缺血预处理及低温对幼兔心肌缺血/再灌注损伤的影响

目的：探讨缺血预处理(ischemic preconditioning,IP)及低温对幼兔心脏缺血／再灌注损伤的影响。方法：采用Langendorff离体心脏灌注模型,取3～4周龄幼兔心脏,分别给予不同次数的IP后使其在20℃低温下缺血或给予同样次数的IP后使其分别在不同低温下缺血。常温再灌注30min。记录心脏缺血／再灌注前后左心室功能指标,测定再灌注末心肌组织中ATP和丙二醛(MDA)含量,超氧化物歧化酶(SOD)及Ca^2 -ATP酶的活性。结果：再灌注末,IP2组左心室各功能指标的恢复率及心肌组织的ATP含量及Ca^2 -ATP酶的活性均显著高于Con组和IP3组;SIP1、SIP2组的左心室各功能指标的恢复率及心肌组织的ATP含量均分别显著高于SConn1组和SCon2组。其心肌组织MDA含量亦分别低于SCon1组和SCon2组。结论：IP可减轻低温缺血的幼兔心肌缺血／再灌注损伤,其效应与IP的次数和低温程度有关。     

不同温度“钾维普”停搏对幼大鼠心功能的影响

目的:探讨未成熟缺血心脏钾维普停搏保护的适宜温度。方法:离体幼大鼠心脏Langendorff法灌流,分5组(n=6～8)。对照组:36℃正常灌流170 min;36℃(常温)组:正常灌流20 min,灌钾维普停搏液(KVP)3 min停灌87 min(常温停搏90 min),恢复正常灌流(复灌)60 min;32、28、24℃(低温)组:正常灌流15 min,5 min内分别降温至32、28、24℃,灌KVP3 min停灌87 min(低温停搏90 min),复灌60 min。实验过程实时监测心率(b/min)、心肌张力(g)、收缩力(g)、最大收缩速度(dT/dtmax)、最大舒张速度(-dT/dtmax)及冠脉流量(drop/min)反映心功能。结果:与对照组相比,各组KVP停搏50 min后心脏张力均增高;与低温停搏相比,常温停搏的心脏不良挛缩迟缓、复灌后心脏张力、心率、收缩力、冠脉流量恢复好(P<0.05)。结论:未成熟缺血心脏常温钾维普停搏保护效果优于低温停搏。     

不同温度“钾维普”停搏对幼大鼠心功能的影响

目的：探讨未成熟缺血心脏“钾维普”停搏保护的适宜温度。方法：离体幼大鼠心脏Langendorff法灌流,分5组（n=6—8）。对照组：360C正常灌流170min;36℃（常温）组：正常灌流20rain,灌“钾维普”停搏液（KVe）3min停灌87min（常温停搏90rain）,恢复正常灌流（复灌）60min;32、28、24℃（低温）组：正常灌流15min,5min内分别降温至32、28、24℃,灌KVP3rain停灌87min（低温停搏90min）,复灌60min。实验过程实时监测心率（h／min）、心肌张力（g）、收缩力（g）、最大收缩速度（dr／dtmax）、最大舒张速度（-dT／dtmax）及冠脉流量（drop/min）反映心功能。结果：与对照组相比,各组KVP停搏50min后心脏张力均增高;与低温停搏相比,常温停搏的心脏不良挛缩迟缓、复灌后心脏张力、心率、收缩力、冠脉流量恢复好（P〈0．05）。结论：未成熟缺血心脏常温“钾维普”停搏保护效果优于低温停搏。     

缺血/再灌注心肌肌浆网肌钙调控蛋白mRNA表达的变化

目的：研究缺血／再灌注损伤心肌肌浆网四种钙调控蛋白mRNA表达的变化。方法：将SD大鼠分为正常对照组和缺血／再灌注损伤组,采用Langendorff离体灌流技术,全心停灌15min后行45min复灌制备缺血／再灌注模型,记录心脏收缩功能各项参数（左室发展压、＋dp／dtmax、-dp／dtmax）,进行心律失常评分,同时对两组心肌标本进行半定量RT-PCR检测,测定SERCA、PLB、IP3R2和RyR2四种蛋白质的mRNA表达水平的变化。结果：与正常对照组比较,各时间点缺血再灌注心脏左室发展压、＋dp／dtmax、-dp／dtmax均显著下降,再灌注阶段的心律失常评分明显增高,同时发现心脏SERCA,IP3R2,RyR2mRNA表达降低,然而PLBmRNA表达未出现变化。结论：缺血再灌注损伤造成心脏功能减退,心律失常增多,并可诱导心室肌钙调控蛋白SERCA、IP3R2、RyR2mRNA表达下调。     

