Folic Acid does not limit endothelial dysfunction induced by ischemia and reperfusion: a human study

Nitric oxide synthase (NOS) uncoupling is a condition of increased production of superoxide anion associated with a decreased production of nitric oxide (NO) by this enzyme. Folic acid can prevent and/or reverse NOS uncoupling in the setting of diabetes, smoking, hypercholesterolemia, and nitrate tolerance. Whereas animal studies showed a protective effect of folic acid in ischemia and reperfusion (IR) injury, no study tested whether folic acid administration limits IR-induced endothelial dysfunction in humans. In a double-blind, parallel study, 20 healthy young male volunteers were randomized to receive folic acid, 10 mg/d for 7 days, or matching placebo. At the end of the treatment period, endothelium-dependent, flow-mediated dilation (FMD) of the radial artery was measured before and after IR injury (15 minutes of ischemia at the level of the brachial artery followed by 15 minutes of reperfusion). There was no difference at baseline between groups in any variable. In the placebo group, IR significantly blunted FMD (before IR, 6.7+/-1.0%; after IR, 1.5+/-1.3%, P<0.01). A similar effect was observed in the folic acid group (before IR, 6.3+/-1.1%; after IR, 2.1+/-1.0%, P=ns compared with placebo). As opposed to animal studies, high-dose folic acid does not protect the vascular endothelium from IR injury in humans.     

当归芍药散对脑缺血再灌注所致记忆损伤模型小鼠的影响

目的：观察当归芍药散（DSS）对脑缺血再灌注所致记忆损伤模型的影响。方法：建立小鼠脑缺血再灌注损伤模型,采用避暗实验小鼠记忆功能,并观察DSS对其影响,同时测定小鼠脑内Ca-ATP酶活性、NO含量,蛋白质含量及脑指数、胸腺指数、脾脏指数等。结果：DSS可明显延长脑缺血再灌注损伤模型小鼠避暗潜伏期,明显抑制模型小鼠脑内Ca-ATP酶活性、脑指数及蛋白质含量的降低,明显降低脑内升高的NO含量,对脑缺血再灌所致小鼠脾脏萎缩有显著恢复作用。结论：DSS可能通过升高蛋白质含量、抑制脑萎缩、减轻钙离子超载等环节改善脑缺血再灌注损伤所致小鼠记忆障碍。     

Chrysanthemum morifolium attenuated the reduction of contraction of isolated rat heart and cardiomyocytes induced by ischemia/reperfusion

The present study was aimed to investigate the effect of Chrysanthemum morifolium Ramat. (CM) on isolated rat heart and ventricular myocytes during ischemia/anoxia and reperfusion/reoxygenation. The ischemia/reperfusion injury was induced by ligation the left artery descending coronary of isolated rat heart for 30 min followed by 30 min reperfusion with Langendorff equipment. Cell contraction in enzymatically isolated ventricular myocytes was determined by a video tracking system. The results showed CM (0.25 g/L to 1.0 g/L) increased left ventricular developed pressure (LVDP), +/- dp/dt(max), LVDP x HR and coronary flow (CF) and decreased heart rate (HR) in dose dependent manner. CM (0.5 g/L) attenuated the reduction of LVDP, +/- dp/dt(max) and CF caused by ischemia/reperfusion. CM (0.25 g/L to 1.0 g/L) increased peak velocity of cell shortening/relengthening (+/- dL/dt(max)) and contraction amplitude (dL) of isolated ventricular myocytes in a dose-dependent way under control condition, but without significant effect on end-diastolic cell length (L0). Under anoxia 5 min followed by 10 min reoxygenation, CM attenuated the reduction in contractile parameters. The results suggest that CM processes cardioprotective effect during ischemia/anoxia and reperfusion/reoxygenation in the isolated rat heart and the ventricular myocytes.     

Status of cytokines in ischemia reperfusion induced heart injury

Extensive investigations have implicated cytokines such as tumour necrosis factor (TNF)- alpha and interleukin (IL)-1, and IL-6 as contributing to the pathology of ischemia-reperfusion (I/R) injury, since an increase in the production of those cytokines was clinically detected after myocardial infarction and cardiopulmonary bypass surgery. Current evidence indicates that these cytokines are autocrine contributors to myocardial dysfunction and cardiomyocyte necrosis in I/R injury, whereas, earlier evidence also suggest that cytokines have controversial roles in cardiovascular pathophysiology. Accordingly, it becomes vital to better define the mechanisms of action of cytokines as important steps towards the development of effective therapeutic strategies to combat their deleterious effects in ischemia-induced myocardial injury. Since TNF-alpha, TGF-beta1, IL-1, IL-6 and IL-8 have been frequently studied in cardiovascular diseases, especially in I/R heart disease, the purpose of this article is to review the cardiodepressant role of these cytokines and their release in I/R injury.     

