Metabolic changes induced by ischemia and cardioplegia: a study employing cardiac microdialysis in pigs.

OBJECTIVE: The present study investigates dynamic changes of myocardial metabolism in response to ischemia, cardioplegia, and extracorporeal circulation (ECC) in order to differentiate between the contributing effects of each of these interventions. Furthermore, warm blood cardioplegia versus empty beating of the heart were compared as methods to resuscitate the ischemic myocardial metabolism. METHODS: Swedish Landrace pigs on ECC (ECC) were compared with pigs on ECC with warm ischemic cardiac arrest (ischemia) or on ECC with warm ischemic arrest followed by warm blood cardioplegia (ischemia-cardioplegia), using sham-operated pigs as controls (n=7 in each group). Microdialysis probes were placed on the surface of the left ventricle and in the femoral artery for serial evaluation of metabolites in the intracardiac extracellular fluid and arterial blood. When hearts started in ventricular fibrillation (VF), it was electroconverted after 10 min of normal blood reperfusion. If VF started after 10 min of reperfusion electroconversion was immediately performed. RESULTS: There were no differences between groups in arterial contents of serine, citrulline, arginine, inosine, hypoxanthine, guanosine, aspartate, glutamate, pyruvate, or asparagine throughout the observation period. Systemic lactate increased in pigs subjected to ischemia (P<0.001) or ischemia and cardioplegia (P=0.002), highest in the ischemia only group (P=0.002). In left ventricular microdialysates, lactate increased in pigs subjected to ischemia alone (P<0.001 vs. ECC) and ischemia and cardioplegia (P=0.004 vs. ECC). Guanosine increased in ischemia versus ECC (P=0.002), while hypoxanthine was increased in microdialysates of both ischemic (P=0.002) and ischemic-cardioplegic (P=0.001) pig hearts. Inosine was increased in pigs subjected to ischemia and cardioplegia (P<0.001 vs. ECC). All ischemic hearts started with VF, but while in the warm ischemia group VF started within 10 min of reperfusion, the ischemia-cardioplegia group had a longer asystolia with VF starting 11-22 min of blood reperfusion. CONCLUSION: The heart should be allowed to start empty beating rather than by the use of warm continuous blood cardioplegia. Microdialysis and sampling of interstitial metabolites may be advantageous when an increased sensitivity is needed or when repeated blood sampling is difficult or contraindicated in monitoring of the myocardium.     

The effects of Na+ -H+ exchange inhibitor, KB-R9032, administered at the time of reperfusion in perfused rat heart

BACKGROUND: We have reported that pretreatment with KB-R9032, a newly developed Na+ -H+ exchange inhibitor is protective against reperfusion-induced ventricular arrhythmia in the isolated perfused rat heart. This study was conducted to elucidate whether the drug is equally effective when it is given at the time of reperfusion. METHODS: Male Wistar rat hearts (n=32, 16 for each group) were perfused by means of Langendorff technique. Each heart was subjected to regional ischemia (occlusion of the left anterior descending coronary artery for 11 minutes) and to three minutes of reperfusion (release of the occlusion). KB-R9032 4 mg (one shot group) or a vehicle without drug (control) were given 30 seconds before the reperfusion to 30 seconds after the reperfusion. RESULTS: In the control group reperfusion-induced ventricular fibrillation (VF) occurred in 91.7% and the duration was 165 +/- 14.4 seconds, but, in one shot group, the incidence of VF decreased to 6.3% and the duration of VF was reduced to 0.4 +/- 0.4 seconds, respectively (P<0.05 vs control group). CONCLUSIONS: It has been shown in this study that the Na+/H+ exchange inhibitor KB-R9032 given at the time of reperfusion suppresses reperfusion arrhythmias in the ischemia-reperfusion model of isolated rat heart.     