不同剂量维拉帕米和普奈洛尔钾停搏液对幼大鼠心功能影响

目的观察含不同剂量维拉帕米和普奈洛尔的钾停搏液对未成年缺血心脏保护效应并与高钾停搏液比较,探讨适宜剂量.方法幼大鼠离体心脏Langendorff法灌流,分6组(n=8)正常组(CON)连续灌流170 min;缺血-复灌组(I-R)灌流(稳定)20min,无糖不充氧台氏液灌3 min停灌27 min连续3阵(缺血90 min),恢复正常灌流(复灌)60min;高钾停搏液(ST)和低(L)、中(M)、高(H)剂量"钾维普"保护组缺血期每阵3 min灌注用不含(ST)和含维拉帕米、普奈洛尔(×10-7mol·L-1)分别为2.0、0.34(L),6.8、1.1(M),20、3.4(H)的ST.Thomas Ⅱ号停搏液.实验过程实时动态检测心肌张力、心率、收缩力、最大收缩和舒张速度、冠脉流量、复搏时间评价,心功能.结果CON组灌流150 min心脏张力稳定,心功能降低;与CON组相比,I-R组缺血40 min后心脏挛缩,复灌后张力高,心搏功能丧失;ST组缺血60 min心肌张力升高,复灌后心功能减弱.与ST组相比,L、M、H"钾维普"呈剂量依赖性降低缺血心肌张力,复灌后心搏强;H组复搏延迟.与CON组相比,L组缺血60 min心脏张力升高,复灌后心搏弱;H组缺血40 min心脏张力低,但复灌后心搏弱;M组缺血90 min心脏张力稳定,复灌后心功能好,心搏幅度超过稳定值.结论含维拉帕米6.8×10-7mol·L-1、普奈洛尔1.1×10-7mol·L-1的钾停搏液保护常温缺血90 min幼大鼠心脏效果最佳.     

二氮嗪对自发性高血压大鼠心功能及心肌ERK和JNK表达的影响

目的:探讨二氮嗪对离体自发性高血压大鼠心脏缺血/再灌注心功能及心肌组织ERK和JNK表达的影响及可能机制。方法:雄性自发性高血压大鼠取心行Langendorff灌流。实验分为5组(n=6/组):对照组(Con)在平衡后继续灌流40min,全心缺血25min,复灌30min。其余各组除全心缺血前处理不同外,余均同对照组。缺血预处理组(IP)2次给予5min缺血+10min复灌,二氮嗪预处理组(DP)给予2次含50μmol·L-1二氮嗪的K-H液10min后给不含二氮嗪的K-H液5min,5-HD、5-HD+DP组则在平衡后给予10min150μmol·L-1线粒体KATP阻断剂5-HD,余同Con及DP组。结果:IP组及DP组复灌末左室发展压、+dP/dtmax和-dP/dtmax的恢复率均高于Con组(P<0.01),但两组左室舒张末期压恢复率低于Con组(P<0.01);5-HD能拮抗二氮嗪引起的心功能指标的改善。复灌末IP、DP及5-HD+DP组ERK表达增加。IP组及DP组心肌的JNK表达低于Con组(P<0.05),5-HD+DP组JNK表达显著高于DP组。结论:二氮嗪预处理对离体自发性高血压大鼠心肌缺血/再灌注损伤有保护作用,此保护作用可能与ERK的表达增加及JNK表达减少有关。     

心肌保护新方法—持续灌注温血心停跳液技术

心肌保护仍是目前需要进一步研究的课题。传统心肌保护研究的焦点集中在如何减轻心脏停搏时的缺血损伤或复灌后的再灌注损伤,研究结果也表明,化学性停搏加局部低温,以及复灌早期的控制性再灌注只能减轻心肌缺血再灌注损伤的程度,并不能完全消除缺血再灌注损伤。因为这些方法没有从根本上解决心脏停搏期间氧的供需矛盾,心肌缺血缺氧不可避免,对于需长时间停搏的心脏和高危病例,传统的心肌保护方法无法提供满意的心肌保护效果。近年来,心肌保护的方法有很大的发展,尤其是新近提出的持续灌注温血心脏停跳液技术,它可使心脏     

