内源性儿茶酚胺参与白细胞介素-2对大鼠离体心脏的作用

目的: 研究内源性儿茶酚胺是否参与白细胞介素-2(IL-2)的心脏作用.方法: 采用Langendorff离体心脏灌流模型,观察室性早搏次数、左室发展压(LVDP)、左室舒张末压(LVEDP)、心率(HR)和冠脉流量(CF)的变化.结果: ①50 U/ml IL-2增加离体心脏的室性早搏次数,增加LVDP、LVEDP、HR和CF.②利舍平(reserpine)或普萘洛尔(propranolol)预处理后,50 U/ml IL-2对离体心脏的作用消失;phentolamine预处理后,不改变50U/ml IL-2的离体心脏作用.③200 U/ml IL-2增加离体心脏的室性早搏次数,对LVDP、LVEDP、HR和CF无显著增加作用.④reserpine或propranolol预处理后,200 U/ml IL-2增加离体心脏的室性早搏次数作用不明显,LVDP、HR和CF降低、LVEDP增高.结论: 内源性儿茶酚胺介导了IL-2的致离体心脏心律失常、正性变时和变力作用,较高浓度的IL-2抑制离体心脏的功能.     

白细胞介素-2对心脏节律的作用及其机制的研究

目的：探讨白细胞介素－2（1L－2）对心脏节律作用及其可能机制。方法：采用体外培养乳鼠心肌细胞模型和离体人鼠灌流心脏模型,观察培养的心肌细胞搏动频率和离体心脏心率及节律。结果：①2.5-200u/ml的IL－2呈浓度依赖性地降低心肌细胞的搏动频率。②50u/ml的IL-2明显增加离体心脏心率和室性早搏个数。③propranolol预处理可取消50u/mlIL-2的离体心脏作用。④热失活IL－2对培养的心肌细胞搏动频率和离体心脏心率和心律都无显著作用。结论：IL－2可直接制培养心肌自律性,其对离体心脏的正性变时和致心律失常作用可能由内源性作茶酚胺介导。     

过氧化氢加重铁对心肌的损伤作用及其机制

采用Langendorff灌流心脏和酶解分离的心肌细胞为实验模型,研究铁对心肌的损伤作用,以及过氧化氢对铁的心肌作用的影响及其可能机制.结果显示(1)羟基喹啉铁复合物(Fe-HQ)引起分离心肌细胞舒张期缩短,心肌细胞的收缩幅度和速度降低,离体灌流心脏左室发展压(LVDP)、±dp/dtmax、心率、冠脉流量呈现双相变化;冠脉流出液中乳酸脱氢酶(LDH)、肌酸激酶(CK)释放量和心肌丙二醛(MDA)增高.(2)H2O2可加重Fe-HQ对心脏的损伤,冠脉流出液中LDH、CK释放量和心肌MDA增高,而LVDP、±dp/dtmax和心率明显降低.(3)还原型谷胱甘肽可对抗Fe-HQ+H2O2对心肌的损伤作用,DMSO对Fe-HQ+H2O2致离体心脏损伤无明显作用.结果提示,心肌细胞内铁增加可引起心肌功能受损,H2O2可加重铁对心肌的损伤作用,其主要机制可能与@OH无关,而主要与含巯基的蛋白质受损有关.     

