The effect of an Na+/H+ exchange inhibitor, SM-20550, on ischemia/reperfusion-induced endothelial dysfunction in isolated perfused rat hearts

The aim of this study was to test the protective effect of an Na+/H+ exchange (NHE) inhibitor, SM-20550, on ischemia/reperfusion-induced endothelial dysfunction. Isolated rat hearts were subjected to 30 min of global ischemia followed by 20 min of reperfusion and their responses to the endothelial-dependent vasodilator, acetylcholine, and the endothelial-independent vasodilator, nitroglycerin, before and after ischemia were examined. Acetylcholine-induced relaxation was impaired after ischemia/reperfusion while nitroglycerin induced relaxation was not. Administration of 1-10 nmol/l SM-20550 [N-(aminoiminomethyl)-1,4-dimethyl-1H-indole-2-carboxamide methanesulfonic acid] before and after ischemia prevented impairment of acetylcholine-induced relaxation. To further understand the mechanism of SM-20550 in protecting endothelial function, we measured the inhibitory activity of SM-20550 on NHE in cultured endothelial cells. SM-20550 (1-100 nmol/l) inhibited recovery from acidosis induced by an NH4Cl prepulse in a concentration-dependent manner. Oxygen radicals from endothelial cells and leukocytes are one of the major sources of endothelial cell injury during ischemia and reperfusion. Consequently, we tested the effect of SM-20550 on H2O2-induced endothelial cell injury. SM-20550 (100-1,000 nmol/l) prevented H2O2-induced cell injury measured by lactate dehydrogenase assay. In conclusion, SM-20550 inhibited NHE in endothelial cells, protected ischemia/reperfusion-induced endothelial dysfunction and prevented H2O2-induced endothelial cell injury at higher concentrations.     

Na+/H+ exchange inhibitor reduces vascular injury caused by ischemia-reperfusion in the rat hind limb

This study was designed to evaluate the effects of an Na+/H+ exchange inhibitor, SM-20550, on ischemia-reperfusion injury in the skeletal muscle. Male Sprague-Dawley rats were exposed to ischemia and reperfusion by clamping and releasing clamps both at the abdominal aorta and the bilateral femoral arteries. Rats were divided into three groups; the sham, the SM-20550 treated (SM), and the untreated control (Control) groups. In the SM and control groups, rats were exposed to 5-hr ischemia and 5-hr reperfusion. In the sham group, vessel isolation only was performed. SM-20550 (2.8 mg/kg/hr) in the SM group or vehicle in the sham and control group was continuously administered during ischemia and reperfusion periods. The wall thickness of the vessels were significantly (p<0.01) decreased in the control group than any other group. The internal diameter was significantly (p<0.01) higher in the control and SM group than in the sham group. The wall thickness/internal diameter ratio was significantly (p<0.05) lower in the control group than in the SM group. Thus, an Na+/H+ exchange inhibitor, SM-20550, ameliorated the morphological change due to ischemia reperfusion. These findings provide a clue into the mechanism of ischemia reperfusion injury.     

缝隙连接脱耦联剂庚醇对大鼠缺血-再灌注损伤心肌的保护作用

目的：在整体大鼠心脏缺血-再灌注损伤模型上研究庚醇的心肌保护作用，并在离体缺氧心脏模型上观察庚醇对电耦联参数的影响。方法：在体大鼠实验模型，结扎冠状动脉左前降支30 min和复灌2 h，观察不同剂量的庚醇（0.03、0.06、0.30和0.60 mg/kg）的作用；离体大鼠实验模型，全心停灌70 min，应用四电极法观察不同浓度的庚醇（0.05、0.10、0.50和1.00 mmol/L）对缺氧期间心肌整体阻抗和电脱耦联参数的影响。结果：庚醇对在体大鼠缺血-再灌注损伤心肌具有减少心律失常发生和缩小心肌梗死面积的作用；各浓度庚醇（0.05-1.00 mmol/L）均明显延迟心肌缺氧期间电脱耦联时间和平台时间，降低电脱耦联最大速率。结论：适度剂量的庚醇对在体缺血-再灌注损伤心肌有保护作用，其作用可能与其引起的电脱耦联延迟有关。     

