Ischemic preconditioning in immature hearts： mechanism and compatibility with cardioplegia

Objective To investigate (1) whether ischemic preconditioning (IPC) could protect immature rabbit hearts against ischemia-reperfusion injury and (2) the role of K(ATP) channel in the mechanism of myocardial protection. Since cardioplegia is a traditional and effective cardioprotective measure in clinic, our study is also designed to probe the compatibility between IPC and cardioplegia. Methods New Zealand rabbits aged 14-21 days weighing 220-280 g were used. The animals were anesthetized and heparinized. The chest was opened and the heart was quickly removed for connection of the aorta via Langendorff’s method within 30 s after excision. All hearts were perfused with Krebs-Henseleit buffer balanced with gas mixture (O［２］∶CO(2)=95%∶5%) at 60 cm H［2O］ (perfusion pressure). IPC consisted of 5 min global ischemia plus 10 min reperfusion. Glibenclamide was used as the K(ATP) channel blocker at a concentration of 10 μmol/L before IPC. Cardiac arrest was induced with 4℃ St. Thomas cardioplegic solution, at which point the heart was made globally ischemic by withholding perfusion for 45 min followed by 40 min reperfusion. Thirty immature rabbit hearts were randomly divided into four groups: CON (n=9) was subjected to ischemia-reperfusion only; IPC (n=9) underwent IPC and ischemia-reperfusion; Gli (n=6) was given glibenclamide and ischemia-reperfusion; and Gli+IPC (n=6) underwent glibenclamide, IPC and ischemia-reperfusion. Coronary flow (CF), HR, left ventricle developed pressure (LVDP), and ±dp/dt(max) were monitored at equilibration (baseline value) and 5, 10, 20, 30 and 40 min after reperfusion. The values resulting from reperfusion were expressed as a percentage of their baseline values. Arrhythmia quantification, myocardial enzyme in the coronary effluent and myocardial energy metabolism were also determined. Results The recovery of CF, HR, LVDP and ±dp/dt(max) in preconditioned hearts was best among the four groups. The incidence of arrhythmia was low and less CK-MB leaked out in the IPC group. Myocardial ATP content was better preserved by IPC. Pretreatment with glibenclamide completely abolished the myocardial protection provided by IPC, but did not affect ischemia-reperfusion injury. Conclusions While applying cardioplegia, IPC provides significant cardioprotective effects. Activation of K(ATP) channels is involved in the mechanism of IPC-produced cardioprotection.     

CD59 prevents human complement-mediated injuries in isolated guinea pig hearts

Objective To assess complement-mediated myocardial injury on isolated guinea pig working hearts and cardioprotective effects of CD59. Methods Using a modified Langendorff apparatus, isolated guinea-pig working hearts were perfused with a modified Krebs Henseleit buffer containing 3% heat-inactivated human plasma and zymosan （IPZ） （control） (n=10), 3% normal human plasma and zymosan （NPZ） (n=10), or 3% normal human plasma and zymosan and 1.5μg/ml CD59 （NPZC）(n=10), respectively. Epicardial electrocardiogram (ECG), cardiac output (CO), coronary arterial flow (CF), maximum left ventricular developed pressure (LVP(max)), maximum left ventricular developed pressure increase rate (+dp/dt(max)), maximum left ventricular developed pressure decrease rate (-dp/dt(max)) and heart rate (HR) were recorded at 0, 15, 30, 45 and 60 min of treatment. After the experiment, immunohistochemical examination was performed to detect the presence of C3a or C5b-9 in the myocardium of the isolated hearts.Results Compared the IPZ group, hearts treated with NPZ showed a slight depression on ST segments of epicardial ECG at 15 min, a significant elevation between 30min to 60min, a decrease in CF, CO, LVP(max), +dp/dt(max) and -dp/dt(max), and an increase in HR at 15 min. The observed alterations in CF, CO, LVP(max), +dp/dt(max) and -dp/dt(max) remained decreased, while the HR remained increased until the end of the protocol. The all above parameters of hearts treated with NPZC were similar to the control group (IPZ) at any given time. Immunohistochemical examination showed positive signals of C3a and C5b-9 in the myocardium of hearts treated with NPZ. C3a was positive in NPZC, and C3a and C5b-9 were negative in IPZ.Conclusions Activated human complements directly damage isolated guinea pig working hearts, and CD59 offers a significant protection against the injuries.     

