Network pharmacology and subsequent experimental validation reveal the synergistic myocardial protection mechanism of Salvia miltiorrhiza Bge.and Carthamus tinctorius L.

Objective:To reveal the molecular mechanism underlying the compatibility of Salvia miltiorrhiza Bge(S.miltiorrhiza,Dan Shen)and C.tinctorius L.(C.tinctorius,Hong Hua)as an herb pair through network pharmacology and subsequent experimental validation.Methods:Network pharmacology was applied to construct an active ingredient-efficacy target-disease protein network to reveal the unique regulation pattern of s.miltiorrhiza and C.tinctorius as herb pair.Molecular docking was used to verify the binding of the components of these herbs and their potential targets.An H9c2 glucose hypoxia model was used to evaluate the efficacy of the components and their synergistic effects,which were evaluated using the combination index.Western blot was performed to detect the protein expression of these targets.Results:Network pharmacology analysis revealed 5 pathways and 8 core targets of s.miltiorrhiza and C.tinctorius in myocardial protection.Five of the core targets were enriched in the hypoxia-inducible factor-1(HIF-1)signaling pathway.S.miltiorrhiza-C.tinctorius achieved vascular tone mainly by regulating the target genes of the HIF-1 pathway.As an upstream gene of the HIF-1 pathway,STAT3 can be activated by the active ingredients cryptotanshinone(Ctan),salvianolic acid B(Sal.B),and myricetin(Myric).Cell experiments revealed that Myric,Sal.B,and Ctan also exhibited synergistic myocardial protective activity.Molecular docking verified the strong binding of Myric,Sal.B,and Ctan to STAT3.Western blot further showed that the active ingredients synergistically upregulated the protein expressionof STAT3.Conclusion:The pharmacodynamic transmission analysis revealed that the active ingredients of S.miltiorrhiza and C.tinctorius can synergistically resist ischemia through various targets and pathways.This study provides a methodological reference for interpreting traditional Chinese medicine compatibility.

Effects of Warm Blood Cardioplegic Solution on Myocardial Protection

To evaluate the effects of warm blood cardioplegic solution on myocardial protection, normothermic induction and terminal perfusion of oxygenated blood cardioplegia in combination with intermittent administration of cold blood cardioplegia during ischemia were studied in an isolated working rat heart model.The experimental protocol consisted of a 120 min cardioplegic arrest followed by 45 min normothermic reperfusion. Myocardial content of adenosine triphosphate (ATP), recovery of the left ventricular function, release of creatine phosphokinase (CPK) and ultrastructure of myocardium were assessed before and after ischemia. The results showed that the hearts preserved with warm blood cardioplegic induction and terminal perfusion had significantly higher levels of ATP,better recovery of cardiac function and lower releases of CPK than those receiving cold blood cardioplegia alone, with myocardial tissue being of generally normal structure. These findings suggest that warm induction and terminal perfusion of blood cardioplegic solution can accelerate myocardial metabolic and functional recovery, preserve high-energy phosphate, reduce myocardial injury and enhance myocardial protection.

Experimental and Clinical Research of Myocardial Protection Effect Using MHBC Perfusion