一氧化氮在铁诱导的大鼠心肌损伤中的作用

采用Langendorff灌流大鼠心脏和酶解分离的心肌细胞为实验模型,研究铁负荷下心肌损伤情况以及一氧化氮（NO）在铁诱导的心肌损伤中的地位。结果显示:（1）心肌铁负荷（Fe-HQ）可使分离心肌细胞舒张期细胞长度缩短、收缩幅度和速度降低,离体灌流心脏左室发展压（LVDP）、±dp/dtmax、冠脉流量呈现双相变化;冠脉流出液中乳酸脱氢酶（LDH）、肌酸激酶（CK）释放量和心肌丙二醛（MDA）增高。（2）NO的前体L-精氨酸（L-argi-nine,L-Arg）引起心肌细胞舒张期细胞长度缩短、收缩幅度降低。离体灌流心脏LVDP、冠脉流量、和±dp/dtmax增高,用K-H液复灌后可恢复正常。（3）L-Arg预处理,再行Fe-HQ灌流,与单纯的L-Arg或Fe-HQ组相比,心肌细胞舒张期细胞长度、收缩幅度和速度减小;离体灌流心脏LVDP、±dp/dtmax、心率和冠脉流量明显下降,冠脉流出液中LDH、CK增加。（4）Nω-硝基-L-精氨酸甲酯（L-NAME）和Fe-HQ合并灌流后,与单纯Fe-HQ组相比,心肌细胞舒张期细胞长度、收缩幅度和速度增加。L-NAME可阻断Fe-HQ引起的LVDP、左室舒张末压（LVEDP）和±dp/dtmax降低,冠脉流出液中LDH、CK增高。（5）用Triton X-100短暂处理以去除冠脉内皮后,与保留冠脉内皮的心肌相比,Fe-HQ引起的LVDP和±dp/dtmax的一过性增高现象被抑制,但     

线粒体钙单向转运体在心肌低氧/复氧损伤中的作用

目的:观察线粒体钙单向转运体在心肌低氧/复氧损伤中的作用并探讨其机制。方法:应用Langendorff大鼠心脏灌流模型,低氧/复氧(H/R)采用冠脉前降支结扎30 min、复灌120 min的方法。用生物信号采集系统记录左室发展压(LVDP)、左室压最大上升/下降速率(±dP/dtmax)、左室舒张末压(LVEDP);分光光度法分别检测冠脉流出液中乳酸脱氢酶(LDH)的含量和线粒体活性氧(ROS);TTC染色法检测心肌梗死面积。结果:与单纯低氧/复氧组相比,复氧起始给予线粒体钙单向转运体抑制剂钌红(5μmol/L)明显改善左心室各项功能指标,减小心肌梗死面积,降低线粒体ROS和冠脉流出液中LDH含量;而在复氧期起始给予线粒体钙单向转运体激动剂精胺(20μmol/L),显著升高了线粒体ROS活性,冠脉流出液中LDH含量在复氧5 min、20 min、30 min时显著增多,左心室各项功能指标与心肌梗死面积与单纯低氧/复氧组相比无显著差异。ROS清除剂MPG(1 mmol/L)与精胺联合应用则取消了精胺的作用。结论:抑制线粒体钙单向转运体可能通过减少线粒体ROS的生成减轻心脏低氧/复氧损伤。     

乙酰胆碱对离体大鼠缺血/复灌心脏的保护作用及其机制

目的:探讨乙酰胆碱(ACh)预处理抗心肌缺血复灌(I/R)损伤作用及其与线粒体渗透性转换孔和/或线粒体ATP敏感性钾通道的关系。方法:采用离体大鼠心脏Langendorff灌流方法进行全心停灌30min,复灌120min复制I/R模型。测定心室力学指标和复灌各时间点冠脉流出液中乳酸脱氢酶(LDH)含量。实验结束测定心肌组织formazan含量的变化。结果:与单纯I/R组相比,ACh(0.1μmol/L,5min)预处理明显提高心肌细胞的formazan含量,降低复灌期间冠脉流出液中LDH含量,明显改善I/R所致的左室发展压、左心室内压最大上升和下降速率、心率与发展压乘积和左室舒张末压力的下降,缓解冠脉流量的减少。线粒体渗透性转换孔开放剂苍术苷(20μmol/L,复灌前给药20min)和线粒体ATP敏感性钾通道抑制剂5-羟基癸酸(100μmol/L,缺血前给药20min)能明显减弱ACh的保护作用。结论:在大鼠离体心脏灌流模型上,ACh预处理具有抗心脏缺血/复灌损伤的作用,这种保护作用可能与其抑制线粒体渗透性转换孔的开放和促进线粒体ATP敏感性钾通道的开放有关。     