七氟醚后处理对大鼠离体心脏缺血再灌注时心肌细胞凋亡的影响

目的 探讨七氟醚后处理对大鼠离体心脏缺血再灌注(IR)时心肌细胞凋亡的影响.方法 雄性SD大鼠48只,随机分4组(n=12),制备离体心脏灌注模型,K-H液平衡灌注30 min后,C组灌注K-H液120 min;IR组缺血30 min,K-H液再灌注90 min;缺血后处理组(IP组)缺血30 min后行4个循环复灌20 s/缺血20 s,再灌注K-H液;七氟醚后处理组(SP组)缺血30 min后灌注含七氟醚的K-H液5 min,K-H液冲洗10 min,再灌注K-H液.IP组和SP组再灌注总时间90 min.灌注期间测定心功能,灌注结束时取心脏测定心梗面积、Bcl-2、细胞色素C和Caspase-3蛋白表达水平,计算心肌细胞凋亡指数(AI).结果 与C组比较,其余各组左心室最大上升或下降速率(±dp/dt)、左心室发展压(LVDP)、HR降低,左心室舒张末压(LVEDP)和AI升高,Bel-2、细胞色素C和Caspase-3蛋白表达上调(P<0.05);与IR组比较,IP组和SP组±dp/dt、LVDP升高,LVEDP和AI降低,心梗面积减小,Bcl-2表达上调,细胞色素C和Caspase-3蛋白表达下调(P<0.05).结论 七氟醚后处理可减少大鼠离体心脏IR时心肌细胞凋亡,其机制与其下调细胞色素C和Caspase-3蛋白表达,上调Bcl-2表达有关.     

Postconditioning in females depends on injury severity

BACKGROUND: Postconditioning, a series of brief ischemia/reperfusion (I/R) cycles at reperfusion onset, is a recently described novel approach to attenuate I/R injury, and because it is an after-injury treatment strategy, it may have greater clinical potential than preconditioning. However, it has not been determined whether postconditioning is effective in women. MATERIALS AND METHODS: Adult male and female (250-300 g) Sprague-Dawley rat hearts (n = 25) were isolated, perfused via Langendorff model, and subjected to 15 min of equilibration, 20 or 25 min of global index ischemia (37 degrees C), and 40 min total reperfusion. Postconditioned hearts were subjected to 6 cycles of 10-s reperfusion/10-s ischemia immediately after release of the global index ischemia. Hearts were assigned randomly to one of four groups: 1) control hearts, 20 min index ischemia; 2) postconditioned hearts, 20 min index ischemia; 3) control hearts, 25 min index ischemia; or 4) postconditioned hearts, 25 min index ischemia. All data are reported as mean +/- SEM and were analyzed with unpaired student's t test; P < 0.05 considered significant. RESULTS: Postconditioning in female rats after 20 min of ischemia reduced depression of left ventricular-developed pressure (93.9 +/- 6.7% postconditioning recovery versus 58.6 +/- 12.6% control recovery, P < 0.05), attenuated the increase of end-diastolic pressure (P < 0.05), and reduced the depression of +dP/dT and -dP/dT (P < 0.05). The postconditioning protective effect disappeared in female rats exposed to 25 min of ischemia. The postconditioning protective effect was observed in male rats after both 20 min and 25 min ischemia. CONCLUSIONS: Postconditioning confers cardioprotection in leukocyte-free, buffer-perfused female hearts, but this protection may depend on ischemia duration. The attractive potential for the clinical application of postconditioning, however, warrants further studies to elucidate the mechanistic pathways and differences in males and female rats.     

Orthotopic transplantation of pig hearts harvested after 30 min of normothermic ischemia: controlled reperfusion with blood cardioplegia containing the Na-H-exchange inhibitor HOE 642

Objectives: The aim of our study was to develop a surgical technique for a successful transplantation of hearts harvested after 30 min of normothermic ischemia without donor pretreatment. Successful transplantation of ischemic compromised hearts could help to expand the severely limited donor pool. We used the pig model because this species is very susceptible to myocardial ischemia. Na⁺-H⁺-exchange (NHE) inhibitors have shown excellent protective properties in several in vitro and in vivo models of myocardial ischemia and reperfusion. Methods: In group I (n=12) hearts were harvested after 30 min of normothermic ischemia following cardiac arrest induced by exsanguination. Hearts were perfused with warm blood cardioplegia and transplanted orthotopically. In group II (n=9) controlled reperfusion with cold leucocyte-depleted blood cardioplegia was performed after 30 min of normothermic ischemia. In group III (n=8) the same procedure was performed as in group II but blood cardioplegia contained 1 mmol/l HOE 642. Results: In group I massive myocardial oedema was observed and none of the animals could be weaned from cardiopulmonary bypass (CPB). In contrast, all animals in groups II and III could be weaned from CPB with low dose inotropic support. In groups II and III the contractility of the hearts, expressed as maximal left and right ventricular stroke work index was significantly impaired after transplantation as compared with the preoperative value. Supplementation of blood cardioplegia with HOE 642 resulted in a significantly better recovery of the LVSWImax (Group II vs. III). Conclusions: Successful transplantation of pig hearts is possible after 30 min of normothermic ischemia without donor pretreatment if a controlled reperfusion with cold leucocyte-depleted blood cardioplegia is performed. HOE 642 given during reperfusion only improves posttransplant left ventricular function.     

