Dexamethasone pretreatment attenuates reperfusion arrhythmia in rats

AIM: To investigate the effect of dexamethasone (DEX) preconditioning on reperfusion arrhythmia. METHODS: 46 Sprague-Dawley rats were divided randomly into DEX and control (CON) group, the rats were pretreated with DEX or sodium chloride before their hearts were separated for Langendorff perfusion and for ischemia/reperfusion. The reperfusion arrhythmias were observed dynamically after 60 min reperfusion following 30 min ischemia. The expression of HSP72 in myocardium was examined by Western blotting and immunohistochemistry at reperfusion 60 min. The levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and the activities of Na+-K+-ATP ase, Ca2+-Mg2+-ATPase on myocardial plasma membrane were detected. RESULTS: Compared with control group, the accumulated points and persistence time of ventricular arrhythmia were reduced significantly in DEX group (P<0.05), the expression of HSP72 was significant upregulated (P<0.05), the level of MDA was reduced significantly, the activities of SOD, CAT, GSH-Px and Na+-K+-ATPase were significantly higher (P<0.05). CONCLUSION: Dexamethasone pretreatment markedly reduces the reperfusion ventricular arrhythmias in rats, which may be attributed to upregulation of HSP72, SOD, CAT, GSH-Px , Na+-K+-ATPase and inhibition of lipid peroxidation.     

Effect of Ginkgo biloba extract on the expression of c-fos and HSP70 following focal cerebral ischemic reperfusion in rats

AIM: To investigate the influence of Ginkgo biloba extract (GBE) on the expression of c-fos, heat shock protein 70 (HSP70) during focal cerebral ischemic reperfusion in rats. METHODS: The middle cerebral artery occlusion (MCAO) model described by Zea longa was used. Healthy Wistar rats were randomized to 4 groups. Immunohistochemistry, in situ hybridization and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) were used to detect the expression of c-fos gene, HSP70 and cell apoptosis at different reperfusion time points: 1, 6, 12, 24 hours and 3, 7 days after recirculation. RESULTS: The positive reactions of both c-fos and HSP70 were significantly increased at different reperfusion time in GBE-pretreated ischemia/reperfusion (IR) group than those in ischemia/reperfusion group (P<0.01) and the number of TUNEL-positive cells was reduced in GBE-pretreated IR group. CONCLUSION: The GBE induced the expression of c-fos, HSP70 and contributes to neuroprotective activities after cerebral ischemia.     

Extracellular signal regulatory kinases mediate the cardioprotection induced by monophosphoryl lipid A

AIM:To investigate the cardioprotective effects of monophosphoryl lipid A(MLA) and its molecular mechanisms.METHODS: In the ischemia/reperfusion(I/R) model of porcine hearts, the effect of MLA on myocardial infarct size was observed. The protein levels of extracellular signal regulatory kinases (ERKs) and heat shock protein (HSP) 86 were detected by using western blotting method. RESULTS: MLA pretreatment significantly limited the infarct size in the porcine hearts subjected to I/R. It is also found that MLA pretreatment upregulated the protein levels of HSP86 and ERKs. CONCLUSION: MLA pretreatment can attenuate I/R injury in porcine hearts. The protective mechanism might be associated with ERKs-induced upregulation of HSP86 synthesis.     

Effects of heat shock protein 70 on inflammation after hepatic local ischemia/reperfusion in rats

AIM:To study the effects of heat shock protein 70 (HSP70) induced by the heat stress pretreatment on inflammation after hepatic ischemia/resperfusion.METHODS:With the hepatic local ischemia/reperfusion model (IR group),heat stress pretreatment (H+IR group) and injecting quercetin before heat stress pretreatment (Q+H+IR group) were performed.The HSP70,intercellular adhesion molecule-1 (ICAM-1) and the myeloperoxidase (MPO) activity were detected.The levels of serum ALT and AST and histological changes of the hepatocytes were also observed.RESULTS:In H+IR group,the HSP70 expression was higher than that in other groups at each time point,after performing ischemia-perfusion,hepatic injury was slighter.The levels of serum ALT and AST were increased slightly (P<0.01).The expression of ICAM-1 and the changes of MPO activity increased and peaked respectively at 6 h and 12 h after reperfusion.However,they were lower in H+IR group than those in IR group and Q+H+IR group.CONCLUSION:The HSP70 induced by heat stress pretreament reduces the expression of ICAM-1 and the changes of MPO activity during hepatic ischemia-reperfusion,then hepatic injury is depressed from the inflammation.     