卡托普利对短时间停灌后再灌注大鼠心肌的保护作用

短时间缺血的心肌再灌注时不会发生坏死,但往往出现较长时间的舒缩功能低下等变化,这一现象被称为心肌顿抑(myocardial stunning)。预防或减轻心肌顿抑则有利于心肌再灌注时心功能的恢复。从这一考虑出发,本实验在离体大鼠工作心脏模型上,观察了再灌注时给予卡托普利(caaptopril)对20min停灌/再灌注心脏舒缩功能恢复、心肌Ca~(2 )含量和心肌乳酸脱氢酶(LDH)释放量的影响。     

L-精氨酸对大鼠心肌相对缺血/再灌注损伤保护作用的研究

目的:探索L-精氨酸(L-Arg)对心肌相对缺血/再灌损伤的保护作用,为研究抗心肌损伤的保护措施提供依据.方法:Wastar大鼠24只,随机分为对照组、相对缺血损伤组和相对缺血损伤 L-精氨酸组.采用高频阈上电刺激大鼠离体心脏建立离体心肌相对缺血/再灌注模型,分别于相对缺血前、缺血后15 min和30 min收集冠脉流出液,测定丙二醛(MDA)含量、肌酸激酶(CK)和乳酸脱氢酶(LDH)活性;采用Pclab生物信号采集处理系统测定相对缺血损伤后5 min、10 min、20 min和30 min时的心率脉压乘积(PRP)、左心室收缩压变化速率( DP/dtmax)和舒张压变化速率(-Dp/dtmAx)的恢复率.结果:L-精氨酸组的PRP、 DP/dtmax和-Dp/dtmax恢复率,明显优于相对缺血损伤组(P＜0.05);L-精氨酸组的冠脉流出液和心肌组织中的丙二醛(MDA)含量、肌酸激酶(CK)和乳酸脱氢酶(LDH)活性,低于相对缺血损伤组(P＜0.05),而L-精氨酸组的心肌超氧化物歧化酶(SOD)活性高于缺血组(P＜0.01).结论:L-精氨酸对心肌相对缺血/再灌损伤具有一定的保护作用.     

依达拉奉通过JNK对大鼠离体心肌缺血再灌注损伤的保护作用

目的:研究依达拉奉(Edaravone)对大鼠离体心肌缺血再灌注损伤的保护作用.方法:将54只SD大鼠随机分为3组,包括对照组(control group),缺血再灌注组(I/R group),依达拉奉组(Ed group).灌注液为K-H液,37℃下建立心肌缺血再灌注模型,预灌注15min,缺血30min,再灌注40 min,分别测量①复灌20和40min时心功能指标:心率(HR)、左室收缩压(LVDP)、左室舒张末压(LVEDP)、心室内压最大变化速率(±dp/dtmax),②复灌20和40 min时肌酸激酶(CK)和乳酸脱氢酶(LDH)活性,③复灌40 min时超氧化物歧化酶(SOD)活性和和丙二醛(MDA)浓度,④复灌40min时心肌梗死面积,⑤复灌40min时心肌组织中JNK的磷酸化水平.结果:①依达拉奉组的±dp/dtmax明显回升(P<0.05),同时LVEDP、LVDP等指标也有明显改善(P<0.05);②再灌注40min时,与缺血再灌注组比,依达拉奉明显降低LDH和CK;③依达拉奉能显著降低MDA浓度,同时提高SOD水平(P<0.05);④依达拉奉组心肌梗死面积小于缺血再灌注组(P<0.05);⑤依达拉奉降低缺血心肌组织中磷酸化JNK的水平(P<0.05).结论:依达拉奉可以改善缺血心肌的血流动力学,增加心肌收缩力,减少心肌梗死面积;能发挥清除氧自由基,扭转氧化与抗氧化平衡系统失调的作用;其对离体心肌缺血再灌注的保护作用可能与JNK途径密切相关.     