EFFECTS OF GLIBENCLAMIDE, GLIMEPIRIDE, AND GLICLAZIDE ON ISCHEMIC PRECONDITIONING IN RAT HEART

Objective To compare the influence of different sulfonylureas on the myocardial protection effect of ischemic preconditioning (IPC) in isolated rat hearts, and ATP-sensitive potassium channel current (IKATP) of rat ventricular myocytes. Methods Isolated Langendorff perfused rat hearts were randomly assigned to five groups: (1) control group, (2) IPC group, (3) IPC glibenclamide (GLB, 10 μmol/L) group, (4) IPC glimepiride (GLM, 10 μmol/L) group, (5) IPC gliclazide (GLC, 50 μmol/L) group. IPC was defined as 3 cycles of 5-minute zero-flow global ischemia followed by 5-minute reperfusion. The haemodynamic parameters and the infarct size of each isolated heart were recorded. And the sarcolemmal IKATP of dissociated ventricular myocytes reperfused with 10 μmol/L GLB, 1 μmol/L GLM, and 1 μmol/L GLC was recorded with single-pipette whole-cell voltage clamp under simulated ischemic condition. Results The infarct sizes of rat hearts in IPC (23.7%±1.3%), IPC GLM (24.6%±1.0%), and IPC GLC (33.1%±1.3%) groups were all significantly smaller than that in control group (43.3%±1.8%; P<0.01, n=6). The infarct size of rat hearts in IPC GLB group (40.4%±1.4%) was significantly larger than that in IPC group (P<0.01, n=6). Under simulated ischemic condition, GLB (10 μmol/L) decreased IKATP from 20.65±7.80 to 9.09±0.10 pA/pF (P<0.01, n=6), GLM (1 μmol/L) did not significantly inhibit IKATP (n=6), and GLC (1 μmol/L) decreased IKATP from 16.73±0.97 to 11.18±3.56 pA/pF(P<0.05, n=6). Conclusions GLM has less effect on myocardial protection of IPC than GLB and GLC. Blockage of sarcolemmal ATP-sensitive potassium channels in myocardium might play an important role in diminishing IPC-induced protection of GLM, GLB, and GLC.     

联合应用缺血后处理、远隔缺血后处理和纳洛酮后处理对大鼠脑缺血-再灌注损伤的影响

Objective To assess the effects of ischemic postconditioning, remote ischemic postconditioning and naloxone postconditioning on focal cerebral ischemia-reperfusion injury in rats.Methods A total of 110 adult SD rats were randomly divided into 5 groups (n =22 each). The focal cerebral ischemia-reperfusion injury was induced by a 90-minute occlusion of right middle cerebral artery (MCA) and a 24-hour reperfusion sequentially. Group 1 was of ischemia-reperfusion control; Group 2 ischemic postconditioning induced by three 30-second cycles of MCA occlusion followed by a 30-second reperfusion; Group 3 remote ischemic postconditioning performed via a transient occlusion of right femoralartery at 5 min before the initiatlon of reperfusion:Group 4 naloxone posteonditioning with naloxone 10 mg/kg intraperitoneaUy injected at the initiation of reperfusion;Group 5 combined ischemic,remote ischernic & naloxone postconditioning performed simultaneously in accordance with the methods used in Groups 2,3 & 4.The neumlogie deftcit scores(NDS)were obtained at 2 h & 24 h post-reperfusion.At 24 h post-reperfusion.the anesthetized rat was sacrificed by decapitation and the brain rapidly extracted to asseSS the size ofcerebral infaret(n=10),detect the cerebral expression of microtubule-associated protein2(MAP2)(n=6),measure the plasma volume of cerebral tissues and quantify the diameter and segment artery at 5 min before the initiation of reperfusion; Group 4 naloxone postconditioning with naloxone 10 mg/kg intraperitoneally injected at the initiation of reperfusion; Group 5 combined ischemic, remote ischemic & naloxone postconditioning performed simultaneously in accordance with the methods used in Groups 2, 3 & 4. The neurologic deficit scores ( NDS) were obtained at 2 h & 24 h post-reperfusion. At 24 h post-reperfusion, the anesthetized rat was sacrificed by decapitation and the brain rapidly extracted to assess the size of cerebral infarct (n = 10), detect the cerebral expression of microtubule-associated protein2 ( MAP2) (n =6) , measure the plasma volume of cerebral tissues and quantify the diameter and segment length of cerebral microvessel (n = 6 ). Results There were no significant differences in the heart rate (HR) and mean arterial pressure (MAP) among the above five groups at all observed time points (P ＞ 0. 05). At 24 h post-reperfusion, the percentage of ischemic cerebral infarct size was 43% ±6% , 31% ±4% , 32% ±5% , 28% ±6% & 21% ±7% in ipsilateral hemisphere area (i. e. , cerebral infarct severity)in Groups 1-5 respectively. Compared with Group 1, the levels of NDS and cerebral infarct severity significantly decreased at ischemic side in Groups 2-5 ( P ＜ 0. 05 ). And the cerebral expression of MAP2,plasma volume of cerebral tissues, diameter and segment length of cerebral microvessel significantly increased at the ischemic side (all P＜0. 05). However, there were no significant differences in the abovementioned parameters at ischemic side among Groups 2, 3 and 4 (all P ＞0. 05). The parameters of NDS,cerebral infarct severity, cerebral expression of MAP2 and plasma volume of cerebral tissues in the ischemic side significantly increased in Group 5 compared with Groups 1,2,3 and 4 (all P ＜ 0. 05). The diameter and segment length of cerebral microvessel at ischemic side were not different among Groups 2,3,4 and 5 (all P＞0. 05). Conclusion In focal cerebral ischemia-reperfusion rats, ischemic, remote ischemic and naloxone postconditioning may produce significant neuroprotective effects of reduced cerebral infarct severity and improved neurologic dysfunctions. A combination of three postconditioning approaches enhances the above neuroprotective effects.     