Protective effect of sauchinone against regional myocardial ischemia/reperfusion injury: inhibition of p38 MAPK and JNK death signaling pathways

Sauchinone has been known to have anti-inflammatory and antioxidant effects. We determined whether sauchinone is beneficial in regional myocardial ischemia/reperfusion (I/R) injury. Rats were subjected to 20 min occlusion of the left anterior descending coronary artery, followed by 2 hr reperfusion. Sauchinone (10 mg/kg) was administered intraperitoneally 30 min before the onset of ischemia. The infarct size was measured 2 hr after resuming the perfusion. The expression of cell death kinases (p38 and JNK) and reperfusion injury salvage kinases (phosphatidylinositol-3-OH kinases-Akt, extra-cellular signal-regulated kinases [ERK1/2])/glycogen synthase kinase (GSK)-3β was determined 5 min after resuming the perfusion. Sauchinone significantly reduced the infarct size (29.0% ± 5.3% in the sauchinone group vs 44.4% ± 6.1% in the control, P < 0.05). Accordingly, the phosphorylation of JNK and p38 was significantly attenuated, while that of ERK1/2, Akt and GSK-3β was not affected. It is suggested that sauchinone protects against regional myocardial I/R injury through inhibition of phosphorylation of p38 and JNK death signaling pathways.     

Cardioprotection of SM-15681, an Na+/H+ exchange inhibitor in ischemic and hypoxic isolated perfused rat hearts

We investigated the effects of SM-15681 (N-(aminoiminomethyl)-1-methyl-1H-indole-2-carboxamide monohydrochloride) on Na+/H+ exchange activity in the myocardium and in ischemic and hypoxic injury in isolated perfused rat hearts. These effects were compared with those of ethylisopropyl amiloride (EIPA). Na+/H+ exchange activity was studied with a NH4Cl prepulse technique under HCO3(-)-free conditions. SM-15681 (10(-8)-10(-7) M) inhibited pH recovery of acidosis in the rat myocardium in a concentration-dependent manner and the IC50 value of SM-15681 (80 nM) was similar to that of EIPA. In perfused rat hearts, SM-15681 (10(-6) M) and EIPA (10(-6) M) significantly improved cardiac functions and prevented enzyme release and abnormal elevation of tissue Ca2+ content during 20 min of reperfusion after 40 min of ischemia and 20 min of reoxygenation after 30 min of hypoxia. We conclude that an Na+/H+ exchange inhibitor, SM-15681, shows cardioprotective effects on ischemia/reperfusion and hypoxia/reoxygenation injury. Our results also support the hypothesis that Na+/H+ exchange contributes to the pathophysiology of cardiac ischemic reperfusion injury.     

Delayed treatment of Na+/H+ exchange inhibitor SM-20220 reduces infarct size in both transient and permanent middle cerebral artery occlusion in rats

SM-20220 (N-(aminoiminomethyl)-1-methyl-1H-indole-2-carboxamide methanesulfonate) is a Na+/H+ exchanger (NHE) inhibitor which has been shown to attenuate cerebral edema in the rat transient focal ischemia model. However, to date, the effect of SM-20220 on cerebral infarction has not been examined. The present experiments were designed to investigate these effects, using both transient and permanent middle cerebral artery (MCA) occlusion models in rats. A dose of 1 mg/kg given intravenously 30 min after the onset of transient MCA occlusion reduced the infarcted area. In the permanent MCA occlusion model, SM-20220 reduced the infarcted area when treatment was delayed for 5, 30 or 60 min after the onset of ischemia. The present results show that NHE has a crucial role in the pathogenesis of ischemic brain damage. This NHE inhibitor may be useful for treating stroke because of its effectiveness with both forms of ischemia and because of its postischemic administration.     

