辣椒辣素对大鼠再灌注损伤的心肌早期和延迟保护作用

AIM: To study early or delayed cardioprotection afforded by pretreatment with capsaicin. METHODS: The isolated rat heart was perfused in a Langendorff model. Heart rate, coronary flow, left ventricular pressure, and its first derivative (+/- dp/dtmax) were recorded, and the calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) and the release of creatine kinase (CK) were measured. RESULTS: Capsaicin (50 mg.kg-1, s.c.) improved the recovery of cardiac function and decreased the release of CK. CK was (2.12 +/- 0.40) and (0.26 +/- 0.04) u.min-1.g-1(wet wt) for ischemia-reperfusion (I/R) and capsaicin + I/R, respectively (P < 0.05). Capsaicin treatment caused an increase in the concentration of CGRP-LI in plasma. CGRP-LI was (135 +/- 12) and (304 +/- 45) ng.L-1 for vehicle + I/R and capsaicin + I/R, respectively (P < 0.05). After pretreatment with capsaicin to deplete the sensory nerve transmitter content, the cardioprotection and the increased level of CGRP by capsaicin were abolished. A delayed protection was shown in the hearts obtained from the rats pretreated with capsaicin 24 h or 48 h before the experiments. CONCLUSION: Pretreatment with capsaicin induces the early and delayed cardioprotection, which may be related to stimulation of CGRP release in the rat.     

辣椒辣素对大鼠再灌注损伤的心肌早期和延迟保护作用(英文)

目的:研究辣椒辣素预处理的早期和延迟心肌保护。方法:采用Langendorff装置灌注离体心脏,记录心率、冠脉流量、左室内压以及最大变化速率,并测定降钙素基因相关肽(CGRP)的血浆浓度及灌注液中肌酸激酶(CK)的释放量。结果:辣椒辣素(50mg·kg~(-1),sc)改善心功能、降低CK释放,并升高CGRP的血浆浓度。预先用辣椒辣素耗竭感觉神经递质后,辣椒辣素的心肌保护和升高CGRP血浆浓度作用消失,应用辣椒辣素24h或48h后,其对缺血心肌仍具有保护作用。结论:辣椒辣素能诱导早期和延迟心肌保护,其保护作用可能与促进CGRP释放有关。     

Heat stress-induced protection of endothelial function against ischaemic injury is abolished by ATP-sensitive potassium channel blockade in the isolated rat heart

The protection conferred by heat stress (HS) against myocardial ischaemia-reperfusion injury, in terms of mechanical function preservation and infarct size reduction, is well documented and mechanisms underlying these effects have been extensively explored. However, the effect of HS on coronary circulation is less known. The aim of this study was thus to investigate the role of ATP-sensitive potassium (K(ATP)) channels in the protection against ischaemic injury afforded by HS to the coronary endothelial function. Twenty-four hours after whole body hyperthermia (42 degrees C for 15 min, H groups) or sham anaesthesia (Sham groups), isolated perfused rat hearts were subjected to a 15 min stabilization period followed by a 30 min infusion of either 0.3 microM glibenclamide (Gli, a K(ATP) channel blocker) or its vehicle (V). Hearts were then exposed to a low-flow ischaemia (30 min)-reperfusion (20 min) (I/R) or normally perfused (50 min), after which coronaries were precontracted with 0.1 microM U-46619. Finally, the response to the endothelium-dependent vasodilator, 5-hydroxytryptamine (5-HT, 10 microM) was compared to that of the endothelium-independent vasodilator, sodium nitroprusside (SNP, 3 microM). In hearts from Sham-V and Sham-Gli groups, I/R selectively diminished 5-HT-induced vasodilatation without affecting the vasodilatation to SNP. In V-treated groups, prior HS preserved the vasodilatation produced by 5-HT. This HS-induced protection was abolished by Gli treatment. In conclusion, these results suggest that K(ATP) channel activation contributes to the preservation of coronary endothelial function conferred by heat stress against ischaemic insult.     