Objectives To determine themyocardium -protecting effect of medium hypothermalblood cardioplegia (MHBC); further demonstrates thatthe optimal temperature between these hypothermaland normothermic can overcome the disadvantages;and thus discovers a more effective myocardium pro-tecting method. Methods Section 1: 14 mongreldogs (15-20 kg) were randomly divided into twogroups: experimental group and control group; car-dialpulmonary bypass was conventionally instituted,moderate hypothermia blood cardioplegia was used inexperimental group, Blood samples from right atriumtaken for examination of lactate dehydrogenase (LDH)creatine kinase(CK-MB) and Topin Ⅰ(cTn-Ⅰ). speci-mens of left ventricular subendocardial myocardiumwere biopsied to observe changes of ultrastructure.Section 2: 24 patients were randomly divided into twogroups and both groups received two types of treat-ment (same as Section 1) after aorta cross-clamp(ACC). Biochemical index and Clinical observationwere caculated as the indicators. Results In the ex-perimental research, LDH, CK-MB, cTn-Ⅰ were foundincreased afer reperfusion in both groups, but the ex-tent of changes in experimental group is tiny (statisti-cal difference). Compared with control group the effectof MHBC on cardial function is litile; the ultrastruc-ture. of cardiac muscle has no obvious change. In theclinical research, compared the test results of venousblood drawn before CPB, after beating recovery andafter CPB, CBC perfused group (LDH, CK-MB leak-age and cTn-Ⅰ value increase.) compared with MHBCperfused group had no remarkable difference (P>0.05), but at the result of clinical observation: MHBCperfused group had red, soft hearts after cardiac arrestbut CBC perfused group had pale, spasmatic heartsafter cardiac arrest; 0 case in MHBC perfused groupand 3 cases in CBC perfused group had twitch-re-moving beat recovery; 11 cases in MHBC perfusedgroup and 3 cases in CBC perfused group recoveredsinus heart rhythm after surgery; average consumptionof lidocaine was 16.67 (±55.28) mg for MHBC per-fused group and 118.33(±82.65) mg for CBC perfusedgroup (P<0.01) afer surgery; 4 cases in MHBC per-fused group and 11 cases in CBC perfused group suf-fered arrhythmia after surgery. Conclusions As anew myocardium - protecting method, MHBC perfusionin combination with natural body temperature drop ofCPB is worth clinical dissemination and application.

Efficacy of electroacupuncture on myocardial protection and postoperative rehabilitation in patients undergoing cardiac surgery with cardiopulmonary bypass:a systematic review and Meta-analysis

OBJECTIVE:To evaluate the efficacy of electroacupuncture(EA)intervention on myocardial protection and postoperative rehabilitation in patients undergoing cardiac surgery with cardiopulmonary bypass(CPB).METHODS:Eight databases,including Pub Med,Embase,the Cochrane Library,Web of Science,Chinese Bio Medical Literature Database,China National Knowledge Infrastructure Database,Wanfang Data,China Science and Technology Journal Database,and two clinical trial registries,were searched.All randomized controlled trials(RCTs)related to EA intervention in cardiac surgery with CPB were collected.Based on the inclusion and exclusion criteria,two researchers independently screened articles and extracted data.After the quality evaluation,RevMan 5.3 software was used for analysis.RESULTS:Fourteen RCTs involving 836 patients were included.Compared with the control treatment,EA significantly increased the incidence of cardiac automatic rebeat after aortic unclamping[relative risk(RR)=1.15,95%confidence interval(CI)(1.01,1.31),P<0.05;moderate].Twenty-four hours after aortic unclamping,EA significantly increased the superoxide dismutase[standardized mean difference(SMD)=0.96,95%CI(0.32,1.61),P<0.05;low],and interleukin(IL)-2[SMD=1.33,95%CI(0.19,2.47),P<0.05;very low]expression levels and decreased the malondialdehyde[SMD=-1.62,95%CI(-2.15,-1.09),P<0.05;moderate],tumour necrosis factor-α[SMD=-1.28,95%CI(-2.37,-0.19),P<0.05;moderate],and cardiac troponin I[SMD=-1.09,95%CI(-1.85,-0.32),P<0.05;low]expression levels as well as the inotrope scores[SMD=-0.77,95%CI(-1.22,-0.31),P<0.05;high].There was no difference in IL-6 and IL-10 expression levels.The amount of intraoperative sedative[SMD=-0.31,95%CI(-0.54,-0.09),P<0.05;moderate]and opioid analgesic[SMD=-0.96,95%CI(-1.53,-0.38),P<0.05;low]medication was significantly lower in the EA group than in the control group.Moreover,the postoperative tracheal intubation time[SMD=-0.92,95%CI(-1.40,-0.45),P<0.05;low]and intensive care unit stay[SMD=-1.71,95%CI(-3.06,-0.36),P<0.05;low]were significantly shorter in the EA group than in the control group.There were no differences in the time to get out of bed for the first time,total days of antibiotic use after surgery,or postoperative hospital stay.No adverse reactions related to EA were reported in any of the included studies.CONCLUSIONS:In cardiac surgery with CPB,EA may be a safe and effective strategy to reduce myocardial ischaemia-reperfusion injury and speed up the recovery of patients after surgery.These findings must be interpreted with caution,as most of the evidence was of low or moderate quality.More RCTs with larger sample sizes and higher quality are needed to provide more convincing evidence.