Differential activation of protein kinase C between ischemic and pharmacological preconditioning in the rabbit heart

The objective of the present study was to investigate the differential activation of protein kinase C between ischemic (IPC) and pharmacological preconditioning (PPC) in the rabbit heart. Control, IPC, diazoxide (Diaz), and chelerythrine (Chel)+IPC groups underwent prolonged coronary artery occlusion (CAO) for 30 minutes followed by 180 minutes' reperfusion (protocol I). In protocol II, sham, IPC-only, Diaz-only, and Chel+IPC-only groups did not undergo prolonged CAO. IPC was induced with 4 cycles of 5-min regional ischemia and 10-min reperfusion before prolonged CAO. Diaz (5 mg/kg) was administered 30 min before prolonged CAO. Chel (5 mg/kg) was administered 5 min before the IPC procedure. Infarct size was determined by tetrazolium staining. Assessment of protein kinase C (PKC) isoforms from a left ventricular (LV) sample was conducted by western blotting. Apoptosis in situ was determined by TUNEL assay. The infarction area in the IPC (11.6 +/- 1.0%) and Diaz (19.5 +/- 3.8%) groups was reduced significantly (p< 0.01, p< 0.05) relative to the control group (40.0 +/- 3.8%). The reduction by IPC was abolished by pretreatment with Chel. Apoptosis was significantly decreased (p< 0.01) in the IPC and diazoxide groups compared with the control and Chel+IPC groups (control: 4.78 +/- 0.56% vs. IPC: 2.00 +/- 0.38% vs. Diaz: 2.20 +/- 0.32% vs. Chel+IPC: 4.32 +/- 0.41%) and DNA laddering was attenuated in the IPC and Diaz groups. Membrane PKC-epsilon levels in the IPC and Diaz groups increased significantly relative to the control and Chel+IPC groups. Membrane PKC-epsilon levels in the IPC-only group showed greater increases than the Diaz-only and Chel+IPC-only groups. These findings suggest that whereas PPC suppresses apoptosis when diazoxide opens mitochondrial K(ATP) channels and then activates PKC-epsilon through ischemia-reperfusion, IPC activates PKC-epsilon in the particulate fraction prior to continuous ischemia-reperfusion. We concluded that the difference between IPC and PPC appears to consist in the difference in the timing of PKC-epsilon activation, though both IPC and PPC provide the cardioprotection in ischemia-reperfusion injury.     

Anandamide content is increased and CB1 cannabinoid receptor blockade is protective during transient, focal cerebral ischemia

The role of endocannabinoid signaling in the response of the brain to injury is tantalizing but not clear. In this study, transient middle cerebral artery occlusion (MCAo) was used to produce ischemia/reperfusion injury. Brain content of N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol were determined during MCAo. Whole brain AEA content was significantly increased after 30, 60 and 120 min MCAo compared with sham-operated brain. The increase in AEA was localized to the ischemic hemisphere after 30 min MCAo, but at 60 and 120 min, was also increased in the contralateral hemisphere. 2-Arachidonoylglycerol content was unaffected by MCAo. In a second set of studies, injury was assessed 24 h after 2 h MCAo. Rats administered a single dose (3 mg/kg) of the cannabinoid receptor type 1 (CB1) receptor antagonist SR141716 prior to MCAo exhibited a 50% reduction in infarct volume and a 40% improvement in neurological function compared with vehicle control. A second CB1 receptor antagonist, LY320135 (6 mg/kg), also significantly improved neurological function. The CB1 receptor agonist, WIN 55212-2 (0.1-1 mg/kg) did not affect either infarct volume or neurological score.     