Inhibition of HtrA2/Omi ameliorates heart dysfunction following ischemia/reperfusion injury in rat heart in vivo

High temperature requirement A2 (HtrA2)/Omi is a mitochondrial serine protease that is released into the cytosol from mitochondria and in turn promotes caspase activation by proteolyzing inhibitor of apoptosis proteins. Here we asked whether treatment with an HtrA2/Omi inhibitor, 5-[5-(2-nitrophenyl)furfuryliodine]-1,3-diphenyl-2-thiobarbituric acid (UCF-101), restores heart dysfunction following ischemia/reperfusion injury in vivo. Rats underwent a 30-min ischemia by occluding the left anterior descending artery, followed by 24 h reperfusion. UCF-101 (0.75 or 1.5 micromol/kg, i.p.) was administered 10 min before reperfusion. UCF-101 treatment significantly recovered the mean arterial blood pressure and ameliorated contractile dysfunction of the left ventricle 72 h after reperfusion with concomitant reduction of infarct size. Cardio-protection mediated by UCF-101 was correlated with reduced X-linked inhibitor of apoptosis protein (XIAP) degradation and inhibition of Caspase-9, Caspase-3, and Caspase-7 processing. Furthermore, UCF-101 prevented loss of membrane integrity by inhibiting fodrin breakdown in cardiomyocytes. UCF-101-induced cytoprotection was also correlated with reduced Fas ligand expression and inhibition of FLIP degradation following ischemia/reperfusion. These results suggest that UCF-101 rescues cardiomyocytes from ischemia/reperfusion injury by inhibiting XIAP degradation and Fas/Fas-ligand-induced apoptosis, thereby ameliorating ischemia/reperfusion-induced myocardial dysfunction.     

The administration of oxytocin during early reperfusion, dose-dependently protects the isolated male rat heart against ischemia/reperfusion injury

In our previous study, the administration of oxytocin (OT) could precondition the heart against ischemia/reperfusion injury. In this study, to investigate the cardiac postconditioning effect of oxytocin, isolated rat hearts were mounted on a Langendorff perfusion apparatus. In all groups, the hearts underwent 30 min of regional ischemia followed by 120 min of reperfusion. In the ischemia/reperfusion (IR) group, ischemia and reperfusion was induced. In the ischemic postconditioning (Ipost) group, hearts underwent 6 cycles of 10s reperfusion and 10s ischemia at the beginning of reperfusion. In the other groups (III-IX), OT was perfused 5 min before the onset of reperfusion and continued for 25 min with following doses (Molar): 10(-12), 5 × 10(-12), 8 × 10(-12), 10(-11), 2 × 10(-11), 5 × 10(-11), and 10(-10). The infarct size and coronary effluent levels of creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH) and malondialdehyde (MDA) were calculated at the end of reperfusion. The infarct size decreased considerably in Ipost group compared to IR group (P<0.05). Also, the infusion of oxytocin by doses of 8 × 10(-12)M, 10(-11)M and 2 × 10(-11)M dose-dependently reduced infarct size (P<0.05) significantly compared to the IR group. LDH level in coronary effluent was markedly decreased in Ipost group and treatment with oxytocin by doses of 8 × 10(-12)M, 10(-11)M, 2 × 10(-11)M and 5 × 10(-11)M (P<0.05) compared to IR group. Ipost, OT 2 × 10(-11)and 10(-11)M significantly decreased CK-MB level (P<0.05). Ipost, OT 8 × 10(-12), 10(-11) and 2 × 10(-11)M significantly decreased MDA level as compared to IR group. Our study shows that oxytocin dose-dependently exerts cardiac postconditioning.     