Myocardial protection during heart surgery in China

Myocardial protection （MP） is the key for cardiopulmonary bypass （CPB） heart surgery. MP during cardiac surgery （CS） aims to preserve myocardial function while providing a bloodless and motionless operating field. Strategies on how to attenuate or prevent post-ischemic myocardial dysfunction that occurs intra-operatively during CS have been discussed for more than half a century. In 1950, Bigelow et al, first reported to decrease myocardial oxygen demand by means of hypothermia. Moreover, Melrose and coworkers2 described the use of electromechanical cardiac arrest induced by potassium infusion, permitting CS to be performed on a non-beating flaccid heart and clear surgical field. The combination of both of these techniques has been the golden standard in MP during surgery until now, allowing surgery with excellent clinical outcome. In 1975, Braimbridge et al introduced a crystalloid solution into clinical practice at St. Thomas Hospital. By the 1980s, blood-based potassium solutions were advocated to further improve MP and to reduce myocardial enzymes release based on the theory that blood would be a superior delivery vehicle for its oxygenating and buffering capacity.Fortunately, the majority of MP strategies now available do allow patients to undergo conventional and complex CS with an operative mortality rate ranging from less than 2% to 4%.

MORPHOMETRIC EVALUATION ON MYOCARDIAL PROTECTION OF COLD CRYSTALLOID VERSUS WARM BLOOD CARDIOPLEGIA

Twenty patients undergoing open-heart valve replacement were divided randomly into two groups in this study; intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulmonary bypass (CPB) (hypothermic group) and continuous administration of warm blood cardioplegia with normothermic CPB (normothermic group) respectively. Tissue samples were taken from the right atrium before weaning from CPB and from the right appendage 30 minutes after removal of the cross-clamp. The results of pathological study in these two groups were as follows: the structural alterations were most severe during the ischemic period in the hypothermic group. Damages of the myocardial

Blocking the Aryl Hydrocarbon Receptor Alleviates Myocardial Ischemia/Reperfusion Injury in Rats

Objective Restoring the blood perfusion of ischemic heart tissues is the main treatment for myocardial ischemia.However,the accompanying myocardial ischemia reperfusion injury(IRI)would aggravate myocardial damage.Previous studies have confirmed that aryl hydrocarbon receptor(AhR)is closely correlated to kidney and intestinal IRI.The present study aimed to explore the relationship between AhR and myocardial IRI.Methods An oxygen glucose deprivation/reoxygenation(OGD/R)model of H9c2 cells and an ischemia/reperfusion(I/R)model of Sprague-Dawley rat myocardium were established.OGD/R cells and myocardial IRI rats were treated with different concentrations of the AhR antagonist CH-223191 or agonist 6-formylindolo[3,2-b]carbazole(FICZ).Under the conditions of normoxia and hypoxia/reoxygenation,the activity of cardiomyocytes,lactate dehydrogenase(LDH)and cell reactive oxygen species(ROS)were detected.In rats,myocardial pathological damage and markers of myocardial injury were detected.Results According to the results of the cell viability,LDH and ROS tests in vitro,both CH-223191 and FICZ showed no myocardial protection under OGD/R conditions.However,the histological staining and analysis of myocardial injury marker LDH in vitro revealed that CH-223191 could significantly reduce the myocardial IRI.Conclusion AhR exhibited a different effect on myocardial IRI in vitro and in vivo.In vivo,CH-223191 could significantly alleviate the myocardial IRI,suggesting that inhibition of AhR may play a role in myocardial protection,and AhR may serve as a potential treatment target for myocardial IRI.