Mechanisms of the protective effects of urocortin on coronary endothelial function during ischemia-reperfusion in rat isolated hearts

1 Urocortin is a vasodilator peptide related to corticotrophin-releasing factor, which may protect endothelial function during coronary ischemia-reperfusion (I-R). The aim of this study was to study the mechanisms of this protective effect. 2 Hearts from Sprague-Dawley rats were isolated and perfused at constant flow and then exposed to 15 min global zero-flow ischemia, followed by 15 min reperfusion. The relaxation to acetylcholine (10 nM-10 microM) was recorded after pre-constriction of the coronary vasculature with U46619 (100-300 nM) in ischemic-reperfused or time-control hearts. 3 After I-R, the coronary relaxation to acetylcholine was reduced and this reduction was attenuated by treatment with urocortin (10 pM), administered before ischemia and during reperfusion. 4 This urocortin-induced improvement of the relaxation to acetylcholine was not modified by tetraethylammonium (10 mM), blocker of Ca2+ dependent-potassium channels; glibenclamide (10 microM), blocker of K(ATP) channels; N(w)-nitro-L-arginine methyl ester (L-NAME, 100 microM), blocker of nitric oxide synthesis; or meclofenamate (10 microM), blocker of cyclooxygenase, but it was abolished by chelerythrine (3 microM), blocker of protein kinase C (PKC). 5 These results suggest that urocortin may protect coronary endothelial function during I-R by activation of PKC.     

Cardioprotection by polysaccharide sulfate against ischemia/reperfusion injury in isolated rat hearts

Aim:

Polysaccharide sulfate (PSS) is a new type of heparinoid synthesized with alginic acid as the basic material and then by chemical introduction of effective groups. Although PSS is successfully applied in ischemic cardio-cerebrovascular disease, its effect on cardiac function after ischemia/reperfusion (I/R) injury has previously not been investigated. The aim of the present study was to investigate whether PSS can protect the heart from I/R injury and the underlying mechanism of protection.

Methods:

Isolated rat hearts were perfused (Langendorff) and subjected to 20 min global ischemia followed by 60 min reperfusion with Kreb''s Henseleit solution or PSS (0.3–100 mg/L). Myocardial contractile function was continuously recorded. Creatine kinase (CK) and lactate dehydrogenase (LDH) leakage were measured. Tumor necrosis factor-α (TNF-α) expression in cardiomyocytes was investigated. Western blot analysis for extracellular regulated kinases (ERKs), c-jun amino-terminal kinase (JNKs) and p38 mitogen-activated protein kinase (MAPK) activity was performed.

Results:

After I/R, cardiac contractility decreased, CK and LDH levels increased in the coronary effluent, and TNF-α expression increased in cardiomyocytes. PSS administration at concentrations of 1–30 mg/L improved cardiac contractility, reduced CK and LDH release and inhibited TNF-α production. Phosphorylated-p38MAPK (p-p38MAPK) and p-p54/p46-JNK increased in I/R rat hearts but diminished in PSS (1–30 mg/L) treated hearts. P-p44/p42-ERK levels were unchanged. In contrast, high concentrations of PSS (100 mg/L) had adverse effects that caused a worsening of heart function.

Conclusion:

PSS has dose-dependent cardioprotective effects on the rat heart after I/R injury. The beneficial effects may be mediated through normalization of the activity of p38 MAPK and JNK pathways as well as controlling the level of TNF-α expression.     