丝裂原活化蛋白激酶p38的激活在四逆汤预处理诱导大鼠心肌延迟预适应中的作用

目的：探讨四逆汤能否诱导心肌延迟预适应及其机制。 方法： SD大鼠分为正常对照组、假手术组、缺血再灌注(I/R）组、延迟缺血预处理组、四逆汤预处理组。延迟缺血预处理组采用经典大鼠冠脉结扎，缺血5 min，再灌5 min，反复循环3次，24 h后缺血1 h，再灌1 h。四逆汤预处理组给予四逆汤灌胃(5 mL·kg-1·d-1)连续3 d，末次灌药24 h后缺血1 h，再灌1 h。以心肌梗死面积、心肌酶为评价指标，测定心肌中NO2-/NO3-的含量并通过免疫组化检测大鼠心肌p38 MAPK及PKC的表达。 结果： 延迟缺血预处理组及四逆汤预处理组心肌梗死面积、血清CK、LDH的值明显少于I/R组，NO2-/NO3-含量显著高于I/R组，p38 MAPK和PKC发生转位且蛋白表达明显高于I/R组。 结论： 四逆汤能诱导心肌延迟预适应，其机制与p38 MAPK的激活可能有关。     

缺血预处理对肝硬化大鼠肝脏缺血再灌注中肝细胞凋亡的影响

目的:探讨缺血预处理(IPC)在肝硬化大鼠肝缺血再灌注(I/R)损伤的拮抗作用及其机理。方法:Pringle法复制肝I/R模型,将肝硬化大鼠随机分为3组:A组:肝缺血前给予1个IPC处理(缺血5min,灌注5min);B组:肝缺血前给予1个IPC处理(缺血10min,灌注10min);C组:对照组,单纯肝门血流阻断。肝缺血时间为30min,再灌注6h。测定各组的血清谷丙转氨酶(ALT)、肝组织Fas-mRNA表达、caspase-3活性和肝细胞凋亡。结果:经IPC处理后,大鼠7d生存率为100%,而无IPC处理组即为62.5%。再灌注6h,A、B2组的ALT明显低于C组,P＜0.01,A组的ALT亦明显低于B组,P＜0.01。检测A、C2组的肝组织Fas-mRNA表达、caspase-3活性和肝细胞凋亡发现,A组的上述指标均比C组低,P＜0.01。结论:IPC对肝硬化大鼠肝I/R损伤有显著的对抗作用,其中以缺血5min和灌注5min的IPC的作用较强。IPC的保护机理是通过下调Fas-mRNA的表达、抑制caspase-3活性,从而减少肝细胞凋亡来实现的。     

Hepatic ischemic preconditioning provides protection against distant renal ischemia and reperfusion injury in mice

We previously demonstrated that there are acute and delayed phases of renal protection against renal ischemia and reperfusion (IR) injury with renal ischemic preconditioning (IPC). This study assessed whether hepatic IPC could also reduce distant renal IR injury through the blood stream-mediated supply of reactive oxygen species (ROS). Male C57BL/6 mice were randomly divided into four groups: group I, sham operated including right nephrectomy; group II (IR), left renal ischemia for 30 min and reperfusion injury; group III (IPC-IR), hepatic ischemia for 10 min followed by 10 min of reperfusion before left renal IR injury; group IV (MPG - IPC + IR), pretreated with 100 mg/kg N-(2-mercaptopropionyl)-glycine (MPG) 15 min before hepatic IPC and left renal IR injury. Renal function, histopathologic findings, proinflammatory cytokines, and cytoprotective proteins were evaluated 15 min or 24 hr after reperfusion. Hepatic IPC attenuated the expression of proinflammatory cytokines, tumor necrosis factor α, intercellular adhesion molecule 1, and induced inducible nitric-oxide synthase, and the phosphorylation of Akt in the murine kidney. Renal function was better preserved in mice with hepatic IPC (group III) than groups II or IV. Hepatic IPC protects against distant renal IR injury through the blood stream-delivery of hepatic IPC-induced ROS, by inducing cytoprotective proteins, and by inhibiting inflammatory reactions.     

