌注后兔脊髓组织ATP含量,这可能是缺血预处理对脊髓缺血再灌注损伤产生保护作用的机制之一。     

血红素氧合酶-1参与心肌细胞延迟预适应

目的:探讨血红素氧合酶-1(HO-1)在心肌细胞缺血预适应(IPC)中的作用。方法:实验分5组:正常对照组(CN组)、缺血/再灌注组(I/R组)、缺血预适应+缺血/再灌注组(PC组)、ZnPP(HO-1抑制剂)+缺血预适应+缺血/再灌注组(ZP组)和Hemin(HO-1诱导剂)+缺血/再灌注组(HE组)。测定HO-1mRNA表达、心肌细胞存活率、胞内[Ca2+]i和细胞培养液中MDA含量等。结果:PC组和HE组HO-1mRNA表达量和细胞存活率显著高于I/R组,而MDA含量和胞内[Ca2+]i则皆显著低于I/R组,PC组各指标与ZP组间有显著性差异,与HE组66较未见显著性差异。结论:IPC可以诱导HO-1mRNA表达,对心肌细胞缺血/再灌注损伤产生延迟保护作用。     

大鼠侧脑室注射腺苷A1受体反义寡聚脱氧核苷酸抑制脑缺血耐受的诱导

目的:观察侧脑室注射腺苷A1受体(ARA1)反义寡聚脱氧核苷酸(As-ODN)对脑缺血预处理(CIP)脑保护作用的影响,进一步探讨腺苷A1受体在CIP脑保护作用中的作用。方法:将54只凝闭双侧椎动脉的Wistar大鼠分为Sham组、CIP组、损伤性脑缺血组、CIP 损伤性脑缺血组、双蒸水 CIP 损伤性脑缺血组、ARA1As-ODN组、ARA1As-ODN CIP组、和ARA1As-ODN CIP 损伤性脑缺血组。ARA1As-ODN的剂量分为10nmol/5μl和20nmol/5μl,溶于双蒸水中,侧脑室注射。所有动物均在Sham手术后或末次全脑缺血/再灌注后7d断头取脑,硫堇染色观察海马CA1区锥体神经元迟发性死亡(DND)情况。结果:Sham组和CIP组均未见DND。与Sham、CIP组相比,损伤性脑缺血组出现了明显的DND,表现为组织学分级(HG)升高和锥体神经元密度(ND)下降(P<0.05)。CIP可显著抑制损伤性脑缺血引起的DND。与CIP 损伤性缺血组相比,ARA1As-ODN CIP 损伤性脑缺血组出现了显著的DND,表现为HG升高、ND降低(P<0.05),这种变化与ARA1As-ODN的剂量呈明显正相关。结论:腺苷A1受体As-ODN可阻断CIP诱导的脑缺血耐受,进一步证实了腺苷A1受体表达上调参与CIP诱导的脑缺血耐受。     

脑预缺血引起大鼠海马细胞膜腺苷受体数量和亲和力升高及其对神经元的保护作用

采用放射性配基结合法,测定大鼠全脑缺血后海马细胞膜腺苷(adenosine,ADO)受体数量及亲和力的变化,以探讨其与脑缺血耐受形成之间的关系。发现缺血6min即可导致海马组织明显的神经元延迟性死亡(delayed neuron     

Ischemic preconditioning is not additive to preservation with hypothermia or crystalloid cardioplegia in the globally ischemic rat heart