Zn~(2+)诱导金属硫蛋白表达对大鼠缺血再灌注心肌的保护作用

目的　探讨Zn2 + 诱导金属硫蛋白表达对离体大鼠缺血再灌注 (I/R)损伤心肌的保护作用及其机制。方法　 32只Sprague Dawley大鼠随机分为 4组 :对照组、I/R组、Zn2 + 预处理组、心肌组织细胞外信号调节的蛋白激酶 (ERK)抑制剂PD980 5 9+Zn2 + 预处理组 (每组各 8只 )。分别检测心肌细胞乳酸脱氢酶 (LDH)及肌酸激酶 (CK)漏出量、心肌组织三磷酸腺苷 (ATP)含量及心功能指标 (LVSP与±dp/dtmax) ,用10 9Cd/血红素饱和法测量心肌组织中金属硫蛋白的含量。结果　与I/R组比较 ,Zn2 + 预处理组金属硫蛋白表达量增高 (P <0 0 1) ,心肌细胞LDH与CK漏出量降低 ,而心肌组织ATP增高 ,心功能指标改善 (P <0 0 1) ;Zn2 + 预处理组与对照组比较 ,两组间的LDH、CK、ATP、LVSP与±dp/dtmax差异无显著性。ERK抑制剂PD980 5 9取消Zn2 + 预处理组的上述心肌保护作用。结论　Zn2 + 诱导金属硫蛋白表达减轻大鼠心肌I/R损伤 ,其机制涉及丝裂原激活的蛋白激酶 (MAPK)途径     

Endothelin-1诱导的大鼠局灶性脑缺血再灌注模型

目的　研究Endothelin 1(ET 1)诱导的大鼠局灶性脑缺血再灌注模型。方法　将ET 1注入大脑中动脉 (MCA)附近 ,ET 1强烈的缩血管作用可使脑血流 (CBF)降低造成缺血性脑损伤 ,采用氢清除法监测缺血过程中大鼠纹状体脑血流的变化 ,于缺血后 6h进行神经功能评分 ,并采用TTC染色法观察脑梗死面积的变化。结果　ET 1可使纹状体血流呈现浓度依赖性的降低 ,10min时CBF降至最低 ,分别为 :ET 130 0 pmol组 (2 7 1± 2 9) %、36 0pmol组 (12 7±2 1) %、4 0 0pmol组 (11 9± 1 8) %、5 0 0 pmol组 (9 5±1 6 ) % ;神经功能评分显示ET 1可造成大鼠不同程度的神经功能损伤 ;MCAO后 2 4h ,脑梗死面积百分率随ET 1浓度的增加而呈上升趋势 ,并显示出良好的浓度依赖关系 :30 0pmol组 (3 9± 0 3) %、36 0 pmol组 (7 4± 0 5 ) %、4 0 0 pmol组 (11 3± 1 3) %、5 0 0 pmol组 (16 2± 1 8) % ;r =0 992 6(P <0 0 5 )。结论　该模型操作简单 ,造成的脑梗死范围稳定、重现性好 ,是一种更接近人类卒中具体情况的较理想的局灶性脑缺血再灌注模型     

The roles of kupffer cells in hepatic dysfunction induced by ischemia/reperfusion in rats

This study examined the role of Kupffer cells in altering the hepatic secretory and microsomal function during ischemia and reperfusion (Is/Rp). Rats were subjected to 60 min of hepatic ischemia, followed by 1 and 5 h of reperfusion. Gadolinium chloride (GdCl3, 7.5 mg/kg body weight, intravenously) was used to inactivate the Kupffer cells 1 day prior to ischemia. Is/Rp markedly increased the serum aminotransferase level and the extent of lipid peroxidation. GdCl3 significantly attenuated these increases. Is/Rp markedly decreased the bile flow and cholate output, and GdCl3 restored their secretion. The cytochrome P450 content was decreased by Is/Rp. However, these decreases were not prevented by GdCl3. The aminopyrine N-demethylase activity was decreased by Is/Rp, while the aniline p-hydroxylase activity was increased. GdCl3 prevented the increase in the aniline p-hydroxylase activity. Overall, Is/Rp diminishes the hepatic secretory and microsomal drug-metabolizing functions, and Kupffer cells are involved in this hepatobiliary dysfunction.     