Gene transfer of the pancaspase inhibitor P35 reduces myocardial infarct size and improves cardiac function

Myocardial infarction and subsequent reperfusion lead to the activation of apoptosis, and the final destruction of the cell. The aim of this study was to show that broad-scale inhibition of caspases, the main executioners of apoptosis, improves functional outcome after ischemia and reperfusion in an in vivo model. Twenty male Wistar rats were directly injected with an adenovirus, encoding the baculoviral protein p35. Nineteen rats served as controls, and were injected with a virus only encoding green fluorescent protein (GFP). After 3 days, 12 animals were used for Langendorff perfusion experiments, the other 27 animals were submitted to in vivo infarction. Myocardial infarction was induced by ligation of the left anterior descending artery (LAD) for 30 min, and reperfusion for 24 h. Echocardiographic and hemodynamic measurements were made 24 h after infarction. Infarct size was assessed in all animals histologically. In both, in vivo and Langendorff perfused hearts, myocardial infarct size was significantly reduced in the p35 group (for in vivo experiments: 0.11+/-0.03 vs 0.33+/-0.03 in the GFP group, p<0.01), as was the ratio of infarct size to area at risk (6 vs 17%, p<0.01). Left ventricular function was similar in both groups prior to infarction, but was significantly less compromised after infarction in the p35 group. The left ventricular systolic pressure after infarction was higher in the p35 group (107+/-5 vs 92+/-4 mmHg, p<0.05), as was the maximal rate of rise of left ventricular systolic pressure dp/dt (5,659+/-585 vs 4,634+/-256 mmHg s(-1), p<0.05). Adenoviral gene transfer of the caspase inhibitor p35 leads to a significant reduction of the myocardial infarct size after ischemia and reperfusion. Hemodynamic variables were significantly improved by treatment with p35. Cardiac restricted inhibition of apoptosis seems to be a promising approach for ameliorating the effects of ischemia and reperfusion.     

Does nitric oxide generation contribute to the mechanism of remote ischemic preconditioning?

The protective effect of local or remote ischemic preconditioning (IPC) on subsequent 40-min ischemic and 120-min reperfusion myocardial damage was investigated. Preconditioned rats underwent one cycle of myocardial ischemia/reperfusion consisting of 5-min ischemia produced as a left coronary artery (LCA) occlusion and 5 min of reperfusion. Remote IPC was produced as 15 min of small intestinal ischemia with 15 min of reperfusion as well as 30 min of limb ischemia with 15 min of reperfusion. A marked protective action was afforded by both IPC protocols with a more significant effect of local (classic) ischemic preconditioning. Since the protective effect of remote IPC was not abolished by nitric oxide (NO) synthase inhibition with Nω-nitro- -arginine ( -NNA) it is concluded that NO generation may not be involved in the mechanism of remote IPC.     

Post-ischemic delivery of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor rosuvastatin protects against focal cerebral ischemia in mice via inhibition of extracellular-regulated kinase-1/-2

After recent clinical trials, statins have gained increasing significance in secondary stroke prevention. From experimental studies, it is well established that statins have beneficial action when delivered prophylactically prior to a stroke. Conversely, much less is known about the effects of statins on injury development when delivered after ischemia. We here examined the effects of a post-ischemic delivery of rosuvastatin (0.5, 5 or 20 mg/kg, administered i.p. immediately after reperfusion onset), a potent 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on brain injury and cell signaling after focal cerebral ischemia, induced by 90 min of intraluminal middle cerebral artery occlusion in mice. In animals receiving normal saline, 0.5 or 5 mg/kg rosuvastatin, middle cerebral artery occlusions resulted in reproducible brain infarcts at 24 h after reperfusion onset, which did not differ in size. However, rosuvastatin, administered at higher doses (20 mg/kg), reduced infarct volume at 24 and 48 h after ischemia (by 34+/-16% and 18+/-3%, respectively, P<0.05). Western blots revealed that rosuvastatin decreased phosphorylated extracellular-regulated kinase-1/-2 and reduced activated caspase-3 levels in ischemic brain areas, while endothelial NO synthase expression, p38 and Jun kinase phosphorylation were not influenced by the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor. Rosuvastatin also significantly diminished expression levels of inducible NO synthase in the ischemic brain. Our results indicate that rosuvastatin may have utility not only as stroke prophylaxis but also as acute therapy inhibiting executive cell death pathways.     