Cardiac preconditioning with 4-h, 17 degrees C ischemia reduces [Ca(2+)](i) load and damage in part via K(ATP) channel opening

Brief ischemia before normothermic ischemia protects hearts against reperfusion injury (ischemic preconditioning, IPC), but it is unclear whether it protects against long-term moderate hypothermic ischemia. We explored in isolated guinea pig hearts 1) the influence of two 2-min periods of normothermic ischemia before 4 h, 17 degrees C hypothermic ischemia on cardiac cytosolic [Ca(2+)], mechanical and metabolic function, and infarct size, and 2) the potential role of K(ATP) channels in eliciting cardioprotection. We found that IPC before 4 h moderate hypothermia improved myocardial perfusion, contractility, and relaxation during normothermic reperfusion. Protection was associated with markedly reduced diastolic [Ca(2+)] loading throughout both hypothermic storage and reperfusion. Global infarct size was markedly reduced from 36 +/- 2 (SE)% to 15 +/- 1% with IPC. Bracketing ischemic pulses with 200 microM 5-hydroxydecanoic acid or 10 microM glibenclamide increased infarct size to 28 +/- 3% and 26 +/- 4%, respectively. These results suggest that brief ischemia before long-term hypothermic storage adds to the cardioprotective effects of hypothermia and that this is associated with decreased cytosolic [Ca(2+)] loading and enhanced ATP-sensitive K channel opening.     

Protective effect of a low K+ cardioplegic solution on myocardial Na,K-ATPase activity.

Long duration ischemia in hypothermic conditions followed by reperfusion alters membrane transport function and in particular Na,K-ATPase. We compared the protective effect of two well-described cardioplegic solutions on cardiac Na,K-ATPase activity during reperfusion after hypothermic ischemia. Isolated perfused rat hearts (n = 10) were arrested with CRMBM or UW cardioplegic solutions and submitted to 12 hr of ischemia at 4 degrees C in the same solution followed by 60 min of reperfusion. Functional recovery and Na,K-ATPase activity were measured at the end of reperfusion and compared with control hearts and hearts submitted to severe ischemia (30 min at 37 degrees C) followed by reflow. Na,K-ATPase activity was not altered after 12 hr of ischemia and 1 hr reflow when the CRMBM solution was used for preservation (55 +/- 2 micromolPi/mg prot/hr) compared to control (53 +/- 2 micromol Pi/mg prot/hr) while it was significantly altered with UW solution (44 +/- 2 micromol Pi/mg prot/hr, p < 0.05 vs control and CRMBM). Better preservation of Na,K-ATPase activity with the CRMBM solution was associated with higher functional recovery compared to UW as represented by the recovery of RPP, 52 +/- 12% vs 8 +/- 5%, p < 0.05 and coronary flow (70 +/- 2% vs 50 +/- 8%, p < 0.05). The enhanced protection provided by CRMBM compared to UW may be related to its lower K+ content.     

The role of NO in ischemia/reperfusion injury in isolated rat heart

Nitric oxide (NO) is an important regulator of myocardial function and vascular tone under physiological conditions. However, its role in the pathological situations, such as myocardial ischemia is not unequivocal, and both positive and negative effects have been demonstrated in different experimental settings including human pathology. The aim of the study was to investigate the role of NO in the rat hearts adapted and non-adapted to ischemia. Isolated Langendorff-perfused hearts were subjected to test ischemic (TI) challenge induced by 25 min global ischemia followed by 35 min reperfusion. Short-term adaptation to ischemia (ischemic preconditioning, IP) was evoked by 2 cycles of 5 min ischemia and 5 min reperfusion, before TI. Recovery of function at the end of reperfusion and reperfusion-induced arrhythmias served as the end-points of injury. Coronary flow (CF), left ventricular developed pressure (LVDP), and dP/dt(max) (index of contraction) were measured at the end of stabilization and throughout the remainder of the protocol until the end of reperfusion. The role of NO was investigated by subjecting the hearts to 15 min perfusion with NO synthase (NOS) inhibitor L-NAME (100 mmol/l), prior to sustained ischemia. At the end of reperfusion, LVDP in the controls recovered to 29.0 +/- 3.9 % of baseline value, whereas preconditioned hearts showed a significantly increased recovery (LVDP 66.4 +/- 5.7 %, p < 0.05). Recovery of both CF and dP/dt(max) after TI was also significantly higher in the adapted hearts (101.5 +/- 5.8 % and 83.64 +/- 3.92 % ) as compared with the controls (71.9 +/- 6.3 % and 35.7 +/- 4.87 %, respectively, p < 0.05). NOS inhibition improved contractile recovery in the non-adapted group (LVDP 53.8 +/- 3.1 %; dP/dt(max) 67.5 +/- 5.92 %) and increased CF to 82.4 +/- 5.2 %. In contrast, in the adapted group, it abolished the protective effect of IP (LVDP 31.8 +/- 3.1 %; CF 70.3 +/- 3.4 % and dP/dt(max) 43.25 +/- 2.19 %). Control group exhibited 100 % occurrence of ventricular tachycardia (VT), 57 % incidence of ventricular fibrillation (VF) - 21 % of them was sustained VF (SVF); application of L-NAME attenuated reperfusion arrhythmias (VT 70 %, VF 20 %, SVF 0 %). Adaptation by IP also reduced arrhythmias, however, L-NAME in the preconditioned hearts increased the incidence of arrhythmias (VT 100 %, VF 58 %, SVF 17 %). In conclusion: our results indicate that administration of L-NAME might be cardioprotective in the normal hearts exposed to ischemia/reperfusion (I/R) alone, suggesting that NO contributes to low ischemic tolerance in the non-adapted hearts. On the other hand, blockade of cardioprotective effect of IP by L-NAME points out to a dual role of NO in the heart: a negative role in the non-adapted myocardium subjected to I/R, and a positive one, due to its involvement in the mechanisms of protection triggered by short-term cardiac adaptation by preconditioning.     