Cardioprotection by polysaccharide sulfate against ischemia/ reperfusion injury in isolated rat hearts

Aim： Polysaccharide sulfate （PSS） is a new type of heparinoid synthesized with alginic acid as the basic material and then by chemical introduction of effective groups. Although PSS is successfully applied in ischemic cardio-cerebrovascular disease, its effect on cardiac function after ischemia/reperfusion （I/R） injury has previously not been investigated. The aim of the present study was to investigate whether PSS can protect the heart from I/R injury and the underlying mechanism of protection. Methods： Isolated rat hearts were perfused （Langendorff） and subjected to 20 min global ischemia followed by 60 min reperfusion with Kreb＇s Henseleit solution or PSS （0.3-100 mg/L）. Myocardial contractile function was continuously recorded. Creatine kinase （CK） and lactate dehydrogenase （LDH） leakage were measured. Tumor necrosis factor-α （TNF-α） expression in cardiomyocytes was investigated. Western blot analysis for extracellular regulated kinases （ERKs）, c-jun aminoterminal kinase （JNKs） and p38 mitogen-activated protein kinase （MAPK） activity was performed.
Results： After I/R, cardiac contractility decreased, CK and LDH levels increased in the coronary effluent, and TNF-α expression increased in cardiomyocytes. PSS administration at concentrations of 1-30 mg/L improved cardiac contractility, reduced CK and LDH release and inhibited TNF-α production. Phosphorylated-p38MAPK （p-p38MAPK） and p-p54/p46- JNK increased in I/R rat hearts but diminished in PSS （1-30 mg/L） treated hearts. P-p44/p42-ERK levels were unchanged. In contrast, high concentrations of PSS （100 mg/L） had adverse effects that caused a worsening of heart function. Conclusion： PSS has dose-dependent cardioprotective effects on the rat heart after I/R injury. The beneficial effects may be mediated through normalization of the activity of p38 MAPK and JNK pathways as well as controlling the level of TNF-α expression.     

羟苯氨酮对离体鼠心停灌-复灌损伤的保护作用

目的研究羟苯氨酮对全心停灌-复灌损伤的影响。方法采用离体大鼠心脏停灌40 min-复灌30 min模型，从心脏功能、心肌能量代谢、抗氧化、线粒体钙超载及超微结构等方面观察药物作用。结果停灌前和复灌时给予羟苯氨酮(1~10 μmol·L^-1)明显增加复灌时心肌收缩力与冠脉流量，降低冠脉流出液的肌酸磷酸激酶(CPK)活性，对抗损伤所致的心肌三磷酸腺苷(ATP)与磷酸肌酸(PCr)含量降低，增强心肌抗氧化能力，对抗线粒体钙超载，使线粒体超微结构保持得比较完整。结论羟苯氨酮明显对抗停灌-复灌致心肌损伤，为该药保护再灌注损伤提出有力依据。     

雷诺嗪后处理对大鼠离体心肌缺血/再灌注损伤的保护作用

雷诺嗪被认为是新型调节心肌代谢药物,在不影响细胞功能的前提下,降低细胞对氧的需求,改善氧的代谢,缓解心肌缺氧,从而缓解心绞痛[1].雷诺嗪预处理的心肌保护作用已有研究[2],雷诺嗪后处理是否亦具有心肌保护作用尚未见报道.本研究将利用大鼠离体心脏缺血/再灌注损伤模型,观察雷诺嗪后处理的心肌保护效应,并与雷诺嗪预处理比较.     

Exogenous hydrogen sulfide postconditioning protects isolated rat hearts against ischemia-reperfusion injury

Hydrogen sul fi de (H2S) is an endogenous gaseous mediator, produced by cystanthionine-gamma-lysase (CSE) in the cardiovascular system. Hydrogen sulfide given before ischemia can decrease myocardial ischemia and reperfusion injury. The present study investigated: (1) if hydrogen sulfide given at early reperfusion could decrease myocardial ischemia and reperfusion injury; (2) if the protective effects of hydrogen sulfide were related to mitochondrial ATP-sensitive K+ (KATP) channels opening. In isolated rat heart model, treatment of heart with NaHS (H2S donor) at the onset of reperfusion resulted in a concentration-dependent limitation of infarct size and creatine kinase release. The optimal NaHS concentration for cardioprotection is 1 microM. The cardioprotective effects of NaHS (1, 10 microM) were comparable to those of ischemic postconditioning. The KATP channels blocker, Glibenclamide or 5-hydroxydecanoate, reversed the cardioprotective effects of NaHS. The datum provided further evidence that exogenous H2S postconditioning protected rat heart against ischemia and reperfusion injury. Mitochondrial KATP channel opening is implicated in the postconditioning of H2S.     