Cardiac sodium/calcium exchanger preconditioning promotes anti-arrhythmic and cardioprotective effects through mitochondrial calcium-activated potassium channel

Background: Reverse-mode of the Na⁺/Ca²⁺ exchanger (NCX) stimulation provides cardioprotective effects for the ischemic/reperfused heart during ischemic preconditioning (IP). This study was designed to test the hypothesis that pretreatment with an inhibitor of cardiac delayed-rectifying K⁺ channel (I_Kr), E4031, increases reverse-mode of NCX activity, and triggers preconditioning against infarct size (IS) and arrhythmias caused by ischemia/reperfusion injury through mitoK_Ca channels. Materials and methods: In the isolated perfused rat heart, myocardial ischemia/reperfusion injury was created by occlusion of the left anterior descending coronary artery for 30 min followed by 120 min reperfusion. Two cycles of coronary occlusion for 5 min and reperfusion were performed, or pretreatment with E4031 or sevoflurane (Sevo) before the 30 min occlusion with the reversed-mode of NCX inhibitor (KB-R7943) or not. Results: E4031 or Sevo preconditioning not only markedly decreased IS but also reduced arrhythmias, which was significantly blunted by KB-R7943. Furthermore, these effects of E4031 preconditioning on IS and arrhythmias were abolished by inhibition of the mitoK_Ca channels. Similarly, pretreatment with NS1619, an opener of the mitoK_Ca channels, for 10 min before occlusion reduced both the infarct size and arrhythmias caused by ischemia/reperfusion. However, these effects weren’t affected by blockade of the NCX with KB-R7943. Conclusion: Taken together, these preliminary results conclude that pretreatment with E4031 reduces infarct size and produces anti-arrhythmic effect via stimulating the reverse-mode NCX, and that the mitoK_Ca channels mediate the protective effects.     

Infarct size-limiting effect of calcium preconditioning in rabbit hearts

Recent studies demonstrated that brief period of Ca2+ depletion and repletion (Ca2+ preconditioning, CPC) has strong protective effects against ischemia in a rat heart. CPC and classic preconditioning (IPC) were compared in relation with infarct size and protein kinase C (PKC) isozymes. Isolated Langendorff-perfused rabbit hearts were subjected to 45-min ischemia (Isc) followed by 120-min reperfusion (R) with or without IPC, induced by 5-min Isc and 10-min R. In the CPC hearts, 5-min Ca2+ depletion and 10-min repletion (CPC) were given before 45-min Isc, with or without concurrent PKC inhibition (calphostin C, 200 nmol/L). IPC enhanced recovery of LV function, while CPC did not. Infarct size was significantly reduced by both CPC and IPC (p < 0.05 vs. ischemic control). Membrane PKC was significantly increased from 2.53 +/- 0.07 (baseline, nmol/g tissue) to 3.11+/-0.07, 3.34 +/- 0.11, 3.15 +/- 0.09, and 3.06 +/- 0.08 by IPC, IPC and 45-min Isc, CPC and 45-min Isc, respectively (p < 0.01). Immunoblots of membrane PKC were increased by IPC, IPC and 45-min Isc, and CPC. These effects were abolished by PKC inhibition. Thus, activation of PKC may have trigger role in the mechanism of cardioprotective effect by CPC.     