Postconditioning in rats and mice

OBJECTIVE: For subsequent studies on the molecular mechanisms of postconditioning, we aimed to identify a robust postconditioning protocol in rat and mouse heart. DESIGN: Isolated rat hearts were subjected to different postconditioning protocols (study 1 and 2). The protection was compared to preconditioning. Rats (study 3) in vivo in two different laboratories were postconditioned. Isolated mouse hearts (study 4) and mice in vivo (study 5) were postconditioned. RESULTS: Postconditioning did not protect isolated, perfused rat hearts, however, preconditioning improved function and reduced infarct size. Postconditioning tended to protect rat hearts in vivo in one laboratory (p = 0.10), whereas protection was seen in the other laboratory (infarct size 51+/-11% vs controls 62+/-3%, p = 0.01). Postconditioned mouse hearts were protected, both ex vivo (16+/-9% vs controls 33+/-18%, p = 0.02) and in vivo (21+/-5% vs 42+/-7%, p < 0.001). CONCLUSIONS: Rat hearts are less suitable for studies of mechanisms of postconditioning. The results suggest that the signaling pathways differ between pre- and postconditioning. Mouse hearts were strongly protected by postconditioning, and genetically engineered mice may be useful for postconditioning research.     

Coronary effluent from postconditioned hearts promotes survival of mesenchymal stem cells under hypoxia

Objectives. Mesenchymal stem cells are sensitive to hypoxia under myocardial micro-environment of ischemia and reperfusion. Ischemic postconditioning, which is cardioprotective against ischemia–reperfusion injury, enhances in-vivo survival and therapeutic effects of transplanted stem cells. In this study, we investigated the effects of coronary effluent from postconditioned rat hearts on proliferation and survival of mesenchymal stem cells in vitro under hypoxia. Design. Isolated perfused rat hearts were divided into three groups (n = 6): the Sham group—receiving a 90 min perfusion; the Control group—receiving a 30 min global ischemia followed by a 60 min reperfusion; the ischemic postconditioning group—before sustained reperfusion, 3 cycles of 30 s reperfusion and 30 s ischemia were performed. Inflammation-related factors in coronary effluent were assessed by ELISA. Mesenchymal stem cells from bone marrow of Sprague–Dawley rats were cultured with coronary effluent under hypoxia (95% nitrogen, 5% carbon dioxide, and < 1% oxygen) for 6- or 18 h. Cell proliferation was determined by methyl thiazolyl tetrazolium. Survival rate was measured by Annexin V/PI. Results. Compared with ischemia–reperfusion treatment alone, postconditioning treatment increased the level of interleukin-10 and decreased the level of tumor necrosis factor-α and interleukin-1β in coronary effluent (P < 0.01). Stem cells cultured with postconditioned effluent, compared with those with ischemia–reperfusion effluent, had a higher proliferation (optical density value), more surviving cells, and less necrosis (P < 0.01). Conclusions. Coronary effluent from postconditioned hearts may promote the proliferation and survival of mesenchymal stem cells under hypoxia, and the suppression of inflammation may be involved in this process.     