Mechanisms of hypoxic coronary vasodilatation in isolated perfused rat hearts.

We pharmacologically investigated the potential involvement of nitric oxide (NO), prostacyclin, adenosine, adenosine triphosphate (ATP)-sensitive K (K(ATP)) channel opening and Ca2+-activated K (K(Ca)) channel opening in coronary vasodilatation during 15 min of hypoxia in isolated rat hearts perfused at a constant pressure of 70 mm Hg. The coronary flow suppressed by 10(-4) M Nomega-nitro-L-arginine methyl ester (L-NAME), which corresponds to the NO-dependent flow, decreased to almost zero during hypoxia. In contrast, the NO-dependent coronary flow amounted to approximately 40% of the total coronary flow during normoxia. The suppression of coronary flow by 10(-5) M 8-phenyltheophylline (8-PT), which corresponds to the adenosine-dependent flow, was remarkable in the middle and the late phases of a 15-min hypoxia. The coronary flow suppressed by 2 x 10(-6) M glibenclamide, which corresponds to the K(ATP) channel opening-dependent flow, depended on the agents added to the perfusate. However, there was a marked increase in coronary flow in the early phase of hypoxia in the heart perfused with the combination of 8-PT, 10(-2) M tetraethylammonium (TEA) and L-NAME. During hypoxia, the coronary flow suppressed by TEA, which corresponds mainly to the K(Ca) channel opening-dependent flow, also depended on the agents added to the perfusate. However, during reoxygenation, there was a transient significant increase in any combination of the agents. Our study suggests that hypoxia almost completely inhibits NO production, and that K(ATP) channel opening immediately after hypoxia and subsequent enhanced adenosine production cause a marked hypoxic coronary vasodilatation. It also suggests that K(Ca) channel opening causes vasodilatation during reoxygenation.     

降钙素基因相关肽介导缺血预适应对溶血性磷脂酰胆碱损伤心肌的保护作用

研究心脏缺血预适应(PC)对溶血性磷脂酰胆碱(LPC)损伤心肌作用的影响，并探讨降钙素基因相关肽(CGRP)在PC中的作用. 离体大鼠心脏Langendorff法灌流，记录心率，冠脉流量，左室压和左室压最大上升速率(+dp/dt_max)，并测定灌流液中肌酸磷酸激酶(CPK)含量. 结果显示，LPC能降低各项心功能指标，并使CPK释放增加；PC(缺血5 min， 再灌5min，重复3次)能减轻LPC的损伤作用；PC的心肌保护作用可被选择性CGRP受体拮抗剂CGRP_8-37所取消；预先给予CGRP或辣椒素能产生与PC相同的心肌保护作用. 对照组, LPC, PC+LPC, CGRP_8-37, CGRP_8-37+PC+LPC, CGRP+LPC, CGRP_8-37+CGRP+LPC, 辣椒素+LPC组CPK释放量分别为0.26±0.05, 2.30±0.22, 0.25±0.03, 0.30±0.08, 2.60±0.15, 0.24±0.05, 2.70±0.20和0.25±0.07 μmol·min^-1·g^-1湿组织. 这些结果提示：1) PC对LPC所致心肌损伤具有保护作用；2) PC的保护作用是由CGRP所介导；3) CGRP或辣椒素可模拟PC的保护作用.     