Oxidative stress induced by thyroid dysfunction in rat erythrocytes and heart

The aim of this study was to determine whether the effects of thyroid dysfunction induce oxidative stress in the blood and heart of male Wistar rats. Rats were randomly divided into three groups: group I served as control rats. Group II was treated daily with 0.05% benzythiouracile (BTU) administered in drinking water. Rats of group III have received l-thyroxine sodium salt (0.0012%), in drinking water. The results showed that thyroid dysfunction rats had poor growth performance. On the other hand, in hyperthyroid rats, a marked decrease compared with control occurred of some hematological parameters such red blood cell number (RBC), haemoglobin (Hb) concentration and haematocrit (Ht). There was also a significant increase in erythrocyte numbers and heart TBARS concentrations in hypothyroid rats compared with control. These results were associated with a fall in the total antioxidant status (TAS) in the serum of the hyperthyroid rats. Alteration of the antioxidant system in the hypo-/hyperthyroidism-induced rats was confirmed by the significant increase of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities and a decline in glutathione (GSH) content in both tissues were detected in hyperthyroid group compared to controls. On the other hand, serum transaminase activities (aspartate transaminase (AST); alanine transaminase (ALT)) were elevated indicating hepatic cellular damage after treatment with exogenous L-thyroxine. Moreover, serum lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT) and creatine phosphokinase (CPK) activities were increased in the hyperthyroidism rats. These results indicated that excessive thyroxin (long term) ingestion had an adverse effect on animal health and performance. We conclude that thyroid dysfunction induces oxidative stress and modifies some biochemical parameters of erythrocytes, heart and liver disease; our results show the occurrence of a state of oxidizing stress in relation to hyperthyroidism.     

Pyrrolidine dithiocarbamate reduces renal dysfunction and injury caused by ischemia/reperfusion of the rat kidney

Dithiocarbamates can modulate the expression of genes associated with inflammation or development of ischemia/reperfusion injury. Here, we investigate the effects of pyrrolidine dithiocarbamate, an inhibitor of nuclear factor (NF)-kappaB activation, on the renal dysfunction and injury caused by ischemia/reperfusion of the rat kidney. Bilateral clamping of renal pedicles (45 min) followed by reperfusion (6 h) caused significant renal dysfunction and marked renal injury. Pyrrolidine dithiocarbamate (100 mg/kg, administered i.v.) significantly reduced biochemical and histological evidence of renal dysfunction and injury caused by ischemia/reperfusion of the rat kidney. Furthermore, pyrrolidine dithiocarbamate markedly reduced the expression of inducible nitric oxide synthase (iNOS) protein and significantly reduced serum levels of nitric oxide. Finally, pyrrolidine dithiocarbamate inhibited the activation of NF-kappaB by preventing its translocation from the cytoplasm into the nuclei of renal cells. These results demonstrate that pyrrolidine dithiocarbamate reduces renal ischemia/reperfusion injury and that dithiocarbamates may provide beneficial actions against ischemic acute renal failure.     

氟卡胺对豚鼠工作心脏缺血复灌诱发心率失常的影响

用离体豚鼠工作心脏模型研究了抗心律失常药物氟卡胺诱发心律失常的初步机理。结果发现，氟卡胺在１，１０μｍｏｌ·Ｌ－１范围内对缺血复灌诱发的心律失常有明显的保护作用。但１００μｍｏｌ·Ｌ－１的氟卡胺对此模型诱发的心律失常不但无对抗作用，反而能加重和诱发心律失常。当氟卡胺１００μｍｏｌ·Ｌ－１同时加入ｌμｍｏｌ·Ｌ－１维拉帕米对此模型诱发的心律失常表现出明显的对抗作用，作用强于维拉帕米和氟卡胺单独使用。提示大剂量氟卡胺由于较强的抑制了心肌细胞钠、钾电流，从而使钙通道活性过高而产生心律失常。     

Oral administration of a soy extract improves endothelial dysfunction in ovariectomized rats

Effects of oral administration for 4 weeks of a soy fraction with mainly isoflavones (Glycine max, Leguminosae) (SOYPH; 5 mg/kg) on vascular dysfunction induced by bilateral ovariectomy (OVX) in rats were studied. We evaluated vascular reactivity of aortic rings after acetylcholine (ACh 10 nM-10 microM), sodium nitroprussiate (SN 15 - 30 nM) and NG-L-arginine (L-NMA; 10 - 100 microM). Uterine weight and nitric oxide synthase (NOS) activity were also investigated. The same parameters were observed after 4 weeks treatment with 17beta-estradiol. In OVX rats endothelial-dependent vascular responses were changed: reduction of induced contraction ( L-NMA 100 mM: sham OVX 2.1 +/- 0.2 g/mg tissue; OVX 1.7 +/- 0.4 g/mg tissue). Ovariectomy produced a reduction of constitutive NOS activity. Uterine weight was increased in animals treated with 17beta-estradiol but not with SOYPH. Either SOYPH or 17beta-estradiol produced a similar improvement of endothelial dysfunction and increased NOS activity. Our data suggest that soy isoflavones produce an improvement of endothelial dysfunction induced by ovariectomy so as 17beta-estradiol, but probably without changes in reproductive system.     