葛根素对离体大鼠缺血/复灌心脏的保护作用及其作用机制

目的：探讨葛根素（puerarin,Pue）预处理抗心肌缺血／复灌（ischemia／reperfusion,I／R）损伤是否与线粒体渗透性转换孔和／或线粒体ATP敏感性钾通道有关。方法：采用离体大鼠心脏Leangendorff灌流方法,全心停灌30min,复灌120min复制I／R模型。测定心室力学指标和复灌各时间点冠脉流出液中乳酸脱氢酶（LDH）含量。实验结束测定心肌组织formazan量的变化。结果：与单纯I／R组相比,Pue（0．24mmol／L,5min）预处理明显提高心肌细胞的formazan含量,降低复灌期间冠脉流出液中LDH含量,明显促进左室发展压、左心室内压最大上升和下降速率、心率与发展压乘积和左室舒张末压力的恢复,缓解冠脉流量的减少。线粒体渗透性转换孔开放剂苍术苷（20μmol／L。复灌前给药20min）和线粒体ATP敏感性钾通道抑制剂5-羟基癸酸（100μmol／L,缺血前给药20min）能明显减弱Pue的保护作用。结论：在大鼠离体心脏灌流模型上,Pue预处理具有抗心脏缺血／复灌损伤的作用,这种保护作用可能与其抑制线粒体渗透性转换孔的开放和促进线粒体ATP敏感性钾通道的开放有关。     

心房肽Ⅲ对大鼠离体灌流心脏的影响

为探讨心房肽(atriopeptin,AP)降低心输出量(CO)的机理,我们应用离体作功心脏灌流模型,在去除了神经、体液因素影响的情况下,观察了 APⅢ 对大鼠离体心脏的作用。实验结果表明,APⅢ10mol/L 可使冠脉流量(CF)和 CO 轻度降低,40nmol/L 时对离体心脏具有明显抑制作用,在30s 内使心指数(CI)、每搏指数(SVI)、CF、左室压(LVP)及其微分(LVdp/dt)等多项指标降低。提示 APⅢ 对心脏具有直接抑制作用。APⅢ 使冠脉流量降低,可能是这种抑制作用的重要原因。     

磷酸二酯酶9型抑制剂PF-04449613对大鼠心脏正性肌力作用及其机理

本文旨在研究磷酸二酯酶9型抑制剂PF-04449613对大鼠心脏正性肌力作用及其机理。采用在体双压力-容积环及离体心脏收缩力技术分析其对成年健康大鼠心脏正性肌力的作用特点;运用大鼠心肌细胞钙释放技术分析其作用机理。双压力-容积环实验表明:PF-04449613 (5.5 mg/kg)显著增加大鼠搏出功、心输出量、每博输出量、收缩末期压力及射血分数(P 0.05),降低收缩末期容积、舒张末期容积及舒张末期压力(P 0.05)。PF-04449613对外周动脉血压的作用表现为增加收缩压、降低舒张压及血管阻力(P 0.05)。大鼠离体心脏灌流实验表明,PF-04449613浓度依赖性地增加离体大鼠左心室发展压(P 0.05)。以Fluo-4 AM为钙离子荧光指示剂的钙释放结果表明,PF-04449613 (5μmol/L)显著增强肌浆网钙泵(sarcoplasmic reticulum Ca~(2+)-ATPase-2a,SERCA2a)介导的钙释放下降相的快成分,显著增加大鼠心肌细胞钙释放幅值(P0.05)。PF-04449613 (5μmol/L)降低肌浆网钙泄漏率(P 0.05)。以上结果提示,PF-04449613通过增加SERCA2a活性发挥其对大鼠心脏正性肌力作用。     