8,14-二氢萨鲁塔里啶碱对缺血心脏舒张功能的保护作用

采用离体大鼠工作心脏缺血模型，观察８，１４－二氢萨鲁塔里啶碱（ＤＨＳ）对心脏舒张功能和对冠脉流出液中肌酸磷酸激酶释放的影响，结果表明，ＤＨＳ可使缺血后－ｄＰ／ｄｔｍａｘ降低，ＬＶＥＤＰ和Ｔ值的增加均显著低于对照组；并使缺血后ＬＶＳＰ、＋ｄＰ／ｄｔｍａｘ的下降百分率减低。说明ＤＨＳ对缺血大鼠心脏的舒张功能有明显保护作用，可改善收缩功能。ＤＨＳ可显著降低缺血后ＣＰＫ的释放，提示其对膜代谢损伤有一定保护作用。     

Ruthenium red improves postischemic contractile function in isolated rat hearts.

The effect of ruthenium red (inhibitor of mitochondrial calcium entry) on reperfusion contractile function and enzyme release was determined in isolated perfused rat hearts and compared with that of diltiazem. The hearts were made ischemic for 25 min and reperfused for 30 min. They were pretreated with 1-10 microM ruthenium red, 1 microM diltiazem, or vehicle. All concentrations of ruthenium red significantly improved reperfusion contractile function without affecting lactate dehydrogenase (LDH) release or contracture. Diltiazem significantly improved reperfusion function and reduced LDH release and contracture formation. Ruthenium red still improved function even when given only during reperfusion. Diltiazem increased reperfusion oxygen consumption and efficiency of oxygen utilization whereas ruthenium red improved efficiency without an increase in oxygen consumption. Diltiazem significantly increased reperfusion functional reserve in these hearts, although ruthenium red did not. Ruthenium red reduced coronary flow and contractile function in nonischemic myocardial tissue and the reduced function appeared to be secondary to the reduced coronary flow as well as to a direct negative inotropic effect. Thus, ruthenium red improved reperfusion contractile function and oxygen efficiency; this may be related to its ability to block mitochondrial calcium uptake.     

Neuroprotection afforded by diazepam against oxygen/glucose deprivation-induced injury in rat cortical brain slices

The aim of the present investigation was to assess neuroprotection exerted by diazepam (0.1-25 microM) in rat cortical brain slices subjected to oxygen-glucose deprivation and reoxygenation. Neuronal injury and neuroprotection were assessed by measuring the release of glutamate and lactate dehydrogenase and tissue water content. Results demonstrate that diazepam exerted neuroprotective effects according to a "U-shaped", hormetic-like, concentration-response curve, with an efficacy window of 0.5-5 microM concentration. Flumazenil (20 microM) fully antagonised neuroprotection afforded by 5 microM diazepam. In conclusion, the hormetic response of diazepam should be taken into consideration when designing experiments aimed at assessing diazepam neuroprotection against ischemia/reoxygenation injury.     

Remote preconditioning-endocrine factors in organ protection against ischemic injury

Cardiovascular disease is the leading cause of death in the United States and developing world. Experimental and clinical studies have demonstrated that a number of interventions including brief periods of ischemia or hypoxia and certain endogenous factors such as opioids, bradykinin, growth factors or pharmacological agents are capable of protecting the heart against post-ischemic contractile dysfunction, arrhythmias and myocardial infarction. This conventional cardioprotection occurs via an autocrine or paracrine action in which these protective factors are released from the heart to act upon itself. Over the last ten years, a growing body of evidence indicates that a brief ischemic insult on one organ releases endogenous factors that protect other organs against a prolonged ischemic insult. This phenomenon, termed remote preconditioning or preconditioning at a distance, implicates an endocrine action, and may involve humoral or neural-endocrine signaling. This review will summarize the endocrine factors identified and implicated in this inter-organ cytoprotection.     

Cicletanine improves myocardial function deteriorated by ischemia/reperfusion in isolated working rat hearts.