离体大鼠心肌局部缺血/再灌注模型制备方法的改良

目的改进离体大鼠心肌局部缺血/再灌注损伤模型的制备方法。方法在传统造模的基础上进行改良,采用在结扎线下加一硬塑管打双结的方法,阻断冠状动脉左前降支,局部缺血30min,再灌注180min。分别测定改良组和传统组的心肌梗死面积、漏出液肌酸激酶(CK)活力。结果改良组梗死区/缺血危险区为(45±7)%、变异系数(CV)为15%,CK活力为(382±18)U/ml、CV为5%;传统组梗死区/缺血危险区为(43±11)%、CV为25%,CK活力为(364±30)U/ml、CV为8%。结论改进后的模型制作方法其心肌缺血稳定、可靠,技术难度低,提高了造模的成功率,较传统法具有显著的优越性。     

Assessment of ileal epithelial P-glycoprotein dysfunction induced by ischemia/reperfusion using in vivo animal model

We presented the ischemia/reperfusion (I/R) model which can evaluate changes in P-glycoprotein (P-gp) function induced by lipid peroxidation using surgical-sutures connected with the spring balance. The superior mesenteric artery and vein was occluded by hanging itself using surgical-sutures connected with the spring balance for 60 min (ischemia), followed by reperfusion by cutting of sutures. To determine the hanging force of blood vessel during ischemia, treatment at the hanging force of 50g load, 100g load and 150g load for 60 min was carried out and survival rate was evaluated. Although our 150g load group had some effect on survival, the survival was 100% in the case of 50g and 100g load groups. Thiobarbituric acid-reactive substance (TBA-RS) as an indicator of lipid peroxidation and P-gp expression level after I/R was increased and decreased in a load-dependent manner during ischemia, respectively. Also, the decrease in the level of mdr1a mRNA and function of P-gp by I/R depended on load during ischemia. The changes in TBA-RS, P-gp expression level and P-gp function observed in this study corresponded with our in vitro I/R model reported previously. In conclusion, it was shown that this in vivo I/R model can evaluate the function of P-gp through lipid peroxidation.     

Antioxidant and prooxidant properties of ascorbic acid on hepatic dysfunction induced by cold ischemia/reperfusion

Oxidative stress, which has been generated during reperfusion after a liver transplant, has been implicated in the higher rates of postoperative organ dysfunction. The aim of this study was to examine the effect of ascorbic acid on reperfusion injury after hepatic cold preservation. Isolated perfused rat livers were preserved in a University of Wisconsin solution for 30 h at 4 °C. The bile output was significantly lower after cold ischemia/reperfusion. In contrast, the portal pressure, lactate dehydrogenase and purine nucleoside phosphorylase activities were elevated by cold ischemia/reperfusion. These changes were attenuated at ascorbic acid concentrations of 0.25 and 0.5 mM. However, they were augmented at a concentration of 2 mM. Cold ischemia/reperfusion decreased the reduced to oxidized glutathione ratio, whereas it increased the level of lipid peroxidation and mitochondrial swelling. These changes were prevented exposing the liver to 0.5 mM ascorbic acid but were augmented at 2 mM ascorbic acid. These results suggest that cold ischemia/reperfusion injury is associated with a higher level of oxidative stress and ascorbic acid may act not only as an antioxidant but also as a prooxidant during cold ischemia/reperfusion.     