低浓度乙醇对糖尿病大鼠心肌损伤后线粒体融合素2表达的影响

目的：探讨低浓度乙醇对糖尿病大鼠心肌损伤后线粒体融合素2（mfn2）表达的影响。方法：糖尿病大鼠模型采用链脲佐菌素55 mg/kg腹腔注射,分为正常对照组（Control组）,糖尿病组（DM组）和糖尿病+乙醇组（DM+EtOH组）（n=6）;糖尿病+乙醇组于造模成功1周后给予2.5%乙醇日常饮用,1周后改为5%的乙醇持续至8周,8周后行离体心脏灌流,测定心室血流动力学指标,应用自动生化分析仪测定血清乳酸脱氢酶（LDH）和天门冬氨酸转移酶（AST）的水平。Western blot测定左心室组织线粒体融合素2（mfn2）蛋白表达,免疫组化测定心肌组织mfn2蛋白表达。结果：与control组大鼠心肌相比,DM组大鼠心率、左室发展压、左室做功下降,左室舒张末压抬高,血清LDH及AST升高明显,心室mfn2蛋白表达降低;与DM组大鼠心肌相比,DM+EtOH组明显促进心率、左室发展压、左室做功的恢复,降低左室舒张末压,同时降低LDH的水平和AST的释放,mfn2的蛋白表达增高。结论：糖尿病大鼠心肌损伤时,心肌mfn2表达降低;低浓度乙醇增强mfn2在心肌组织中的表达,提示mfn2的增加可能参与低浓度乙醇对糖尿病诱发的心肌损伤的保护作用。     

白细胞介素—2对离体大鼠心脏的作用及其机理

The purpose of the present study was to explore the biological effects and mechanism of interleukin-2 (IL-2) on the isolated rat heart. The results showed that hrIL-2 increased the number of premature ventricular contraction, heart rate, left ventricular developed pressure, left ventricular end-diastolic pressure and coronary flow in the isolated perfused rat heart. Heat inactivated hrIL-2 had no effect on the heart. Pretreatment with ryanodine canceled the positive effects of hrIL-2 on left ventricular developed pressure, left ventricular end-diastolic pressure and coronary flow but had no effects on arrhythmogenesis and tachycardia by hrIL-2. Pretreatment with nifedipine or low extracellular calcium abolished the arrhythmogenic effect of hrIL-2 and attenuated partially the augment of heart rate, left ventricular developed pressure, left ventricular end-diastolic pressure and coronary flow. It suggests that the cardiac activity of hrIL-2 depended on the integrity of its spatial structure and transmembrane influx Ca2+ and intracellularly stored Ca2+ were involved in the cardiac activity of hrIL-2.     

Positive inotropic, positive chronotropic and coronary vasodilatory effects of rat amylin: mechanisms of amylin-induced positive inotropy

Even though there are a few studies dealing with the cardiac effects of amylin, the mechanisms of amylin-induced positive inotropy are not known well. Therefore, we investigated the possible signaling pathways underlying the amylin-induced positive inotropy and compared the cardiac effects of rat amylin (rAmylin) and human amylin (hAmylin).Isolated rat hearts were perfused under constant flow condition and rAmylin or hAmylin was infused to the hearts. Coronary perfusion pressure, heart rate, left ventricular developed pressure and the maximum rate of increase of left ventricular pressure (+dP/dtmax) and the maximum rate of pressure decrease of left ventricle (-dP/dtmin) were measured.rAmylin at concentrations of 1, 10 or 100 nM markedly decreased coronary perfusion pressure, but increased heart rate, left ventricular developed pressure, +dP/dtmax and -dP/dtmin. The infusion of H-89 (50 μM), a protein kinase A (PKA) inhibitor did not change the rAmylin (100 nM)-induced positive inotropic effect. Both diltiazem (1 μM), an L-type Ca2+ channel blocker and ryanodine (10 nM), a sarcoplasmic reticulum (SR) Ca2+ release channel opener completely suppressed the rAmylin-induced positive inotropic effect, but staurosporine (100 nM), a potent protein kinase C (PKC) inhibitor suppressed it partially. hAmylin (1, 10 and 100 nM) had no significant effect on coronary perfusion pressure, heart rate and developed pressure, +dP/dtmax and -dP/dtmin.We concluded that rAmylin might have been produced vasodilatory, positive chronotropic and positive inotropic effects on rat hearts. Ca2+ entry via L-type Ca2+ channels, activation of PKC and Ca2+ release from SR through ryanodine-sensitive Ca2+ channels may be involved in this positive inotropic effect. hAmylin may not produce any significant effect on perfusion pressure, heart rate and contractility in isolated, perfused rat hearts.     