酸处理对大鼠离体心脏缺血再灌注损伤的影响及PI3K/Akt信号通路在其中的作用

目的 评价酸处理对大鼠离体心脏缺血再灌注损伤的影响及磷脂酰肌醇-3激酶/蛋白质丝氨酸苏氨酸激酶(PI3K/Akt)信号通路在其中的作用.方法 清洁级SD大鼠70只,雌雄不拘,体重450-550 g,随机分为7组(n=10):缺血再灌注组(I/R组)、缺血后处理组(IPO组)、酸处理组(H+组)、缺血后处理+碱处理组(IPO+OH-组)、碱处理组(OH-组)、酸处理+渥曼青霉索组(H++wort组)和渥曼青霉素组(wort组).采用Langendorff装置行离体心脏灌注,采用全心停灌30 min、再灌注中性K-H液(pH值7.4)120 min的方法 制备大鼠离体心脏缺血再灌注模型.IPO组于再灌注即刻灌注中性K-H液15 s,停灌15 s,重复6次,行缺血后处理;H+组于再灌注即刻灌注经80%O2-20%CO2饱和的酸性K-H液(pH值6.9)3 min;IPO+OH-组于再灌注即刻灌注经100%O2饱和的碱性K-H液(pH值7.8)3min,并行缺血后处理;OH-组于再灌注即刻灌注碱性K-H液3 min;H++wort组于再灌注即刻灌注含100 nmol/L渥曼青霉素的酸性K-H液3 min;wort组于再灌注即刻灌注含100 nmol/L渥曼青霉素的中性K-H液3 min.于缺血前和再灌注30 min时记录左心室舒张末期压(LVEDP)和左心室压力最大上升和下降速率(±dp/dtmax);于再灌注30 min时测定冠状动脉流出液一氧化氮(NO)浓度;于再灌注120 min时,计算心肌梗塞区与缺血危险区的质量比,来表示心肌梗塞范围.结果 与I/R组比较,IPO组和H+组再灌注时LVEDP降低,±dp/dtmax升高,心肌梗塞范围减小,冠状动脉流出液NO浓度升高,OH-组、H++wort组心肌梗塞范围增加,wort组心肌梗塞范围增加,冠状动脉流出液NO浓度降低,IPO+OH-组LVEDP降低(P<0.05或0.01),±dp/dtmax、心肌梗塞范围和冠状动脉流出液NO浓度差异无统计学意义(P>0.05);IPO组与H+组上述指标比较差异均无统计学意义(P>0.05).结论 酸处理可减轻大鼠离体心脏缺血再灌注损伤.其机制与激活PI3K/Akt信号通路有关.     

Cardioprotective effect and mechanism of action of landiolol on the ischemic reperfused heart

Purpose The authors examined the cardioprotective effect of landiolol, an ultra short-acting, highly selective β1-blocker, and its role in cardiac work, antioxidative effect, and sarcoplasmic reticulum (SR) function in hearts subjected to ischemia-reperfusion. Methods Isolated guinea pig hearts were subjected to ischemia-reperfusion by stopping the perfusion for 45 min and reperfusing. Before the ischemia, hearts were treated with landiolol (20, 100, or 500 μM) for 15 min (LAN group). In another set of experiments, before ischemia, hearts were washed out for 15 min after treatment with landiolol (WO group). In other hearts, the tissue concentration of malondialdehyde was measured after reperfusion. We also examined the phosphorylation of phospholamban at Ser¹⁶ and Thr¹⁷residues to evaluate the SR function. Results After 90 min of reperfusion, left ventricular pressure (LVP) was restored significantly in the LAN-500 μM group regardless of heart rate. However, the improvement in recovery in LVP disappeared in the WO group. The tissue malondialdehyde levels were decreased in the LAN group compared with those in the control group. In the control group, the phosphorylation of phospholamban at Ser¹⁶ and Thr¹⁷ residues was markedly increased after reperfusion. Landiolol at 500 μM suppressed the increase of phosphorylation at Ser¹⁶ residues. Conclusion The present study demonstrated that landiolol had a lipid peroxidation-reducing effect and suppressed the increase in phospholamban phosphorylation at the Ser¹⁶ residue in hearts subjected to ischemia-reperfusion. These findings indicate that landiolol may have an anti-ischemic effect, via an antioxidant effect and/or via preserving SR function during the ischemic period. Presented in part at the annual meeting of the American Society of Anesthesiologists, Las Vegas, Nevada, October 23–27, 2004.     