联合应用缺血后处理、远隔缺血后处理和纳洛酮后处理对大鼠脑缺血-再灌注损伤的影响

Objective To assess the effects of ischemic postconditioning, remote ischemic postconditioning and naloxone postconditioning on focal cerebral ischemia-reperfusion injury in rats.Methods A total of 110 adult SD rats were randomly divided into 5 groups (n =22 each). The focal cerebral ischemia-reperfusion injury was induced by a 90-minute occlusion of right middle cerebral artery (MCA) and a 24-hour reperfusion sequentially. Group 1 was of ischemia-reperfusion control; Group 2 ischemic postconditioning induced by three 30-second cycles of MCA occlusion followed by a 30-second reperfusion; Group 3 remote ischemic postconditioning performed via a transient occlusion of right femoralartery at 5 min before the initiatlon of reperfusion:Group 4 naloxone posteonditioning with naloxone 10 mg/kg intraperitoneaUy injected at the initiation of reperfusion;Group 5 combined ischemic,remote ischernic & naloxone postconditioning performed simultaneously in accordance with the methods used in Groups 2,3 & 4.The neumlogie deftcit scores(NDS)were obtained at 2 h & 24 h post-reperfusion.At 24 h post-reperfusion.the anesthetized rat was sacrificed by decapitation and the brain rapidly extracted to asseSS the size ofcerebral infaret(n=10),detect the cerebral expression of microtubule-associated protein2(MAP2)(n=6),measure the plasma volume of cerebral tissues and quantify the diameter and segment artery at 5 min before the initiation of reperfusion; Group 4 naloxone postconditioning with naloxone 10 mg/kg intraperitoneally injected at the initiation of reperfusion; Group 5 combined ischemic, remote ischemic & naloxone postconditioning performed simultaneously in accordance with the methods used in Groups 2, 3 & 4. The neurologic deficit scores ( NDS) were obtained at 2 h & 24 h post-reperfusion. At 24 h post-reperfusion, the anesthetized rat was sacrificed by decapitation and the brain rapidly extracted to assess the size of cerebral infarct (n = 10), detect the cerebral expression of microtubule-associated protein2 ( MAP2) (n =6) , measure the plasma volume of cerebral tissues and quantify the diameter and segment length of cerebral microvessel (n = 6 ). Results There were no significant differences in the heart rate (HR) and mean arterial pressure (MAP) among the above five groups at all observed time points (P ＞ 0. 05). At 24 h post-reperfusion, the percentage of ischemic cerebral infarct size was 43% ±6% , 31% ±4% , 32% ±5% , 28% ±6% & 21% ±7% in ipsilateral hemisphere area (i. e. , cerebral infarct severity)in Groups 1-5 respectively. Compared with Group 1, the levels of NDS and cerebral infarct severity significantly decreased at ischemic side in Groups 2-5 ( P ＜ 0. 05 ). And the cerebral expression of MAP2,plasma volume of cerebral tissues, diameter and segment length of cerebral microvessel significantly increased at the ischemic side (all P＜0. 05). However, there were no significant differences in the abovementioned parameters at ischemic side among Groups 2, 3 and 4 (all P ＞0. 05). The parameters of NDS,cerebral infarct severity, cerebral expression of MAP2 and plasma volume of cerebral tissues in the ischemic side significantly increased in Group 5 compared with Groups 1,2,3 and 4 (all P ＜ 0. 05). The diameter and segment length of cerebral microvessel at ischemic side were not different among Groups 2,3,4 and 5 (all P＞0. 05). Conclusion In focal cerebral ischemia-reperfusion rats, ischemic, remote ischemic and naloxone postconditioning may produce significant neuroprotective effects of reduced cerebral infarct severity and improved neurologic dysfunctions. A combination of three postconditioning approaches enhances the above neuroprotective effects.     