The aim of this study was to evaluate the additive protective efficiency of ischemic preconditioning when used in combination with conventional clinically relevant cardioprotective methods of hypothermia or hypothermic cardioplegia during sustained global ischemia.Isolated rat hearts were aorta-perfused with Krebs-Henseleit buffer and were divided into six groups (n = 10 each). Group I: Ischemia at 34°C for 60 min; Group PC+I: preconditioned (PC) ischemia at 34°C, 2 episodes of 5 min ischemia and 10 min reperfusion at 34°C followed by I; Group HI: hypothermic ischemia at 10°C for 60 min; Group PC+HI: preconditioned (PC) hypothermic ischemia, 2 episodes of 5 min ischemia and 10 min reperfusion at 34°C followed by HI; Group CPL+HI: single dose of 'Plegisol' cardioplegia followed by HI; Group PC+CPL+HI: preconditioned hypothermic cardioplegia, followed by CPL+HI. At the end of 60 min ischemia, all the hearts were reperfused at 34°C for 30 min when post-ischemic recovery in left ventricular contractile function and coronary vascular dynamics was computed and compared.There was a significant depression in the post-ischemic recovery of developed pressure (P_max), positive derivative of pressure (+dp/dt), negative derivative of pressure (-dp/dt) and heterometric autoregulation (HA) of contractile force in all the groups, with no major differences between the groups. Left ventricular end-diastolic pressure (LVEDP) was significantly elevated after I at 34°C. Preconditioning (PC+I) prevented the rise in the LVEDP and this was accompanied by a significant reduction in the release of purine metabolises in the coronary effluents, particularly adenosine, during the immediate reperfusion period. Hypothermia (HI) provided essentially the same level of metabolic and mechanical preservation as offered by PC+I. Combination of hypothermia with preconditioning (PC+HI) or cardioplegia (PC+CPL+HI), did not further enhance the preservation. Post-ischemic recovery in the regional contractile function (segment shortening, %SS) followed nearly identical pattern to global (P_max) recovery. Post-ischemic recovery in coronary flow (CF) was significantly reduced and coronary vascular resistance (CVR) was significantly increased in all the groups. Myogenic autoregulation (transient and sustained) was generally enhanced indicating increased vascular reactivity. Preconditioning did not alter the time-course of these changes.Preconditioned ischemia (34°C) preserved left ventricular diastolic functions and prevented the contracture development after sustained ischemia reperfusion at 34°C. This protective effect of preconditioning was possibly mediated by the reduction in the breakdown of purine metabolises. Hypothermia alone or in combination with crystalloid cardioplegia prevented the irreversibility of the ischemic injury but produced contractile and vascular stunning which was not improved by ischemic preconditioning. The results of this study indicate that preconditioning when combined with hypothermia or hypothermic cardioplegia offered no significant additional protection.     

Influence of extracellular potassium on the antiarrhythmic effect of global preconditioning in isolated perfused rat hearts

The objective of this study was to investigate if a variation in extracellular-K+ concentrations alters the effects of global preconditioning on ischemia-induced arrhythmias. Rat hearts were Langendorff-perfused with Krebs-Henseleit solution and randomised in 8 groups (n = 12/group): four control groups (K⁺: 2, 4, 6, or 8 mmol/L) which underwent 30-min coronary artery occlusion and four preconditioned groups (K⁺: 2, 4, 6, or 8 mmol/L) in which the 30-min regional ischemia was preceded by 2 cycles of 3 min global ischemia. In the presence of low K⁺ (2 mmol/L), there were no differences between control and preconditioning groups in the number of ventricular premature beats (VPBs): 194 ± 64 vs. 217 ± 81, the incidence of ventricular tachycardia (VT): 100% vs. 100% and of ventricular fibrillation (VF): 100% vs. 100%. In the presence of normal K⁺ concentration (4 mmol/L), ischemic preconditioning reduced the number of VPBs from 88 ± 26 to 25 ± 10, (p < 0.05), the incidence of VT from 100 to 50% (p < 0.05), and of VF from 67 to 16% (p < 0.05). In the condition of higher K⁺ concentration (6 mmol/L), VPBs (34 ± 8 vs. 11 ± 4), the incidence of VT (100% vs. 25%; p < 0.05 ) and VF (25% vs. 8%) were further reduced in preconditioned hearts. In the condition of K⁺ concentration (8 mmol/L), there were no differences in VPBs (11 ± 3 vs. 7 ± 2), the incidence of VT (8% vs. 0%) and VF (8% vs. 0%) between control and preconditioned hearts. Our data show that ischemic preconditioning affords protection against arrhythmias during coronary artery occlusion in the isolated rat heart and that hypokalemia abolishes the antiarrhythmic effects of global preconditioning.     

Mechanisms whereby glucose deprivation triggers metabolic preconditioning in the isolated rat heart