中叶素抑制大鼠心脏缺血/再灌注损伤

目的研究中叶素(Intermedin,IMD)对大鼠心脏缺血/再灌注(ischemia/reperfusion,I/R)损伤的保护作用及其可能机制。方法Langendorff方法灌流离体心脏,并造成I/R模型,以Power Lab多导生理记录仪记录灌流心脏心功能的变化,收集灌流后心肌组织及灌流液进行生化检测。结果IMD再灌注明显改善I/R造成的心功能抑制和组织损伤,可升高△LVP、LV±dp/dtmax,降低LVDP,增加心率及冠脉流量,同时使心肌LDH、总蛋白和肌红蛋白的漏出及心肌组织MDA生成明显减少,而心肌组织cAMP含量明显增加。且IMD的上述效应与同浓度ADM的效果相近。此外,I/R后心肌IMD受体Bmax和Kd值均增加。结论IMD有明显的抑制心脏I/R损伤的作用,该作用可能通过cAMP途径介导,且IMD抗I/R损伤的作用与强内源性心血管保护肽肾上腺髓质素相仿。     

Probucol reduces myocardial dysfunction during reperfusion after short-term ischemia in rabbit heart.

The effects of probucol, a lipophilic antioxidant, on the myocardial dysfunction (stunning) observed during reperfusion after 15-min ischemia in rabbit heart were studied. Rabbits received food with or without 1% probucol for 3 weeks. They were then anesthetized and prepared for recording of myocardial segment shortening, arterial blood pressure (BP), left ventricular pressure (LVP), rate of development of LVP (dP/dt), and a lead II ECG. Regional myocardial ischemia was produced by acute occlusion of the first marginal branch of the left coronary artery. Myocardial segment shortening was depressed after reperfusion in control rabbits. In comparison, myocardial segment shortening was significantly greater in probucol-treated rabbits than in control rabbits during reperfusion, indicating a beneficial effect. No hemodynamic or ECG changes measured could explain this difference. The number of premature ventricular contractions was reduced in the probucol-treated group, although the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF) were not. Concentrations of probucol in serum and heart of five rabbits were 15.0 +/- 1.2 micrograms/ml and 17.5 +/- 2.5 micrograms/g (mean +/- SEM), respectively. Only probucol concentrations in the serum were positively correlated with the improvement in myocardial segment shortening (r = 0.91, p = 0.03). We conclude that a clinically relevant serum concentration of probucol reduces ischemia-induced myocardial stunning in the rabbit.     

脂氧素A_4对大鼠肺缺血再灌注损伤氧化损伤的影响

目的探讨脂氧素A_4对大鼠肺缺血再灌注损伤氧化应激的影响。方法取36只大鼠(体重220~280g)随机分为假手术组、缺血再灌注组和脂氧素A_4干预组。阻断左肺门45min后再灌注2h建立肺缺血再灌注损伤模型,脂氧素A_4干预组在大鼠恢复血供前5min股静脉注射脂氧素A4 0.1mg/kg。收集标本,检测肺组织的湿/干重量(W/D)比值、支气管肺泡灌洗液的蛋白总量(TP)、检测肺组织匀浆中丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性。结果缺血再灌注组肺组织W/D比值、MDA水平和支气管肺泡灌洗液中总蛋白均较假手术组明显升高,而SOD活性较假手术组明显降低(P0.05)。脂氧素A_4干预组的上述指标高于明显低于缺血再灌注组,而SOD活性较缺血再灌注组明显升高(P0.05)。结论脂氧素A_4对大鼠肺缺血再灌注损伤有一定的保护作用,其机制可能是脂氧素A_4清除自由基抗氧化作用。     

Cardioprotective effects of 9-hydroxyellipticine on ischemia and reperfusion in isolated rat heart

We determined the effect of 9-hydroxyellipticine (9HE) on ryanodine receptor (RyR) and cardiac function after global ischemia in isolated rat hearts. The binding of [3H]-ryanodine in rabbit cardiac sarcoplasmic reticulum was displaced by 9HE in a biphasic manner corresponding to the two sites model with IC50 values of 6.1 microM and 55 mM. The increase of the intracellular Ca2+ concentration induced by caffeine in CHO cells expressing cardiac-type RyR was suppressed by 9HE in a concentration-dependent manner. Pretreatment of the heart with 9HE decreased the total duration of reperfusion-induced ventricular fibrillation (VF) and delayed the onset of VF. There was also a significant recovery of contractile force of ischemic hearts following 9HE. Unlike nifedipine, an L-type Ca2+-channel blocker, 9HE did not suppress the contraction of rat papillary muscles. Thus, 9HE exerts the cardioprotective effects against ischemia /reperfusion injury without changing hemodynamic indices.