Prevention of Regional Ischemic-Reperfused Myocardial Damages in the Isolated Working Rat Hearts by Puerarin

The performances of the isolated working rat hearts perfusedwith modified K-H solution were stable for 90 min of perfusion time.However, the contractility and the total cardiac output decreasedsignificantly after 120 min. The acute regional ischemia produced by theligation of left main coronary artery in the isolated working rat hearts wasfollowed by decrease in cardial power production and increase in creatinephosphokinase release. Coronary flow restored to the preligation valueimmediately after the beginning of reperfusion following 30 min regionalischemia, but the cardiac function (as measured by total cardiac output andpower production) did not recover significantly and the creatinephosphokinase release even further increased during 15 min reperfusion.1.4 × 10~(-4) M puerarin significantly increased coronary flow and did notaffect other mechanical performances of the normal isolated working rathearts. However, 10~(-5)M propranolol as well as 1.4 × 10~(-4) M puerarinreduced significantly the creatine phosphokinase release from the regionalischemic-reperfused myocardium and accelerated the recovery of the cardiacfunction during reperfusion time in the isolated working rat hearts. Theresults suggested that both puerarin and propranolol have direct benificialeffects on the ischemic-reperfused myocardium.     

Carvedilol attenuates CPB-induced apoptosis in dog heart: regulation

Objective To evaluate the effects of Carvedilol on cardiopulmonary bypass (CPB)-induced myocardiocyte apoptosis and its effect on regulation of Fas, FasL expression, caspase-3 activity and oxidative stress in the left ventricle (LV) in this setting.Methods Ten adult dogs undergoing conventional hypothermic CPB were randomly divided into control and Carvedilol treated groups (n=5, respectively). Dogs in Carvedilol treated group 3 μg·min-1·kg-1 received a bolus of Carvedilol (1 mg/kg) intravenously and a maintenance dosage of Carvedilol for 3 hours after the reperfusion of the heart. Dogs in control group received no carvediolol. LV samples were obtained before, during and 3 hours after CPB. In situ nick end-labeling (TUNEL) technique was used to detect the apoptotic cells. The expressions of Fas and FasL were detected immunohistochemically and quantified by fluorescence activated cell sorting (FACS). The activity of caspase-3 enzyme and malondialdehyde (MDA) level were measured by cleavage of Z-DEVD-AMC substrate and thiobarbituric acid reactive substances (TBARS) method, respectively. Results Before and during CPB, all the parameters were not significantly different between groups (P&gt;0.05). After CPB, these parameters in both groups were significantly elevated compared with those of before and during CPB (P&lt;0.028, respectively). However, the number of apoptotic cells in Carvedilol treated group was significantly decreased compared with that of the control group (P&lt;0.021). The expressions of Fas and FasL were significantly downregulated by Carvedilol (P&lt;0.001 and 0.003, respectively). The caspase-3 activity and the content of MDA in the Carvedilol treated group was also significantly reduced (P&lt;0.026 and 0.005, respectively). Conclusions Carvedilol significantly reduces CPB-induced cardiomyocyte apoptosis in dog hearts and the reduction of cardiomyocyte apoptosis is associated with downregulation of Fas and FasL expression, inhibition of caspase-3 activity and oxidative stress in LV.     

Myocardial protection with pinacidil induced hyperpolarized arrest during cardiopulmonary bypass