Transient glucose deprivation of the heart [GLU (-)] confers a preconditioning-like protection against subsequent ischemic/reperfusion (I/R). The mechanisms involved remain unclear. We hypothesized that GLU (-) would induce the classic ischemic preconditioning activated signaling cascade. Potential metabolic consequences and putative cell signaling events induced by transient glucose deprivation were evaluated as candidate mediators of this cardioprotection.Isolated glucose-perfused rat hearts were subjected to 30 min global ischemia followed by 30 min reperfusion (index I/R). Cardiac contractile recovery following I/R was used as the functional end-point in these studies. Metabolic preconditioning was stimulated by 15 min GLU (-) followed by 10 min glucose repletion prior to the index I/R. The potential metabolic consequences of GLU (-) were evaluated by using excess octanoate (11 mM OCT Hi) or 11 mM 2-deoxy-D-glucose (2-DG) in place of GLU (-) and by combining GLU (-) with fuels known to inhibit glycolysis supply (20 mM pyruvate or 1 mM octanoate, OCT Lo). The roles of -adrenoceptors, -adrenoceptors, adenosine receptors, protein kinase C (PKC) and mitochondrial K_ATP channels were investigated using inhibitors prazosin (10 M), propranolol (10 M), 8-(p-sulfophenyl) theophylline, (SPT 100 M), chelerythrine (CHEL 10 M) and 5-hydroxydecanoate (5 HD 100 M) respectively.GLU (-) increased mechanical recovery (59.8 ± 4.0 vs. 32.3 ± 4.7%; p < 0.01). Protection was abolished by pyruvate 26.6 ± 3.1; SPT 36.6 ± 3.0; CHEL 35 ± 4.8 or 5 HD 23.8 ± 3.3%. In a separate set of experiments, the specificity of SPT in this model was tested by preconditioning with adenosine (100 M) (34.7 ± 4 vs. control 16.8 ± 1.3%, p = 0.01) and blocking this protection with the same dose of SPT (16.3 ± 1.5%) used in the GLU (-) studies. Protection was unaltered by prazosin (50.2 ± 3.3%), propranolol (55.5 ± 4.0%), or OCT Lo (50.2 ± 2.5%). Protection was not mimicked by OCT Hi (35.6 ± 3.8%) or 2-DG (34 ± 4.3%).Transient glucose deprivation does not seem to achieve preconditioning-like cardioprotection by decreased glycolysis. Rather, the signal system may involve enhanced adenosine release, PKC, and activation of the mitochondrial K_ATP channel.     

CREB activation in the rapid, intermediate, and delayed ischemic preconditioning against hypoxic–ischemia in neonatal rat

Ischemic preconditioning (IP) is a defense program in which exposure to sublethal ischemia followed by a period of reperfusion results in subsequent resistance to severe ischemic insults. Very few in vivo IP models have been established for neonatal brain. We examined whether rapid, intermediate, and delayed IP against hypoxic–ischemia (HI) could be induced in neonatal brain, and if so, whether the IP involved phosphorylation of cAMP response element-binding protein (pCREB) after HI. Postnatal day 7 rat pups were subjected to HI at 2 h (2-h IP), 6 h (6-h IP), or 22 h (22-h IP) after IP. We found all three IP groups had significantly reduced neuronal damage and TUNEL-(+) cells 24 h post-HI than no-IP group. Compared with control, the no-IP group had significant decreases of pCREB and mitochondria Bcl-2 levels in the ipsilateral cortex 24 h post-HI. In contrast, the three IP groups had increased pCREB and mitochondria Bcl-2 levels, and significant differences were found between three IP and no-IP groups. The increases of cleavage of caspase-3 and poly (ADP-ribose) polymerase and of cells with nuclear apoptosis inducing factor post-HI in no-IP group were all significantly reduced in three IP groups. The increases of caspase-3 and calpain-mediated proteolysis of α-spectrin post-HI were significantly reduced only in 22-h IP group. Furthermore, all three IP groups had long-term neuroprotection at behavioral and pathological levels compared with no-IP group. In conclusion, IP, rapid, intermediate, or delayed, in neonatal rat brain activates CREB, up-regulates Bcl-2, induces extensive brakes on caspase-dependent and -independent apoptosis after HI, and provides long-term neuroprotection.     

缺血预处理对肢体缺血/再灌注时肺损伤的保护作用

目的：观察肢体缺血/再灌注（LI/R）时肺损伤的变化并探讨缺血预处理（IPC）对其保护作用。方法：复制家兔LI/R损伤模型,观察肢体缺血4 h再灌注4 h肺损伤的变化以及采用肢体IPC干预后对肺损伤的影响。从右颈外静脉和左颈总动脉采血,分别代表入肺血和出肺血,检测入、出肺血及肺组织超氧化物歧化酶（SOD）的活性、脂质过氧化物的代谢产物丙二醛（MDA）和一氧化氮（NO）的含量;同时测定肺组织总一氧化氮合酶（tNOS）和诱导型一氧化氮合酶（iNOS）的活性以及肢体IPC对上述指标的影响。结果：与对照组和缺血前比较,LI/R组松夹再灌注4 h入、出肺血及肺组织SOD活性明显降低,MDA和NO含量增高（P〈0.05,P〈0.01）;肺组织tNOS和iNOS活性亦升高,与对照组比较,有统计学意义（P〈0.01）。在缺血前给予IPC组,SOD活性升高,而MDA、NO含量降低,tNOS、iNOS活性也降低（P〈0.01）。相关分析显示MDA与SOD间存在明显负相关（P〈0.01）,而MDA与NO及iNOS呈显著正相关（P〈0.01）。结论：LI/R时并发的急性肺损伤与组织氧化代谢紊乱有关,IPC通过改善LI/R时肺组织氧化与抗氧化之间的平衡,进而增强肺组织的抗氧化能力,对LI/R肺损伤具有保护作用。