Comparison of the effects of neuropeptide Y (NPY) and 4-norleucine-NPY on isolated perfused rat hearts; effects of NPY on atrial and ventricular strips of rat heart and on rabbit heart mitochondria

Isolated perfused rat hearts were used to compare the effects of the synthetic neuropeptide Y (NPY) and 4-norleucine-NPY on cardiac function. Each peptide exhibited both negative inotropic and chronotropic effects, and also caused coronary vasoconstriction leading to a reduction in coronary flow. A comparison of the IC50 values from dose-response curves using 10(-14) to 10(-7) M peptides (IC50 is the peptide concentration that produced a 50% decrease of the maximal effect) indicated that NPY was more potent as inhibitor of contractility and less potently inhibited coronary flow and heart rate, whereas 4-norleucine-NPY had more inhibitory influence on coronary flow and heart rate and less on cardiac contractility. This difference in potencies suggests that the inhibitory effects of NPY on contractility, coronary flow and heart rate may be independent of each other. Since NPY also decreased the contractile force of isolated left atrial and right ventricular strips of the rat heart, the coronary flow decrease cannot be the cause of the negative inotropy of isolated heart. Pretreatment of atrial and ventricular strips with NPY did not influence the positive inotropic effect produced by the cardiac glycoside ouabain indicating that sarcolemmal Na+, K+-ATPase was not involved in the inhibitory inotropic effect of NPY. Further studies towards elucidating the mechanism of the negative inotropy of cardiac muscles using isolated heart mitochondria revealed that NPY uncoupled oxidative phosphorylation and blocked mitochondrial calcium uptake; the former event fosters negative inotropy. Since these effects on mitochondria occurred at concentrations 100-fold higher than those required for negative inotropy, the two effects of NPY may not be related.     

Protease-activated receptor-2 activation improves efficiency of experimental ischemic preconditioning

Protease-activated receptor-2 (PAR-2) is a member of seven transmembrane domain G protein-coupled receptors activated by proteolytic cleavage. PAR-2 is involved in inflammatory events and cardiac ischemic reperfusion injury. The objective of this study was to investigate the effects of PAR-2 in experimental myocardial ischemic preconditioning. To monitor the effects of PAR-2, Langendorff-perfused rat hearts were used. These hearts were treated with PAR-2-activating peptide (PAR-2AP) in various protocols. Hemodynamic parameters (left ventricular developed pressure, left ventricular diastolic pressure, coronary flow rate, and heart rate), several indexes of oxidative injury, and neutrophil accumulation were evaluated. We show for the first time that enhanced PAR-2 activation improves efficiency of ischemic preconditioning and reduces cardiac inflammation in the rat heart. Indeed, after PAR-2AP infusion we found that hemodynamic parameters, oxidative injury, infarct size, and neutrophil accumulation were involved. These data support the concept that PAR-2-dependent cell trafficking may regulate signaling responses to cardiac ischemia and inflammation.     

Acidaemia reduces cardiac output and left ventricular contractility in conscious lambs