Effect of Amino Acid Cardioplegia on Myocardial Metabolism and Function of Ischemic Canine Heart

To evaluate the effect of amino acid cardioplegia on myocardial metabolism and function of ischemic canine heart, canine cardiopulmonary bypass (CPB) model was established and the dog heart was subjected to a 120 min ischemic arrest. Animals were divided into 3 groups, group 1:warm blood cardioplegia induction and terminal perfusion plus 4 C ST. Thomas hospital solution (STS)during ischemia;group 2: warm blood cardioplegia enriched with amino acid (L-asparte and L-glutamate 13 mmol/L each) and STS without amino acid (A.G.) and group 3:both warm blood cardioplegic solution and STS enriched with A. G..The result demonstrated that the cardiac function of animals in group 2 and 3 had a significantly better recovery after ischemic-re-perfusion. By the end of ischemia the content of myocardial ATP in group 3 was distinctly higher than that in group 1(P<0. 05), with the release of cardiac enzyme being the least. Myocardial ultra-structure almost remained intact before and after ischemia. Our experiment suggests that the cardioplegia arrest with warm blood and cold crystalloid solution enriched with amino acids could diminish the ischemia-re-perfusion injuries of the heart and enhance the effect of myocardial protection.

The study of myocardial protective effect of creatine phosphate sodium in liver transplant patients

Objective:To study the cardioprotective effectof creatine phosphate sodium by measuring perioperative myocardial enzymes of allogeneic liver transplant patients.Methods:The 26 cases of orthotopic liver transplant patients were randomly divided into control group and creatine phosphate sodium group,13 cases in each group.The creatine phosphate sodium group were given creatine phosphate sodium 30 mg/kg at the time of induction.The control group were given equal amount of N.S.All patients at six-phase of before surgery,after anesthesia,before anhepatic phase,anhepatic phase,new liver and the 12 hours after surgery extraction radial artery.The CK,CK-MB and cTnI activity was measured.Results:To compared with control group,creatine phosphate sodium group’s plasma CK,CK-MB and cTnI concentrations in before anhepatic phase,anhepatic phase,new liver and the 12 hours after surgery 4 phase are significantly lower(p<0.05).Conclusions:The creatine phosphate sodium has a protective effect on liver transplantation in patients with myocardial damage.

Cardioprotection of Shenfu Injection(参附注射液) against Myocardial Ischemia/Reperfusion Injury in Open Heart Surgery

Objective： To investigate the protective effect of Shenfu Injection （参附注射液, SFI） against myocardium ischemia/reperfusion injury （IRI） in mitral valve replacement （MVR） with cardiopulmonary bypass （CPB）. Metheds： Forty patients undergoing selective MVR were randomly assigned to the control group and trial Groups Ⅰ, Ⅱ,Ⅲ, and Ⅳ according to the different administrations of SFI, 8 patients in each group. The changes of systolic blood pressure （SBP）, mean blood pressure （MBP）, diastolic blood pressure （DBP） in each group were monitored, respectively. The recovering percentage of spontaneous heart beat, the heart rate （HR） and cardiac rhythm as well as the abnormal duration of ECG-ST segment were recorded after the restoration of heart beat. The serum concentration of cardiac troponin Ⅰ （cTnl）, malondialdehyde （MDA） and the activity of superoxide dismutase （SOD） were determined as well. Results： （1） The SBP, MBP and DBP values, the recovering rate of spontaneous heart beat, HR, ECG-ST, atrioventricular block and ventricular arrhythmia were significantly improved in group Ⅳ compared with any other groups. （2） Compared with the control group, the postoperative serum contents of cTnl and MDA were significantly decreased, but the activity of SOD was significantly increased in group Ⅳ. Cenclusiens： SFI had a certain protective effect against myocardium IRI. Moreover, better efficacy was seen with the administration of 1.5 mL/kg SFI into CPB priming fluid and pumping 1.5 mL/kg SFI via CPB as soon as the clamped aorta was unclamped.