Beneficial effects of myocardial postconditioning are associated with reduced oxidative stress in a senescent mouse model

BACKGROUND: There is at present a tragic lack of organs available for transplantation. This has led to the harvesting of hearts from older donors. Unfortunately, hearts from such donors are much more sensitive to ischemic insult. Models such as "Senescence Accelerated Mouse" Prone 8 (SAM-P8) can help understand this sensitivity. New cardioprotective techniques such as postconditioning (PostC) could be of interest in this context. We studied (1) senescence in vessels and hearts and (2) the ability of the senescent heart to adapt to an ischemia-reperfusion (I/R) sequence in the context of PostC. METHODS: Isolated working mouse hearts (8 months) were subjected to total ischemia, followed by 36 min of reperfusion; PostC was performed in the first minutes of reperfusion as three 10-sec sequences of I/R. Superoxide anion (O2.-) production was evaluated on heart and aorta cryosections with the dihydroethidium staining method. The collagen content in aortas was quantified. RESULTS: The aortas of SAM-P8 mice showed a higher production of O2.- and a higher collagen content than did those of SAM-R1 mice (P<0.05). During reperfusion, SAM-P8 hearts showed the worst recovery of cardiac output. PostC significantly reduced reperfusion dysfunction (P<0.05) and was associated with a reduction in heart O2.- staining. CONCLUSIONS: These results indicate that SAM-P8 presents a high degree of cardiovascular oxidative stress and a higher susceptibility to I/R injury, which confirms the senescence of the cardiovascular system in these animals. However, they remain sensitive to cardioprotection afforded by in vitro PostC.     

Clinical benefit of cardiac ischemic postconditioning in corrections of tetralogy of Fallot

The postoperative course of cyanotic patients is generally more complicated than in acyanotic patients. The ischemic postconditioning provides protection from myocardial injury. We conducted a randomized trial to evaluate the clinical benefits of postconditioning in patients undergoing repair of tetralogy of Fallot. Ninety-nine patients with tetralogy of Fallot were randomly assigned to ischemic postconditioning group (n=48) or control group (n=51). The postconditioning was performed by intermittent aortic clamping after reperfusion. The morbidity, mortality, ventilation time, length of ICU stay, inotropic score, release of troponin I and lactate were assayed. There was one death in postconditioned group and two in control. Major non-fatal morbidity was reduced in postconditioned patients (12.5%, 6/48) compared with control (33.3%, 17/51, P=0.016). The troponin I was significantly lower (P=0.026) with reduced inotrope score (P=0.001) and lactate release (P=0.019) in postconditioned patients. The ventilation time was significantly reduced in postconditioned patients compared with control (14+/-15 h vs. 25+/-28 h, P=0.024). There was a significant decrease in the ICU stay in the postconditioned patients (P=0.048). The study suggests that ischemic postconditioning may provide clinical benefits with respect to the morbidity, ventilation time, ICU stay, requirement of inotrope in patients undergoing repair for tetralogy of Fallot.     

Non-depolarizing cardioplegia activates Ca-ATPase in sarcoplasmic reticulum after reperfusion

Objectives: Depolarizing cardioplegia is the most common method for myocardial preservation in cardiac operations. However, depolarizing cardioplegia causes depolarization of the membrane potential by extracellular hyperkalemia, resulting in depletion of energy stores and calcium overload. This study examined the hypothesis that non-depolarizing cardioplegia would provide superior protection compared with depolarizing cardioplegia. Methods: In an isolated rat heart Langendorff model, hearts were perfused for 10 min with St. Thomas' Hospital cardioplegic solution (Group I: n=20), St. Thomas' Hospital cardioplegic solution+Lidocaine 1 mM (Group II: n=20) or non-depolarizing cardioplegia (Group III: n=20). The hearts then were subjected to 60 min of normothermic global ischemia, after which they were perfused with Krebs–Henseleit buffer at 37 °C for 30 min. The percent recovery of functional data, myocardial cyclic AMP contents, and myocardial cyclic GMP contents were recorded at each time point (base, after the administration of cardioplegia, after global ischemia, and after 30 min of reperfusion). Ca²⁺-ATPase in sarcoplasmic reticulum was measured at pre-ischemia and 30 min of reperfusion. Results: The percent recovery of developed pressure and ±dp/dt were significantly higher in Group III than in other groups. Myocardial cyclic AMP and GMP contents were elevated after reperfusion in all groups. However, in Group III, myocardial cyclic AMP contents after 30 min of reperfusion were significantly higher than in other groups (Group III: 14.7±1.6 vs. Group I: 8.7±1.0, Group II: 8.3±0.2 pmol/mg dry weight, P=0.05) but not cGMP. The sarcoplasmic reticulum Ca²⁺-ATPase activities at 30 min of reperfusion significantly increased in Group III compared with Groups II and I (Group III: 70.3±3.6 vs. Group I: 46.8±3.4, Group II: 53.9±6.1 μmol Pi/mg per h, P=0.025 and P=0.030). Conclusions: Non-depolarizing cardioplegia induced the activity of Ca²⁺-ATPase in sarcoplasmic reticulum after reperfusion. The activity would be increased by the cyclic AMP pathway. These findings suggested that non-depolarizing cardioplegia prevented calcium overload after reperfusion, especially decreased cytosolic calcium during the diastolic phase.     