We studied the effects of HCI-induced metabolic acidaemia on cardiac output, contractile function, myocardial blood flow, and myocardial oxygen consumption in nine unanaesthetized newborn lambs. Through a left thoracotomy, catheters were placed in the aorta, left atrium and coronary sinus. A pressure transducer was placed in the left ventricle. Three to four days after surgery, we measured cardiac output, dP/dt, left ventricular end diastolic and aortic mean blood pressures, heart rate, aortic and coronary sinus blood oxygen contents, and left ventricular myocardial blood flow during a control period, during metabolic acidaemia, and after the aortic pH was restored to normal. We calculated systemic vascular resistance, myocardial oxygen consumption and left ventricular work. Acidaemia was associated with reduction in cardiac output, maximal dP/dt, and aortic mean blood pressure. Left ventricular end diastolic pressure and systemic vascular resistance increased, and heart rate did not change significantly. The reduction in myocardial blood flow and oxygen consumption was accompanied by fall in cardiac work. Cardiac output returned to control levels after the pH had been normalized but maximal dP/dt was incompletely restored. Myocardial blood flow and oxygen consumption increased beyond control levels. This study demonstrates that HCI-induced metabolic acidaemia in conscious newborn lambs is associated with a reduction in cardiac output which could have been mediated by the reduction in contractile function and/or the increase in systemic vascular resistance. The decreases in myocardial blood flow and oxygen consumption appear to reflect diminished cardiac work. The restoration of a normal cardiac output after normalization of the pH appears to have resulted from the increases in heart rate and left ventricular filling pressures in conjunction with an incomplete restoration of contractile function.     

Hydrogen peroxide enhanced inron-induced injury in isolated heart and ventricular cardiomyocyte in rats

To explore the cardiac effects of iron with or without hydrogen peroxide, the isolated perfused rat heart and enzymatically isolated ventricular cardiomyocyte were used. It was shown that treatment with cell-permeable iron (Fe-HQ) for 10 min reduced the contractile amplitude and velocity and end diastolic cell length in the cardiomyocyte and increased the contents of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary effluent and malondialdehyde (MDA) in the myocardium. The left ventricular developed pressure (LVDP), ± dP/dtmax, and heart rate and coronary flow are showed a biphasic phase, an increase at first followed by a decline. Treatment with hydrogen peroxide for 10 min following Fe-HQ augmented the effect of iron with an increase in coronary LDH and CK release and myocardial MDA content, and decrease in LVDP, ± dP/dtmax and heart rate. Perfusion of reduced glutathione with hydrogen peroxide counteracted these effects of Fe-HQ and hydrogen peroxide while dimethyl sulfoxide had no effect on the injury induced by Fe-HQ and hydrogen peroxide in the isolated rat heart. This suggests that augmentation of myocardial injury as a result of an increase in intracellular iron by hydrogen peroxide might involve the dysfunction of sulfydryl group containing proteins but not the hydroxyl radicals.     

Implication of Substance P in myocardial contractile function during ischemia in rats

Evidence suggests that substance P (SP) participates in the pathology of acute myocardial ischemia and infarction but the profiles of the peptide in regulation of cardiac functions are still elusive. The aim of this study was to investigate the role of substance P in regulation of cardiac functions and its association with adrenergic mechanism in acute myocardial ischemia and infarction with rodent models. The experiments were carried out in Sprague-Dawley rats. SP and norepinephrine were significantly up-regulated in myocardium at 15min, 30min and 60min of coronary artery occlusion. Pretreatment of the rats with a specific antagonist of neurokinin-1 receptor, D-SP, significant increased+dp/dt and decreased -dp/dt, compared with the controls, pretreated with 0.9% saline. Pretreatment of the isolated CAO hearts with substance P (10(-7)mol/L) significantly increased left ventricular end diastolic pressure. SP producing no effects on cardiac functions when given alone to isolated (non-CAO) heart caused significant attenuation of the changes in the contractility and diastolic functions induced by norepinephrine, when given with norepinephrine. SP attenuated the increase in the activity of PKA provoked by norepinephrine in cultured myocytes. In conclusion, the findings may indicate SP regulates cardiac functions via modulation of adrenergic activity, through suppression of over-activation of PKA.     