Effect of ecdysterone on heteroptopic heart transplantation in rats

Objective： To investigate the protective effects of ecdysterone（EDS） on the allograft heart transplant model of rats. Methods： Fifty healthy Sprayue-Dawley（SD） rats were divided into donors and recipients randomly. Hearts were harvested and placed heterotopically into allogenic recipients. All animals were divided into three groups： sham-operation group（only opening and closing the abdomen, n=l 0）, EDS group（injected intraperitoneally with 20 mg/（kg · day） of EDS, n = 10）, and control group （injected intraperitoneally with normal saline, n = 10）. The pathological changes of myocardial tissue were analyzed by light microscopy and transmission electron microscopy and the levels of myocardial enzymes（GOT, LDH, CPK）, SOD, ET-1, NO, MDA in serum were measured. Tissue samples underwent the detection ofapoptotic cell death by in situ terminal deoxyribonucleotide transferase-mediated dUTP nick end labeling for apoptotic index（M） and also by immunohistochemistry method to study the expressions of Bcl-2 and Bax. Results： Pathological examination and transmission electron microscope observation showed greater myocardium damage in the control group. EDS group showed a decrease in the amount of myocardial enzymes, MDA, ET-1 and an increase in the levels of SOD, NO, compared to the control group. The A1 of EDS group became lower than that of control group, meanwhile the EDS group increased the expression of Bcl-2 and decreased the expression of Bax. Conclusion： EDS has protective effects on heteroptopic heart transplantation, which provides a new idea for myocardial protection in heart transplantation. However, the mechanism of its protective effect needs further research.

Protective Effects of Hyperpolarizing Cardioplegia with Pinacidil on Myocardium in Rats

Whether the ATP sensitive potassium channel opener pinacidil can provide myocardial protective effects in prolonged isolated global ischemic rat heart was investigated. On modified isolated rat working heart model, 40 hearts were divided into four groups randomly: Hyperpolarized arrest H K solution containing pinacidil (50 μmol/L) (P1 and P2) and depolarized arrest St. Thomas' solution (S1 and S2) subjected to 15 ℃ hypothermia, 60 min (P1 and S1) or 120 min (P1 and S2) of ischemia and 30 min reperfusion. The experimental indices included cardioplegic efficiency, cardiac function, coronary blood flow, myocardial enzyme release, myocardial water and ATP content. Hyperpolarized arrest provided significantly better recovery of cardiac function than depolarized arrest. Postischemic coronary flow and myocardial ATP content were higher. The arrest time of electro mechanical activities were longer than depolarized arrest. There were no differences among the groups in myocardial water contents. The hyperpolarized arrest solution containing pinacidil can provide a marked myocardial protective effect during prolonged hypothermic myocardial ischemia.

THE ACTION OF CAPTOPRIL ON SCAVENGING OXYGEN FREE RADICALS

The protective effect of captopril on ischemic myocardium was studied in 40 patients with congenital heart disease accompanied with pulmonary hypertention.Twenty of these patients received captopril 50 mg b.i.d.for three months preoperatively (Group A).The other 20 patients without pretreatment with captopril were used as controls (Group B).In Group A,the cardiac output increased and the pulmonary pressure decreased significantly in the first 24 hours postoperatively,indicating a high cardiac output with a low vascular resistance.The differences or CPK,CPKMB,LDH release between Group A and Group B were highly significant or siguificant from the end of operation to 24 hours postoperatively. Myocardial protection in the reduction of the release of CPK, CPK-MB, LDH might be attributed to action on scavenging oxygen free radicals.