In vivo chronic carvedilol treatment in rats attenuates ex vivo regional infarction of the heart

OBJECTIVE: Carvedilol is an alpha-and beta-blocking agent with antioxidant properties. We examined if treatment with carvedilol in vivo protected the heart against ischemic injury ex vivo. METHODS: Isolated hearts from treated rats (80 mg/kg/day) were subjected to 30 min regional ischemia. Hearts from non-treated animals received either no drug, 10 min carvedilol (1 microM) acute or ischemic preconditioning (IP) by 5 min ischemia +5 min reperfusion prior to regional ischemia. In separate experiments isolated hearts were subjected to 15 min global ischemia and 30 min reperfusion. RESULTS: Infarct size was significantly reduced by ischemic preconditioning or by chronic carvedilol treatment (9.0+/-0.9% and 7.2+/-1.9% of risk zone infarcted, respectively, vs. 33.8+/-6.4% in control hearts, mean+/-SEM, p < 0.05). Recovery of left ventricular developed pressure after global ischemia was not improved by carvedilol. Post-ischemic rise in left ventricular end diastolic pressure was, however, attenuated by chronic carvedilol treatment. CONCLUSION: Chronic in vivo but not acute ex vivo pretreatment with carvedilol significantly limited infarct size in isolated rat hearts.     

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.     

Efficacy of a hydroxyl radical scavenger (VF 233) in preventing reperfusion injury in the isolated rabbit heart.

We tested the hypothesis that 3,4,5,-trihydroxybenzamidoxime (VF 233), a demonstrated hydroxyl radical scavenger and an effective Fe3+ chelator, attenuates reperfusion injury and improves isovolumic left ventricular function. Eighteen isolated, perfused rabbit hearts with intracavitary balloons were subjected to normothermic, global ischemia until the initiation of ischemic contracture. Effects on the adenine nucleotide pool metabolites were determined by high-pressure liquid chromatography from right ventricular biopsy specimens before ischemia and at 15-minute intervals throughout reperfusion. In the experimental group (n = 9), a 5-mL bolus of 1 mol/L VF 233 was given immediately before reperfusion and followed by a continuous infusion (0.125 mumol/min). The control group (n = 9) received the vehicle solution at identical times. Rabbits treated with VF 233 had significant improvement in left ventricular function (expressed as percent return of left ventricular peak developed pressure) within 15 minutes of reperfusion (55.0 +/- 3.0 versus 66.2 +/- 4.1; p less than 0.05 by analysis of variance) after global ischemia and remained significantly improved throughout the reperfusion period. Myocardial adenine nucleotide pool intermediates were not significantly different between groups. These results demonstrate that administration of VF 233 significantly improves ventricular function but does not affect adenine nucleotide metabolism after ischemia and reperfusion.     

Cardioprotective effects of tetrahydrobiopterin in cold heart preservation after cardiac arrest.

BACKGROUND: It has recently been shown that tetrahydrobiopterin (BH4), an essential cofactor of nitric oxide synthase (NOS), reduces ischemia-reperfusion myocardial injury. The aim of this study was to determine if supplementation with BH4 after cardiac arrest followed by cold heart preservation would exert a cardioprotective effect against ischemia-reperfusion injury. MATERIALS AND METHODS: Isolated perfused rat hearts were subjected to 4 degrees C cold ischemia and reperfusion. Hearts were treated with cold cardioplegic solution with or without BH4 just before ischemia and during the first 5 min of reperfusion period. Effects of BH4 on left ventricular function, myocardial contents of high-energy phosphates, and nitrite plus nitrate were measured in the perfusate, before ischemia and after reperfusion. Moreover, the effect of BH4 on the cold-heart preservation followed by normothermic (37 degrees C) ischemia was determined. RESULTS: BH4 improved the contractile and metabolic abnormalities in reperfused cold preserved hearts that were subjected to normothermic ischemia. Furthermore, BH4 significantly alleviated ischemic contracture during ischemia, and restored the diminished perfusate levels of nitrite plus nitrate after reperfusion. CONCLUSION: These results demonstrated that BH4 reduces ischemia-reperfusion injury in cold heart preservation. The cardioprotective effect of BH4 implies that BH4 could be a novel and effective therapeutic option in the preservation treatment of donor heart after cardiac arrest.     