Objective To investigate the myocardial protective effects of pinacidil-induced hyp erpolarized arrest and compare with those afforded by conventional dep olarized hyperkalemic arrest. Methods Eighteen dogs were equally divided into three groups: normothermic hyperpo larized group (Group A), hypothermic hyperpolarized group (Group B), and hyperk a lemic group (Group C). Pinacidil (50 μmol/L) containing 37℃ St . Thomas sol ution (K(+) 5 mmol/L, 10 ml/kg), pinacidil (50 μmol/L, Sigma, USA) containi ng 4℃ St. Thomas solution (K(+) 5 mmol/L, 10 ml/kg) and 4℃ standard St. Thomas solu tion (K(+) 16 mmol/L, 10 ml/kg) were infused respectively through the aortic r oot after aortic-clamping. Heart arrest and its recovery, ultrastruct ure of the myocardium, the level of serum myocardial enzymes, and lipid perox ide and adenine nucleotide of the myocardium were measured. Hemodynamics durin g ischemia and after reperfusion were observed.Results The percentages of normal mitochondria and glycogen did not change much du r ing ischemia (except at 60 min) and after reperfusion in B Group, but declin ed markedly in Group C 30 min and 60 min after ischemia and 20 min after repe rfusion (P&lt;0.01). In Group A, they were lower than those of Group B before ischemia, but higher than those of Group C. The recoveries of CO, SV, CI, LVSW, RVSW and MAP in Group B were significantly better than t hose in other two groups 15 min and 30 min after reperfusion (P&lt;0.05 and 0.01, respectively). However, they were still better in Group A tha n those in Group C (P&lt;0.05 and 0.01, respectively). The onset of he art arrest was faster in Groups C and B than that in Group A . Highly elevated serum myocardial enzymes were observed 60 min after ischem ia and 20 min after reperfusion in Group C, while they were only mild in the hy perpolarized groups, especially in Group B, and their recoveries were rapid. A denine nucleotides of the myocardium were better preserved in Group B than in other two groups 30 min, 60 min after ischemia, and 20 min after reperfusion ( P&lt;0.05 and 0.01, respectively). They were also much better in Gro up A than in Group C (P&lt;0.05 and 0.01, respectively). Lipid pero xide of the myocardium were significantly lower in Group B than in other grou ps 20 min after reperfusion (P&lt;0.01), and they were lower in Group A than in Group C (P&lt;0.05). Conclusions Myocardial protection for global ischemia during cardiopulmonary bypass (CPB) could be achieved with hyperpolarized heart arrest induced by pi nacidil, an ATP- sensitive potassium channel opener, especially in the hypothermic state. The protection is weaker in normothermia but is stil l superior to that with traditional depolarized hyperkalemic arrest.     

Comparative study of the effect of basic fibroblast growth factor and vascular endothelial growth factor on limb ischemia/reperfusion injury of rats

Objective To investigate the effect of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) on limb ischemia/reperfusion injury of rats and the mechanism. Methods The hind limb ischemia/reperfusion injury of male SD rats was induced by tourniquet for 2 hours and then reperfusing for 12 hours with administration of different agents. Animals were divided into control, bFGF-10 and bFGF-50, VEGF-10 and VEGF-50 group by infusing physiological saline, 10 and 50 μg/kg bFGE, 10 and 50 μg/kg VEGF, respectively. Blo od was collected to determine malonyldialdehyde (MDA), and the ischemic-reperfused gastrocnemius muscle and the contralateral control one were harvested together for measurement of tissue viability, water content, myeloperoxidose (MPO) activity, ATP and MDA concentration.Results Compared with control group, tissue viability of ischemia/reperfusion limb in bFGF-10 and bFGF-50 group increased by 16.0% (P&lt;0.05) and 32.8% (P&lt;0.01), ATP content increased by 14.8% and 35.6% (P&lt;0.01), and plasma MDA level decreased by 45.2% and 56.2% (P&lt;0.01). 10 μg/kg bFGF had no significant effect on tissue water content, MPO activity, MDA concentration of ischemia/reperfusion limb, while 50 μg/kg of bFGF lowered these values by 15.7%, 32.5% and 13.6% (P&lt;0.05) and 14.7% (P&lt;0.01), MPO activity augmented by 44.9% and 96.1% (P&lt;0.01), ATP content decreased by 13.1% (P&lt;0.05) and 33.3% (P&lt;0.01). Plasma and tissue MDA concentrations in VEGF-10 group had no significant changes (P&gt;0.05), while in VEGF-50 group, these values were elevated by 46.4% and 38.6% (P&lt;0.01) . Conclusion bFGF attenuated, while VEGF exacerbated ischemia/reperfusion injury of rat limb significantly, the mechanism of which was probably related to preventing or enhancing lipid peroxide, and increasing or decreasing energy store.     