The effect of cicletanine, a novel furopyridine antihypertensive drug was compared with that of nitrendipine, a dihydropyridine slow calcium channel blocker, on cardiac function and reperfusion-induced ventricular arrhythmias in isolated working rat hearts subjected to 10-min ischemia induced by ligation of the left main coronary artery followed by 10-min reperfusion. Before ischemia, cicletanine and nitrendipine, perfused at concentrations of 3 x 10(-5), 6 x 10(-5), 10(-4), and 2 x 10(-4) or 10(-8) M, respectively, did not influence heart rate (HR), LV developed pressure (LVDP), its first derivative (LVdP/dtmax), and LV end-diastolic pressure (LVEDP), whereas aortic flow (AF) was decreased by 2 x 10(-4) M cicletanine only. Coronary flow (CF) remained unchanged by various cicletanine concentrations but was slightly increased by nitrendipine. In the concentration range of 3 x 10(-5)-10(-4) M, cicletanine improved AF either in ischemia or during reperfusion, whereas 2 x 10(-4) M had no such effect. Nitrendipine slightly attenuated ischemia/reperfusion-induced decrease in AF. Cicletanine and nitrendipine enhanced LVDP during ischemia. Ischemia-induced deterioration of LVdP/dtmax was reduced by cicletanine, during reperfusion, but this parameter was reduced by nitrendipine and the highest cicletanine concentration. Cicletanine decreased LVEDP significantly during ischemia and reperfusion, but nitrendipine had no such effect. All cicletanine concentrations reduced the incidence of irreversible ventricular fibrillation (VF) during reperfusion, an effect roughly concentration dependent in the range of 3 x 10(-5)-10(-4) M, whereas nitrendipine had no influence on arrhythmias.     

Angiotensin I conversion and coronary constriction by angiotensin II in ischemic and hypoxic isolated rat hearts.

Dose-response curves of angiotensin I (AI, 1.0-1000.0 pmol) and angiotensin II (AII, 1.25-1250.00 pmol) were obtained in isolated rat hearts subjected to control conditions, mild hypoxia (PO2 = 145 mm Hg), reoxygenation, ischemic (perfusion pressure = 35 mm Hg) and reperfusion. Both AI and AII caused dose-dependent coronary flow (CF) of 26 +/- 3 and 27 +/- 2%, respectively. The effects of both AI and AII were substantially attenuated during hypoxia, but were fully restored upon reoxygenation. During ischemia, the effect of AII was unaltered while the effect of AI was enhanced compared to the control (P less than 0.05). This enhancement was reversible on reperfusion. Cardiac conversion of AI, calculated from ED50 values for AI and AII, was significantly increased during ischemia (P less than 0.05). Infusion of saralasin (0.5-5.0 micrograms/min) did not increase CF in any of the groups. We conclude that (1) the coronary vasoconstrictive effect of AII is preserved in ischemia but attenuated in hypoxia and (2) cardiac conversion of AI to AII is enhanced in hearts injured by ischemia.     

Kinetic analysis of the protection afforded by reversible inhibitors against irreversible inhibition of acetylcholinesterase by highly toxic organophosphorus compounds

In organophosphate poisoning, the underlying mechanism of the therapeutic efficacy of carbamate prophylaxis, which was successfully tested in animal experiments, still awaits complete understanding. In particular, it is unclear whether survival is improved by increased acetylcholinesterase activity during the acute phase, when both carbamate and organophosphate are present. This question should be solved experimentally by means of a dynamically working in vitro model. Immobilized human erythrocytes were continuously perfused while acetylcholinesterase activity was monitored in real-time by a modified Ellman method. The concentrations of reversible inhibitors and of paraoxon were varied to assess the influence of both components on the enzyme activity under steady-state conditions. Physostigmine, pyridostigmine and huperzine A were tested for their prophylactic potential. Upon pretreatment with these reversible inhibitors the enzyme was inhibited by 20-90%. Additional perfusion with 1 microM paraoxon for 30 min resulted in a residual activity of 1-4%, at low and high pre-inhibition, respectively. The residual activity was significantly higher than in the absence of reversibly blocking agents (0.3%). After discontinuing paraoxon, the activity increased even in the presence of the reversible blockers. Stopping the reversibly blocking agents resulted in 10-35% recovery of the enzyme activity, depending on the degree of pre-inhibition. The experimental results agreed with computer simulations upon feeding with the essential reaction rate constants, showing that physostigmine was somewhat superior to pyridostigmine in enhancing residual activity in the presence of 1 microM paraoxon for 30 min. The model predicts that inhibitors with a faster dissociation rate, e.g. huperzine A, may be superior in case of a 'hit-and-run' poison such as soman.     