Mechanism of the protective effects of noninvasive limbs preconditioning on myocardial ischemia-reperfusion injury

Background This study aimed at assessing the effect of noninvasive limb preconditioning on myocardial infarct size, and determining whether nitric oxide and neurogenic pathway play an important role in the mechanism of acute remote ischemic preconditioning （IPC）.Methods Forty Wistar rats were randomly divided into four experimental groups. In Group I , the rats underwent 30-minute occlusion of the left anterior descending coronary artery, and 120-minute reperfusion. In Group PL, the rats underwent four cycles of 5-minute occlusion and reperfusion of both hind limbs using a tourniquet before the experiment was continued as in Group I. In Group PL-N and Group PL-,, we administered L-nitro-arginine methyl ester （L-NAME） 10 mg/kg or hexamethonium chloride 20 mg,/kg intravenously, 10 minutes before IPC. Infarct size as a percentage of the area at risk was determined by triphenyhetrazolium chloride staining.Results There were no statistically significant differences in mean arterial pressure and heart rate among these groups at any time point during the experiment （ P〉0. 05 ）. The myocardial infarct size （IS） was decreased significantly in Group PL and Group PL-U compared with Group I , and the IS/AAR was 34. 5%± 7.6%, 35.9%±8.6% and58.5%±8.5%, respectively （P〈0.05）. The IS/AAR was 49.1%±6.5% in Group PEN, and there was no significant difference compared with Group I （P〉0. 05 ）.Conclusions Noninvasive limb IPC is effective in protecting the myocardium from ischemia reperfusion injury. Nitric oxide plays an important role in the mechanism of acute remote IPC, in which the neurogenic pathway is not involved.

远程预缺血的心肌保护机制

Remote myocardial preconditioning can protect myocardium. Some bioactive substances released from noncardiac tissues which suffer from ischemia and reperfusion protects the heart by neuronal and humoral paths. Preconditioning at a distance can attenuate myocardial intracellular acidosis and Ca2+ overload,reduce neutrophil and platelet infiltration, protect mitochondrial function and reduce free radicals. This method is simple to apply and have some clinical value. In order to safely apply this method to clinic, a further study on the remote myocardial preconditioning and its mechanism is necessary.

Passive graft perfusion in off-pump coronary artery bypass grafting

Background Myocardial protection during off-pump coronary artery bypass grafting （OPCABG） is a multifactorial problem in which maintaining stable systemic hemodynamics is very important. In this study passive graft perfusion （PGP） was applied to investigate the effect during and after OPCABG as evaluated by cardiac troponin I （CTnl） and hemodynamic indexes. Methods Thirty first-time patients underwent OPCABG under one surgeon. They were randomly divided into two groups： The passive graft perfusion group （PGP, n=15） received distal coronary perfusion during the anastomosis and immediate graft perfusion after the distal anastomosis. The control group, no graft perfusion group, （NGP, n=15） received no graft perfusion after the distal anastomosis. The results of the two protocols were evaluated by concentration of CTnl and hemodynamic indexes before induction and after operation. Results There were no statistically significant differences between these two groups in their perioperation parameters. The level of CTnl increased postoperatively, reached its peak at 6 hours （P〈0.05） and recovered by the 6 days postoperative. Compared with the control group the concentration of CTnl in the PGP group was significantly lower at 6 and 24 hours （P〈0.01）. Compared with the NGP group, cardiac index （CI） in the PGP group was higher at 12 and 24 hours after operation （P〈0.05）. The period of mechanical ventilation was significantly shorter in the PGP group than in the NGP group （P〈0.05）. Conclusion PGP can increase the flow to the myocardium and shorten the heart ischemia time, thus maintain stable systemic hemodynamics, supply a satisfactory CI after surgery and improve surgery outcome.