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.     

Warm ischemic preconditioning improves mitochondrial redox balance during and after mild hypothermic ischemia in guinea pig isolated hearts

Ischemic preconditioning (IPC) induces distinctive changes in mitochondrial bioenergetics during warm (37 degrees C) ischemia and improves function and tissue viability on reperfusion. We examined whether IPC before 2 h of hypothermic (27 degrees C) ischemia affords additive cardioprotection and improves mitochondrial redox balance assessed by mitochondrial NADH and flavin adenine dinucleotide (FAD) autofluorescence in intact hearts. A mediating role of ATP-sensitive K(+) (K(ATP)) channel opening was investigated. NADH and FAD fluorescence was measured in the left ventricular wall of guinea pig isolated hearts assigned to five groups of eight animals each: hypothermia alone, hypothermia with ischemia, IPC with cold ischemia, 5-hydroxydecanoic acid (5-HD) alone, and 5-HD with IPC and cold ischemia. IPC consisted of two 5-min periods of warm global ischemia spaced 5 min apart and 15 min of reperfusion before 2 h of ischemia at 27 degrees C and 2 h of warm reperfusion. The K(ATP) channel inhibitor 5-HD was perfused from 5 min before until 5 min after IPC. IPC before 2 h of ischemia at 27 degrees C led to better recovery of function and less tissue damage on reperfusion than did 27 degrees C ischemia alone. These improvements were preceded by attenuated increases in NADH and decreases in FAD during cold ischemia and the reverse changes during warm reperfusion. 5-HD blocked each of these changes induced by IPC. This study indicates that IPC induces additive cardioprotection with mild hypothermic ischemia by improving mitochondrial bioenergetics during and after ischemia. Because effects of IPC on subsequent changes in NADH and FAD were inhibited by 5-HD, this suggests that mitochondrial K(ATP) channel opening plays a substantial role in improving mitochondrial bioenergetics throughout mild hypothermic ischemia and reperfusion.     

Calcium release of heat-shocked porcine oocytes induced by thimerosal or inositol 1,4,5-trisphosphate (IP3)