Effect of calmodulin and protein kinase C inhibitors on globally ischemic rat hearts.

Several calmodulin inhibitors have been reported to be cardioprotective, but the ability of these compounds to inhibit protein kinase C (PKC) suggests that calmodulin inhibition may not be the sole mechanism responsible. To distinguish between the effects, we determined the cardioprotective activity of several calmodulin inhibitors with differing PKC inhibitory potencies in isolated globally ischemic rat hearts. Twenty-five minutes of global ischemia caused significant myocardial dysfunction, contracture formation, and lactate dehydrogenase (LDH) release on reperfusion in vehicle-treated hearts. The calmodulin inhibitors trifluoperazine, W-7, calmidazolium, W-13, and CGS 9343B improved postischemic contractile function and/or reduced LDH release. They also reduced preischemic cardiac function, although cardioprotection did not appear to be correlated with cardiodepression. Calmodulin inhibitors increased preischemic coronary flow (CF) and decreased heart rate (HR), but controlling these parameters did not affect the cardioprotection. Pretreatment of ischemic hearts with trifluoperazine was associated with preservation of myocardial ATP. Pretreatment of ischemic rat hearts with the PKC inhibitors staurosporine, calphostin C, polymyxin B, and H-7 did not result in cardioprotection. Thus, calmodulin inhibition causes cardioprotection that appears to be independent of PKC inhibition.     

Isoflurane preconditioning protects against ischemia-reperfusion injury partly by attenuating cytochrome c release from subsarcolemmal mitochondria in isolated rat hearts

AIM: To examine if isoflurane preconditioning can attenuate ischemia/reperfusion injury by reducing cytochrome c release from inner mitochondrial membrane. METHODS: Isolated hearts of Sprague-Dawley rats were perfused on Langendorff apparatus. Hearts were randomly assigned to a non-treated group (CON group, n=12) or three isoflurane preconditioning groups (0.5% ISC group, 1.0% ISC group, and 2.0% ISC group; n=12). In the latter three groups, isoflurane was given at concentrations of 0.5%, 1.0%, and 2.0% for 15 min with 15-min washout before 30-min ischemia. Subsarcolemmal mitochondria of the myocardium were isolated after 60-min reperfusion. Hemodynamics of the each heart was recorded, infarct size of the hearts and contents of cytosolic cytochrome or mitochondrial cytochrome c were measured at the end of reperfusion. Morphology of isolated mitochondria in the four groups was evaluated, respectively. RESULTS: Compared with the CON group, cytosolic cytochrome c in 0.5% ISC group, 1.0% ISC group, and 2.0% ISC group were significantly decreased along with a significant increase of mitochondrial cytochrome c. Infarct size of the hearts in the four groups were 56%+/-12%, 41%+/-12%, 32%+/-7% and 33%+/-11%, respectively. The values of the three isoflurane preconditioning groups were significantly lower than that of the CON group (P<0.05). Isoflurane exposure before ischemia can attenuate the change of morphology of mitochondria after reperfusion. The effects of 2.0% isoflurane on reducing cytochrome c release were more remarkable than 0.5% and 1.0% concentrations of isoflurane. CONCLUSION: Myocardioprotective effects of isoflurane preconditioning were associated with attenuation of cytochrome c loss from the inner membrane of subsarcolemmal mitochondria.