雷米普利预适应对大鼠心脏延迟性的保护作用

目的探讨雷米普利预适应对大鼠离体心脏缺血-再灌注损伤的延迟性保护作用及机制。方法离体大鼠心脏采用Langendoff灌流法建立心肌缺血再灌注损伤模型。35只大鼠随机分为5组：（1）对照组；（2）缺血-再灌组（I／R组）；（3）雷米普利预处理组（Ramipril 0．05mg／kg）；（4）雷米普利预处理组（Ramipril 0．1mg／kg）：（5）HOE140＋雷米普利预处理组（HOE1400．1mg／kg＋Ramipril 0．1mg／kg）。每组7只。记录左室内压（LVP）、左室内压最大上升速率（＋dp／dtmax）、左室舒张末压（LVEDP）、心率（HR），定时收集冠脉流出液测量冠脉流量（CF）和肌酸激酶（CK）活性。再灌注结束后采用分光光度法测定心肌组织中丙二醛（MDA）含量。结果（1）与对照组比较，I／R组缺血-再灌注后10、20、30min可显著降低LVP和＋dp／dt max（P〈0.01），升高LVEDP（P〈0．01），降低CF（P〈0．01），缺血-再灌注后10、20min显著降低HR（P〈0．01）；（2）与I／R组比较，Ramipril 0．05mg／kg组缺血-再灌注后20、30min可显著升高LVP（P〈0．01）及增加CF（P〈0．05）；缺血-再灌注后10、20、30min可显著升高＋dp／dtmax（P〈0.01），降低LVEDP（P〈0.01）；（3）与I／R组比较，Ramipril 0．1mg／kg组缺血-再灌注后10、20、30min可显著升高LVP（P〈0．01），升高＋dp／dtmax（P〈0.01），降低LVEDP（P〈0.01）；增加CF（P〈0.05）；（4）与Ramipril 0．1mg／kg组比较，HOE1400．1mg／kg＋Ramipril 0．1mg／kg组缺血-再灌注后10、20、30min可显著降低LVP（P〈0.05）；降低＋dp／dtmax（P〈0．05）；升高LVEDP（P〈0.05）；降低CF（P〈0．05）；（5）I／R组缺血-再灌注后10、20、30minCK与对照组比较，均有显著性差异（P均〈0.01）；Ramipril 0．05mg／kg组及Ramipril 0．1mg／kg组缺血-再灌注后10、20、30minCK与I／R组比较，均有显著性差异（P均〈0.01）；HOE1400．1mg／kg＋Ramipril 0．1mg／kg组缺血-再灌注后10、20、30minCK与Ramipril 0．05mg／kg组及Ramipril 0．1mg／kg组比较，均有显著性差异（P均〈0.01）；（6）实验前24h舌下静脉注射雷米普利0．05mg／kg或0．1mg／kg均可显著降低缺血-再灌注心肌组织中MDA含量。结论雷米普利对缺血再灌注诱导离体大鼠心肌损伤具有延迟性保护作用，其机制可能是与激活缓激肽B2受体，减少缓激肽降解有关。     

银杏叶提取物的心肌延迟保护作用及其机制研究

目的观察银杏叶提取物(EGb761)对大鼠离体心脏心肌的延迟保护作用及其机制。方法离体大鼠心脏全心停灌缺血30min后再灌注30min产生缺血再灌损伤,观测心率(HR)、冠脉流量(CF)、左室内压(LVP)和左室内压变化最大速率( dp/dtmax),测定心肌组织中肌酸激酶(CK)释放量、心肌组织丙二醛(MDA)和一氧化氮(NO)的量。结果实验前24h单次ig给予EGb761(50或100mg/kg)可显著改善心肌缺血再灌注所致的心功能(LVP和 dp/dtmax)损伤,抑制心肌组织CK释放和MDA水平的增加以及NO水平的降低。预先给予NO合酶抑制剂L-NAME(5mg/kg)或心肌肌细胞膜ATP敏感钾通道(sarcKATP)阻断药HMR1883(3mg/kg),均可明显抑制EGb761对心肌缺血再灌注损伤的延迟保护作用。结论EGb761对缺血再灌注诱导大鼠心肌损伤具有延迟性保护作用,这一保护作用可能与增加NO合成和开放sarcKATP通道有关。     

参麦注射液对DPPH自由基所致兔离体心脏功能损伤的保护作用

目的：在兔离体灌流心脏观察参麦注射液对DPPH自由基所致心功能损伤的保护作用。方法：离体兔心采用Langendorff法灌流，记录左室内压(LYP)、左室内压上升速率( dp／dtmax)、左室舒张末压(LVEDP)、心率(HR)，定时收集冠脉流出液测量冠脉流量(CF)和肌酸激酶(CK)活性。结果：用含0．25μmol／L DPPH的K-H液灌流心脏10min，LVP， dp／dtmax明显降低，LVEDP升高，冠脉流量中的CK值明显增加。用含参麦注射液(1：320)的K-H液灌流心脏10min，可显著减轻DPPH所致的心功能损伤，减少CK的释放。结论：参麦注射液对DPPH自由基所致心功能损伤具有明显保护作用。     