Clinical Study on Protective Effect of Ginaton on Ischemia-Reperfusion Injured Myocardium during Cardiopulmonary Bypass

Objective: To observe the myocardial protecting effects of Ginaton (Ginkgo biloba extract) on ischemic-reperfusion injured myocardium during cardiopulmonary bypass (CPB). Methods: Twenty patients selected undergoing mitral valvular replacement were randomly divided into two groups. Control group: 10 patients, intermittent intra-aortic infusion with cold St.Thomas solution during hypothermic CPB. Ginaton group: 10 patients, intermittent intra-aortic infusion with cold St. Thomas solution containing Ginaton (0.5 mg·kg -1). Changes of ultrastructure levels of adenosine triphosphate (ATP), malondialdehyde (MDA) and hemodynamic data were measured. Results: Hemodynamic parameters in the Ginaton group were maintained better than those in the control group. MDA in the control group was significantly elevated during ischemic-reperfusion (P<0.05), while in the Ginaton group, there were no obvious change. The levels of ATP and energy change in the Ginaton group were obviously higher than those in the control group at declamping aorta (P<0.05). The percentage of normal mitochondria and glycogen content were significantly higher in the Ginaton group than that in the control group at declamping aorta (P<0.05). Conclusion: Ginkgo biloba extract may provide a beneficial effect on myocardial protection in ultrastructural preservation, prevention of high energy phosphate depletion, reduction in free radicals production and improvement of myocardial function.

Relationship between ischemia duration and expression of heat shock protein 70 in ischemia-reperfusion canine hearts

Background Heat shock protein 70 （HSP70） has been shown to exert a protective effect in hearts subjected to ischemia-reperfusion and alleviate adverse effects of myocardial ischemia-reperfusion injury （MIRI）. However, little is known about the influence of ischemia time on HSP70 expression. The effects of ischemic duration on the content of HSP70 transcripts in ischemia-reperfusion myocardium were investigated in this study. Methods Male mongrel dogs underwent a 15- or 60-min occlusion of the left anterior descending coronary artery, followed by a 120-min reperfusion. Additionally, a sham-operation group was assigned. The animals were killed after 120-min reperfusion and the heart was quickly removed. The myocardium was examined pathologically by electron microscopy. HSP70 mRNA expressions both in intact and ischemic myocardium were measured by a semiquantitative reverse transcriptase-polymerase chain reaction （RT-PCR） method using complementary DNA normalized against the housekeeping gene β-actin. Results （1） No ultrastructural changes of microvessels and myocardial cells except for a slight loss of mitochondrial granules were noted in reperfusion myocardium from dogs in 15-min ischemia group. In 60-min ischemia group, endothelial cells of capillaries showed slight swelling, and the intercellular linking gaps of endothelial cells slightly widened. As for myocardial cells, intercellular, intermyofibrillar, and intermyofilament edemas were present. Besides, the fractures of a few myofilaments, the granule loss and swelling of mitochondria were also seen. （2） HSP70 mRNA expression level in both ischemia-reperfusion zone and intact myocardium was markedly higher in 15- min ischemia group than in sham-operation group （36.2 ± 6.5 vs 22.0 ± 4.0, P = 0.005; 29.8 ± 4.5 vs 22.2 ± 4.7, P = 0.050）. Compared with sham-operation group, however, no changes in mRNA HSP70 levels were seen in 60 min ischemia group （25.7 ± 7.5 vs 22.0 ± 4.0, P = 0.681; 28.5 ± 4.7 vs 22.2 ± 4.7, P = 0.118）. The ratio of HSP70 mRNA expression content in ischemia-reperfusion zone to that in intact myocardium in 15-min ischemia group was not significantly different from sham-operation group （1.22 ± 0.16 vs 1.01 ± 0.22, P = 0.233）, but remarkably higher than 60-min ischemia group （1.22 ± 0.16 vs 0.89 ± 0.17, P = 0.019）.Conclusions The change of HSP70 expression in ischemia-reperfusion myocardium is associated with ischemia time, that is, short duration ischemia promotes HSP70 expression, whereas long time ischemia does not. Furthermore, the HSP 70 expression changes consist with the protective extent of myocardial ultrastructures.