The objective of this study was to determine the effect of heat shock (HS) on the Ca(2+) release and the subsequent development in matured porcine oocytes. Oocytes were matured in vitro and randomly allocated to different heat treatments at 41.5 degrees C for 1 (HS1h), 2 (HS2h) or 4h (HS4h). Control groups of oocytes were cultured for 0 or 4h without HS (39 degrees C, C0h, C4h). In Experiment 1 (eight replicates), matured oocytes were activated by thimerosal (200 microM, 10 min) following HS. Among all heated groups, maximal intracellular calcium concentration ([Ca(2+)](i)) was the highest in the HS2h. The lowest [Ca(2+)](i) peak among HS groups was observed in the HS4h, but it was higher than that in the non-heated C4h group (P<0.05). In Experiment 2 (12 replicates), each matured oocyte was injected with IP(3) (0.5mM) and the Ca(2+) transient was recorded. The peak [Ca(2+)](i) in the C4h group was still the lowest among all groups (P<0.05). Total Ca(2+) release in HS2h appeared the highest among all treatments, and it was significantly higher than that in HS1h and C4h groups (P<0.05). In order to clarify the effect of incubation time in vitro (Experiment 3), matured oocytes were cultured at 39 degrees C for 0, 2 and 4h prior to treatment with thimerosal or injected with IP(3) (three replicates). The Ca(2+) release of matured oocytes declined with the prolonged culture (P<0.05). Finally, the development of HS-oocytes was evaluated after parthenogenetic activation (Experiment 4, three replicates), and the proportion of embryos developing to the blastocysts were lower (P<0.05) in the HS groups (31+/-7% to 33+/-1%) than in the control groups (52+/-11% to 56+/-9%). We conclude that HS alters the Ca(2+)-releasing ability of matured pig oocytes, and that heat-shocked oocytes with greater Ca(2+) release incur a low developmental competence after parthenogenetic activation.     

Hypothermic preservation of the rat heart. Comparison of immersion and low-flow perfusion methods: contribution of 31P-NMR spectroscopy

Comparison of rat heart preservation by simple storage in a cardioplegic solution at 4 degrees C (6 hr for group I; 15 hr for group II) and by hypothermic low-flow perfusion of the same solution (0.3 ml min-1, 15 hr: group III) was performed by measuring biochemical and functional parameters and by collecting 31P-NMR spectroscopy data. When compared to control values, adenine nucleotide levels remained unchanged in group I hearts, while glycogen was 45% hydrolyzed and lactate level increased by 700%. Extension of heart immersion to 15 hr (group II) led to breakdown of ATP (-77%), of the sum of adenine nucleotides (-27%), and of glycogen (-77%), whereas lactate accumulation reached 900% of the control value. Functional recovery, measured at the end of a 60-min reperfusion was less than 10% in group II hearts when compared to group I hearts. This dramatic development was completely avoided by hypothermic low-flow perfusion (group III). 31P-NMR data showed that phosphocreatine was completely degraded in all groups of preserved hearts. Low-flow perfusion limited cellular acidosis. The ATP/Pi (Pi = inorganic phosphate) ratio calculated from NMR data was lower for group II hearts (0.04 +/- 0.01, n = 6) than for group I hearts (0.29 +/- 0.12; n = 6) or group III hearts (0.19 +/- 0.09; n = 6) and could constitute a convenient bioenergetic index to predict the capability of the heart to recover satisfactory contractility following a preservation period.     

Ischemic preconditioning in isolated perfused mouse heart: Reduction in infarct size without improvement of post-ischemic ventricular function

Genetically engineered mice provide an excellent tool to study the role of a particular gene in biological systems and will be increasingly used as models to understand the signal transduction mechanisms involved in ischemic preconditioning (IP). However, the phenomenon of IP has not been well characterized in this species. We therefore attempted to examine whether IP could protect isolated mouse heart against global ischemia/reperfusion (GI/R) injury. Thirty adult mice hearts were perfused at constant pressure of 55 mmHg in Langendorff mode. Following 20 min equilibration, the hearts were randomized into three groups (n = 10/each): (1) Control Group; (2) IP2.5 Group: IP with two cycles of 2.5 min GI + 2.5 min R; (3) IP5 Group: IP with 5 min GI + 5 min R. All hearts were then subjected to 20 min of GI and 30 min R (37°C). Ventricular developed force was measured by a force transducer attached to the apex. Leakage of CK and LDH was measured in coronary efflux. Infarct size was determined by tetrazolium staining. Following sustained GI/R, infarct size was significantly reduced in IP2.5 (13.8 ± 2.3%), but not in IP5 (20.1 ± 4.0%), when compared with non-preconditioned control (23.6 ± 3.8%) hearts. CK and LDH release was also reduced in both IP2.5 and IP5 groups. No significant improvement in post-ischemic ventricular contractile function was observed in either IP groups. We conclude that IP with repetitive cycles of brief GI/R is able to reduce myocardial infarct size and intracellular enzyme leakage caused by a sustained GI/R in the isolated perfused mouse heart. This anti-necrosis cardioprotection induced by IP was not associated with the amelioration of post-ischemic ventricular dysfunction.     