地塞米松对缺血再灌注大鼠血流动力学和心肌超微结构的影响

目的:探讨地塞米松预处理对缺血再灌注大鼠血流动力学和心肌超微结构的影响.方法:将SD大鼠予地塞米松预处理,生理盐水预处理设为对照.预处理24 h后构建Langendorff离体心脏缺血再灌注动物模型,动态观测缺血前及再灌注期间血流动力学的改变;观察大鼠心肌超微结构及热休克蛋白72(HSP72)表达变化.结果:地塞米松预处理诱导大鼠心肌HSP72的表达较对照组显著增加(P＜0.05);地塞米松可改善再灌注期间血流动力学指标(左心室发展压、左心室收缩的最大速率、左心室舒张的最大速率、冠状动脉循环流出量,P＜0.01)及减轻缺血再灌注后心肌超微结构的损伤.结论:地塞米松预处理对缺血再灌注大鼠的心脏具有延迟保护作用.     

二氧化硫对大鼠离体灌注心脏心功能的影响

目的 观察二氧化硫(SO2)对大鼠离体心脏心功能的影响及可能的机制.方法 应用Langendorff大鼠离体心脏灌流模型,以不同浓度SO2供体(Na2SO3/NaHSO3)(1、10、100、1000μmoL/L)或0.5 μmol/L天冬氨酸异羟肟酸(HDX)灌流心脏5 min,并以生理浓度SO2供体(NA2SO3/NaHSO,)(10 μmol/L)持续灌流20 min,测量心率、左心室内压差(左心室收缩末压-舒张末压)、左心室内压变化速率(±dp/dtmax)以及冠脉流量;应用钙离子通道阻断剂尼卡地平预灌流后再给予生理剂量SO2供体(Na2SO3/NaHSO3)灌注,观察尼卡地平是否可以阻断SO2的心脏效应.结果 SO2呈浓度依赖性地抑制左心室±dp/dtmax、左心室内压差、心率以及冠脉流量(均P＜0.01);生理剂量SO2供体(Na2SO3/NaHSO3)持续灌流20 min,灌流20 min时,左心室内压差,+dp/dtmax、-dp/dtmax及心率分别为:(15±3)mm Hg(1 mm Hg=0.133 kPa),(485 ±74)mm Hg/s,(339 ±64)mm Hg/s,(114 ±26)次/min;均明显低于灌流5 min时的左心室内压差[(23±7)mm Hg]、+dp/dtmax[(595±93)mm Hg/s]、-dp/dtmax[(436±83)mm Hg/s]及心率[(159±31)次/min],均P＜0.05;0.5 μmol/L HDX灌注后左心室内压差降低,左心室±dp/dtmax减少、冠脉流量减少(P＜0.05或P＜0.01);尼卡地平可阻断生理剂量SO2对心功能的抑制效应.结论 外源性SO2对大鼠离体心脏的心功能具有负性肌力作用,其作用机理与电压门控钙通道有关.     

参麦注射液对DPPH自由基所致兔离体心脏功能损伤的保护作用

目的 :在兔离体灌流心脏观察参麦注射液对DPPH自由基所致心功能损伤的保护作用。方法 :离体兔心采用Langendorff法灌流 ,记录左室内压 (LVP)、左室内压上升速率 (+dp/dtmax)、左室舒张末压 (LVEDP)、心率(HR) ,定时收集冠脉流出液测量冠脉流量 (CF)和肌酸激酶 (CK)活性。结果 :用含 0 .2 5 μmol/LDPPH的K H液灌流心脏 1 0min ,LVP ,+dp/dtmax明显降低 ,LVEDP升高 ,冠脉流量中的CK值明显增加。用含参麦注射液(1 :32 0 )的K H液灌流心脏 1 0min ,可显著减轻DPPH所致的心功能损伤 ,减少CK的释放。结论 :参麦注射液对DPPH自由基所致心功能损伤具有明显保护作用     