丹参酮ⅡA预处理对大鼠心肌缺血再灌注损伤的作用研究

目的探讨丹参酮ⅡA对大鼠心肌缺血再灌注损伤的作用。方法雄性SD大鼠随机分为假手术组、模型组、丹参酮ⅡA预处理组,后两组进行冠状动脉左前降支结扎30min后再灌注120min。期间全程监测心率和血流动力学指标。实验结束后取心脏做Trc染色及HE染色,观察心肌梗死面积和组织学改变。结果模型组大鼠心脏功能明显下降并发生心肌梗死提示造模成功。与模型组比较,丹参酮ⅡA组在缺血30min,再灌注30、60、120min各时间点,左心室收缩末压、左室内压最大上升及下降速率明显增高、心率基本恢复正常。组织学染色显示,与模型组比较,丹参酮ⅡA组心肌梗死区面积降低、心肌细胞变性坏死程度明显减轻。结论丹参酮ⅡA预处理对大鼠心肌缺血再灌注损伤具有保护作用。     

Decrease of the electroacupuncture-induced analgesic effects in nuclear factor-kappa B1 knockout mice

We investigated whether pre-treatment with melatonin, a potent free radical scavenger and antioxidant, would protect against permanent focal cerebral ischemia without reperfusion in a rat middle cerebral artery occlusion (MCAO) model. A single dose of melatonin at 5, 15, or 50 mg/kg or the vehicle alone was given via an intraperitoneal injection at 0.5 h before permanent MCAO. Relative infarction volumes on day 3 were significantly reduced in the groups treated with melatonin at 5 (mean+/-SEM, 17.0+/-6.5%), 15 (18.1+/-5.8%), or 50 (20.6+/-5.0%) mg/kg when compared with the vehicle-treated group (37.1+/-2.8%) and so melatonin treatment achieved a relative reduction in infarct volume by 54.2, 51.2 and 44.5%, respectively. Melatonin did not affect the hemodynamic parameters. Thus, pre-treatment with melatonin at a dose between 5 and 50 mg/kg protects against focal cerebral ischemia without reperfusion.     

Involvement of reactive oxygen species in cardiac preconditioning in rats

To date, the involvement of reactive oxygen species in ischemic preconditioning in vivo in rats is not clearly demonstrated. The aim of the present study was to determine whether N-(2-mercaptopropionyl)glycine (MPG), a cell-diffusible hydroxyl radical scavenger, and carnosine, a potent singlet oxygen quencher, could block protection afforded by a single cycle of ischemic preconditioning in vivo in the rat. An ESR study was first performed to validate in vitro the specific antioxidant properties of carnosine and MPG. In a second set of experiments, open-chest rats were subjected to 30 min of left coronary occlusion followed by 60 min of reperfusion. Preconditioning was elicited by 5 min of ischemia and 5 min of reperfusion. Neither MPG (1-h infusion, 20 mg/kg) nor carnosine injection (bolus, 25 micro mol/rat) affected infarct size. The infarct size-limiting effect of preconditioning was completely blunted by MPG, whereas carnosine did not alter the cardioprotection. It is concluded that free radicals and especially hydroxyl radicals could be involved in the adaptive mechanisms induced by a single cycle of preconditioning in vivo in rats.     

尼可地尔激活RISK通路减轻高胆固醇大鼠心肌缺血/再灌注损伤

目的探讨尼可地尔对高胆固醇大鼠心肌缺血/再灌注损伤的影响及其可能机制。方法应用高胆固醇饮食喂养健康雄性Wistar大鼠8周建立高胆固醇大鼠模型,应用Langendorff灌流装置采用全心缺血30min和再灌注120min建立离体心脏缺血/再灌注(I/R)模型。在缺血前或再灌注即刻灌注含有尼可地尔的KH液10min以制备尼可地尔药物预处理(NIC-pre)与后处理(NIC-post)模型。通过TTC染色测量心肌梗死面积、TUNEL染色检测心肌细胞凋亡率,Western blot检测RISK通路p-Akt和p-Erk1/2蛋白表达水平。结果与I/R对照组相比,NIC-30pre组与NIC-30post组均可降低心肌梗死面积和心肌细胞凋亡率,并显著上调p-Akt和pErk1/2的表达水平。结论尼可地尔减轻高胆固醇大鼠心肌缺血/再灌注损伤,与其激活RISK通路相关。