丙泊酚预处理对大鼠离体心肌浅低温缺血／再灌注损伤后线粒体细胞色素C释放的影响

目的：探讨丙泊酚预处理对大鼠离体心肌浅低温缺血／再灌注（I／R）损伤后心肌细胞凋亡及线粒体细胞色素C释放的影响。方法：应用Langendorff离体心脏灌注模型,取50只SD大鼠随机分为5组：对照组（C组）,二甲基亚砜（DMSO）预处理组（D组）,25、50、100μmol·L^-1丙泊酚预处理纽（P1、P2、P3组）。各组均浅低温缺血55min,再常温灌注60min。D组、P1、P2、P3组在缺血前分别以含DMSO、相应浓度丙泊酚的K-H液灌注10min,再冲洗5min,重复2次。记录平衡灌注末、缺血前即刻、再灌注30、60min时的心功能指标。再灌注60min时测定凋亡细胞,提取心肌线粒体,测定线粒体和胞浆的细胞色素C水平。结果：与C组相比,P3组再灌注30min、60min时左室舒张末压（LVEDP）降低、左室发展压（LVDP）升高（P〈0．05或P〈0．01）;P2、P3组再灌注末心肌细胞凋亡率降低（P〈0．05或P〈0．01）,线粒体细胞色素c释放减少,胞浆细胞色素C的量明显降低（P〈0．05或P〈0．01）。结论：丙泊酚预处理能够通过抑制心肌线粒体细胞色素C释放到胞浆,降低浅低温I／R损伤心肌细胞凋亡率,减轻心肌桶伤．     

环加氧酶-2抑制剂尼美舒利通过改善内皮功能和增加NO含量对抗大鼠心肌氧化应激损伤

本文旨在研究冠状动脉内皮和NO在选择性环加氧酶2（cyclooxygenase2,COX-2）抑制剂尼美舒利（nimesulide）对抗心肌氧化损伤中的作用。离体大鼠心脏行Langendorff灌流,给予H2O2（140Bmol／L）观察心脏收缩功能。用U-46619灌流心脏,使冠状动脉预收缩后,观察冠状动脉对内皮依赖性舒张因子5-HT和内皮非依赖性舒张因子硝普钠（sodiumnitroprusside,SNP）的反应。结果显示：（1）与空白对照组（100％）相比,H202灌流20min后,左心室发展压[left ventriculardevelo pedpressure,LVDP,（54．8±4．0）％],和心室内压最大变化速率【±dp／dtmax（50．8±3．1）％和（46．2±2．9）％]明显降低。H2O2灌流前尼美舒利（5μmol/L）预处理10min,能够显著抑制H2O2引起的LVDP和μdp/dtmax下降[（79．9±2．8）％,（80．3±2．6）％和（81．4±2．6）％,P〈0．0l]。（2）与空白对照组相比,H2O2灌流后,5-HT和SNP引起内皮依赖性和内皮非依赖性血管舒张功能均明显下降;而尼美舒利预处理10min能明显对抗内皮依赖性血管舒张功能的下降[（-22．2±4．2）％vsH2O2组（-6．0±2．5）％,P〈0．0l],但对其内皮非依赖性血管舒张功能的下降没有明显作用[（-2．0±1．8）％vsH202组（-7．0±3．5）％,P〉0．05]。（3）一氧化氮合酶（nitric oxide synthase,NOS）抑制剂L-NAME能够部分取消尼美舒利预处理对H20,应激心脏心功能指标的改善作用ILVDP和±dp/dtmax分别为（60．2±2．1）％,（63．9±2．4）％和（63．1±2．9）％,P〈0．01]。同时尼美舒利预处理10min能使H202应激心肌NO含量增加[（2．63±0．40）vs（1．36±0．23）nmol／gprotein,P〈0．051,而L-NAME抑制此作用。（4）选择性COX-1抑制剂吡罗昔康（piroxicam）预处理不能抑制H202引起的LVDP和±dp/dtmax下降,但促进左心室舒张末压（1eftventricular end diastolicpressure,LVEDP）升高;吡罗昔康对H202引起的内皮依赖性和内皮非依赖性血管舒张功能下降无显著作用。以上结果提示,选择性COX-2抑制剂尼美舒利能够对抗大鼠离体心肌氧化应激损伤,其机制可能是通过改善内皮依赖性血管舒张功能和增加心肌NO含量起作用。