肾上腺髓质素和肾上腺髓质素原N端20肽对大鼠离体灌流心脏功能的影响

目的 :研究肾上腺髓质素原 (proadrenomedullin ,proADM)的不同肽段 ,肾上腺髓质素 (adrenomedullin ,ADM )和肾上腺髓质素原N端 2 0肽 (proadrenomedullinN terminal 2 0 peptide ,PAMP)的心脏效应及可能机制。方法 :Langendorff装置灌流离体大鼠心脏 ,通过心室内的乳胶水囊经换能器连于PowerLab多导生理记录仪 ,观察不同浓度的ADM和PAMP对左心室内压 (leftventricularpressure ,LVP)、左室内压变化速率 (leftventricularpressure(dp/dtmax)、冠状动脉 (冠脉 )流量 (coronaryfluid ,CF)和心率 (heartrate,HR)的影响 ,并检测灌流后心肌组织cAMP含量。结果 :ADM (1 0 -1 1 ～ 1 0 -8mol·L-1 )灌流呈浓度依赖地降低心脏LVP和±dp/dtmax ;PAMP也以浓度依赖的方式降低上述心功能的指标 ,且较相同浓度的ADM作用强。PAMP与ADM依次以不同浓度梯度联合应用 ,较各药单用对上述心功能指标的影响表现为低浓度 (1 0 -1 1 ～ 1 0 -1 0 mol·L-1 )时增强 ,而高浓度 (1 0 -9～ 1 0 -8mol·L-1 )削弱其心功能抑制效应。ADM和PAMP单独或联合应用时 ,冠脉流量均高于对照组水平。灌流液含有NO合酶 (nitricoxidesynthase ,NOS)抑制剂L NAME(Nω nitro L argininemethylester)时 ,ADM、PAMP或ADM联合PAMP灌流 ,其对LVP、±dp     

κ-阿片受体的负性肌力作用及其对β-肾上腺素受体的调节

目的研究U50, 488H（选择性κ-阿片受体激动剂）对心脏的负性肌力作用特点及对β-肾上腺素受体（β-AR）的调节作用. 方法①整体动物实验，观察U50, 488H对家兔心率（HR）、动脉压（ABP）、左心室内压（LVP）及其微分（±dp/dtmax）的影响；②利用Langerdoff装置离体灌流大鼠心脏，观察U50, 488H对HR，LVP和±dp/dtmax及β- AR正性肌力作用的影响. 结果①U50, 488H可显著降低家兔的HR，ABP，LVP及±dp/d tmax；②U50, 488H对离体大鼠心脏的HR, ABP, LVP及±dp/dtmax有降低作用；③在U50, 488H 存在的情况下，激动β-AR所引起的LVP的升高可被显著抑制. 结论①U50, 488 H对心脏具有负性肌力作用；②U50,488H可抑制β-AR的正性肌力作用，提示κ-阿片受体对β- AR具有负性调节作用.     

茶多酚改善大鼠缺血/再灌注心脏功能和能量代谢并抑制体外培养心肌细胞的钙内流

目的：探讨茶多酚对缺血/再灌注心脏损伤的保护作用,并研究心脏能量代谢和心肌细胞钙内流是否参与了心脏缺血/再灌注损伤的保护作用。方法在大鼠Langendorff离体心脏上实施缺血/再灌注各30 min,用一导管经压力换能器连接放大器记录心功能指标;用31P NMR技术测定心脏的能量代谢,全细胞膜片钳技术记录心肌细胞钙内流。结果与对照组比较,茶多酚（2.5 mg/L）能使缺血/再灌注心脏的心室发展压、左心室压最大收缩速率（+dp/dtmax）、左心室压最大舒张速率（-dp/dtmax）和冠脉流量显著增加（P<0.05）,并显著改善缺血/再灌注心脏的能量代谢,增加心肌ATP和PCr含量（P<0.05）。浓度为2.5和5.0 mg/L的茶多酚均能显著抑制培养心肌细胞的钙内流（P<0.01）。结论茶多酚对大鼠离体心脏缺血/再灌注损伤的保护作用可能与其改善心肌能量代谢、抑制心肌细胞钙内流的作用有关。     

左旋卡尼汀后处理联合预处理对离体大鼠心肌缺血再灌注损伤作用的研究

目的评价左旋卡尼汀（L-CN）对离体大鼠急性心肌缺血再灌注损伤的保护作用并比较预处理与后处理及预处理联合后处理保护作用的区别。方法动物心脏随机分为对照组、缺血后处理组、L-CN后处理组、L-CN预处理组和联合处理组。左旋卡尼汀分别于缺血后、缺血前或缺血前后给予10 min。检测心率（HR）、冠脉流量（CF）和不同时间点冠脉收集液中肌酸激酶（CK）、乳酸脱氢酶（LDH）含量,并测定心肌梗死区与风险区的比例。结果各组CK,LDH,CF,HR及心肌风险区在灌注前均无明显差异（P〉0.05）,复灌60 min时,各项指标在各处理组与对照组之间有明显差异,各处理组之间无显著差异,而CF在复灌120 min时,、L-CN后处理组与其他处理组相比P〈0.05。各组心肌梗死范围在心肌风险区无明显差别。结论左旋卡尼汀预处理、后处理及二者联合对离体大鼠心肌均有保护作用,预处理及后处理与二者联合的保护作用无显著差异。