α7nAChR激动剂-缺血后处理对大鼠心肌缺血再灌注损伤的影响

目的 探讨α7烟碱型乙酰胆碱受体(α7nAChR)激动剂-缺血后处理对大鼠心肌缺血再灌注损伤的影响.方法 成年雄性SD大鼠50只,体重290～320 g,随机分为5组(n=10):假手术组(S组)、缺血再灌注组(IR组)、缺血后处理组(IP组)、α7nAChR激动剂后处理组(P组)和α7nAChR激动剂-缺血后处理组(PIP组).IR组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损伤模型;S组仅穿线不结扎;缺血30 min时IP组再灌注10 s缺血10 s,重复3次,P组腹腔注射PNU282987 2.4 mg/kg,PIP组腹腔注射PNU282987 2.4 mg/kg后行缺血后处理.于再灌注180 min时抽取右颈内静脉血样后处死大鼠,取心脏,采用ELISA法测定血清心肌肌钙蛋白Ⅰ(cTnI)、TNF-α和高迁移率族蛋白Ⅰ(HMGB1)的浓度,采用伊文蓝和TTC双重染色法测定心肌梗死体积.结果 与S组比较,其余各组心肌梗死体积、IR组血清cTnI、TNF-α和HMGB1浓度升高(P＜0.05);与IR组比较,IP组、P组和PIP组心肌梗死体积、血清cTnI、TNF-α和HMGB1浓度降低(P＜0.05);与[P组比较,PIP组心肌梗死体积、P组和PIP组血清cTnI、TNF-α和HMGB1浓度降低(P＜0.05);与P组比较,PIP组心肌梗死体积、血清TNF-α和HMGB1浓度降低(P＜0.05).结论 α7nAChR激动剂-缺血后处理减轻大鼠心肌缺血再灌注损伤的效应较单独应用时强.     

Experimental study of pegylated liposomal hemoglobin on norepinephrine release and reperfusion arrhythmias in isolated guinea pig hearts.

PURPOSE: Under myocardial reperfusion conditions, hemoglobin (Hb)-based artificial blood showed effectiveness for post-ischemic dysfunction. However, there are no studies about the effects of this product on reperfusion arrhythmias (ventricular fibrillation, VF) associated with norepinephrine (NE) release. This study was to evaluate the effects of the timing of the administration of pegylated liposomal Hb (LHb, P(50)=40-45 mmHg, 1 mg/mL) on NE release and VF. MATERIALS AND METHODS: Isolated guinea pig hearts (n=6 in each group) were randomly divided into four groups in Krebs-Henseleit solution being supplemented or not with LHb as follows: pre-ischemia (PRE), reperfusion (REP), or PRE+REP groups. The hearts were perfused for 30 min (preischemic period) and then subjected to 30 min of global ischemia, followed by 30 min of reperfusion with a normothermic Langendorff apparatus at 30 mm Hg aortic pressure in a constant pressure model. RESULTS: No differences were documented among the four groups in heart rate, left ventricular-developed pressure, or coronary flow rate. However, the REP group significantly decreased the duration of VF and NE release, but it did not inhibit the incidence of VF. CONCLUSION: These results suggest that the administration of LHb, especially with the timing of reperfusion, might prevent reperfusion arrhythmias linked to the inhibition of NE release.     

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.     

芬太尼联合七氟烷后处理对离体大鼠缺血/再灌注心功能的影响

目的 研究芬太尼联合七氟烷后处理对离体大鼠缺血/再灌注(ischemia/reperfusion,I/R)心脏心功能的影响.方法 建立离体大鼠心脏缺血40 min,再灌注120 min模型.根据再灌注开始10 min的不同处理,使用随机数字表法将实验动物随机分为4组(n=10):I/R对照组(Con),七氟烷后处理组(...