Proteolytic N-terminal truncation of cardiac troponin I enhances ventricular diastolic function

Besides the core structure conserved in all troponin I isoforms, cardiac troponin I (cTnI) has an N-terminal extension that contains phosphorylation sites for protein kinase A under beta-adrenergic regulation. A restricted cleavage of this N-terminal regulatory domain occurs in normal cardiac muscle and is up-regulated during hemodynamic adaptation (Z.-B. Yu, L.-F. Zhang, and J.-P. Jin (2001) J. Biol. Chem. 276, 15753-15760). In the present study, we developed transgenic mice overexpressing the N-terminal truncated cTnI (cTnI-ND) in the heart to examine its biochemical and physiological significance. Ca(2+)-activated actomyosin ATPase activity showed that cTnI-ND myofibrils had lower affinity for Ca(2+) than controls, similar to the effect of isoproterenol treatment. In vivo and isolated working heart experiments revealed that cTnI-ND hearts had a significantly faster rate of relaxation and lower left ventricular end diastolic pressure compared with controls. The higher baseline relaxation rate of cTnI-ND hearts was at a level similar to that of wild type mouse hearts under beta-adrenergic stimulation. The decrease in cardiac output due to lowered preload was significantly smaller for cTnI-ND hearts compared with controls. These findings indicate that removal of the N-terminal extension of cTnI via restricted proteolysis enhances cardiac function by increasing the rate of myocardial relaxation and lowering left ventricular end diastolic pressure to facilitate ventricular filling, thus resulting in better utilization of the Frank-Starling mechanism.     

Inhibition of Ras-GTPase,but not tyrosine kinases or Ca2+/calmodulin-dependent protein kinase II,improves recovery of cardiac function in the globally ischemic heart

The signaling pathways involved in ischemic heart disease are not well characterized. In this study, the roles of Ras-GTPase, tyrosine kinases (TKs) and Ca2+/calmodulin-dependent protein kinase II (CaMKII) in global ischemia and reperfusion (I/R) in a perfused rat heart model were investigated and compared to beneficial effects produced by preconditioning (PC). A 40 min episode of global ischemia followed by a 30 min reperfusion in perfused rat hearts produced significantly impaired cardiac function, measured as left ventricular developed pressure (Pmax) and left ventricular end-diastolic pressure (LVEDP), and impaired coronary hemodynamics, measured as coronary flow (CF) and coronary vascular resistance (CVR). Hearts from male Wistar rats pre-treated with the tyrosine kinase inhibitor, genistein (1 mg/kg/day for 6 days), or the CaMKII inhibitor, KN-93 (578 ng/min for 6 days), produced detrimental effects on recovery of cardiac function and coronary hemodynamics. In contrast, pre-treatment with Ras-GTPase inhibitor FPT III (232 ng/min for 6 days) significantly enhanced cardiac recovery in terms of left ventricular contractility and coronary vascular hemodynamics. Treatment with FPT III also significantly reduced expression of the sodium-hydrogen exchanger-1 (NHE-1) which was elevated during I/R as detected by Western blotting. These data suggest that TKs and CaMKII are involved in signaling pathways leading to recovery from cardiac ischemia, whereas activation of Ras-GTPase signaling pathways are critical in the development of cardiac dysfunction due to I/R.     

TNF-alpha as a potential mediator of cardiac dysfunction due to intracellular Ca2+-overload

TNF-alpha has been shown to be involved in cardiac dysfunction during ischemia/reperfusion injury; however, no information regarding the status of TNF-alpha production in myocardial injury due to intracellular Ca2+-overload is available in the literature. The intracellular Ca2+-overload was induced in the isolated rat hearts subjected to 5 min Ca2+-depletion and 30 min Ca2+-repletion (Ca2+-paradox). The Ca2+-paradox hearts exhibited a dramatic depression in left ventricular developed pressure, a marked elevation in left ventricular end diastolic pressure, and more than a 4-fold increase in TNF-alpha content. The ratio of cytosolic to homogenate nuclear factor-kappaB (NFkappaB) was decreased whereas the ratio of phospho-NFkappaB to total NFkappaB was increased in the Ca2+-paradox hearts. All these changes due to Ca2+-paradox were significantly attenuated upon treating the hearts with 100 microM pentoxifylline. These results suggest that activation of NFkappaB and increased production of TNF-alpha may play an important role in cardiac injury due to intracellular Ca2+-overload.