Effects of non-wounded ischemic preconditioning on ischemia-reperfusion injury in isolated rat hearts

AIM:To observe the protective effect of non-wounded ischemic preconditioning on ischemic/reperfusion injury in isolated rat hearts. METHODS: 25 male SD rats, weighting (250±30) g, were randomly divided into three groups: control group (C,n=8), anoxia/reoxygenation group (A,n=8) and non-wounded legs ischemic preconditioning group (N-WIP,n=9).Hearts were isolated from rats and perfused on a Langendorff apparatus with a normal Krebs-Henseleit buffer (saturation 95% O₂+5% CO₂) at a constant pressure (8.33 kPa) and temperature (37 ℃) in C group; Following 15 min equilibration, hearts were subjected to 15 min of global ischemia and 15 min reperfusion (37℃) in A group; Rats were subjected to non-wounded leg repeated-brief ischemic preconditioning, and then treated in procedure similar to A group in N-WIP group.The activities of superoxide dismutase (SOD) and Ca²⁺-Mg²⁺-ATPase, malondialdehyde (MDA) content of efflux from coronary vessel and myocardium, myocardium monophasic action potential and contractile force were measured before ischemia, 15 minutes after ischemia and 5, 15 minutes after reperfusion. RESULTS:Compared with A group, non-wounded legs ischemic preconditioning reduced the incidence of reperfusion arrhythmias (P＜0.05), decreased the content of MDA of myocardium (P＜0.01), enhanced the activities of SOD (P＜0.01) and stabilized myocardial membranous potential,the activity of Ca²⁺-Mg²⁺-ATPase and contractile function. CONCLUSION:These results indicate that non-wounded leg ischemic preconditioning has a protective effect on ischemia-reperfusion injury in isolated rat hearts. The mechanism may be related to the strength of antioxidation, the stability of Ca²⁺-Mg²⁺-ATPase activity and membranous structure in myocardium.     

Polydatin downregulates TLR4 expression in lung ischemia reperfusion injury in rabbits

AIM: To explore the influence of polydatin (PD) on Toll-like receptor 4 (TLR4) signal transduction pathway during lung ischemia reperfusion injury in rabbits. METHODS: Rabbit lung model of ischemia reperfusion (IR) injury was constituted in vivo. Thirty rabbits were divided into groups randomly: control (C), IR and PD group, respectively. The concentration of endotoxin (ET) in plasma was analyzed by end-point chromogenic assay. The protein expressions of TLR4, nuclear factor (NF)-κB p65 and heat shock protein 70 (HSP70) were measured by immunohistochemistry. The intracellular adhesion molecule-1 (ICAM-1) mRNA expression was detected by in situ hybridization histochemistry. The ultrastructural changes were observed by electron microscope. RESULTS: No significant difference of ET concentration in plasma between groups (all P>0.05) was observed. The protein expressions of TLR-4, NF-κB p65, HSP70 and ICAM-1mRNA in IR group were significantly increased as compared to C group and PD group, while those expressions in PD group were evidently higher than those in C group (all P<0.01). The lung pathological injuries in PD group were obviously alleviated as compared to IR group under electron microscope. CONCLUSION: It suggests that lung ischemia reperfusion releases endogenous ligands of TLR4 as HSP70, then activates NF-κB, promotes the release of mediators of inflammation such as ICAM-1. PD might have a protective effect on lung ischemia reperfusion injury by regulating TLR4 signal transduction pathway.     

Effects of mechanical stretch on electrophysiological characteristics of calcium preconditioning myocardium

AIM: To investigate the effects of mechanical stretch under simulated anoxia and reoxygenation conditions on action potential (AP) and effective refractory period (ERP) of calcium preconditioning (CPC) in isolated papillary muscles of guinea pig hearts. METHODS: The intracellular standard glass microelectrode technique was used, and effects of stretch (intensity: 200 mg) on AP and ERP were recorded and observed in CPC papillary muscles. RESULTS: After stretching was implied during anoxia, the reductions of Vmax, RP, APA, APD50, ERP and APD90 in CPC group were less than those in anoxia-reoxygenation (AR) group, and the CT in CPC group was less elongated. Moreover, after the papillary muscles were stretched during reoxygenated reperfusion, the decreases in Vmax, RP, APA, APD50 and ERP in CPC group were less than those in AR group, and the CT and APD90 in CPC group were less extended. Streptomycin inhibited the effect of stretch on AP and ERP in CPC group. CONCLUSIONS: Under simulated anoxia and reoxygenation conditions, papillary muscles in CPC group may have better tolerance to the same stretch than those in the AR. Furthermore, streptomycin (a blockade of stretch-activated ionic channels) may inhibit the effect of mechanical stretch on action potential changes in CPC papillary muscles.     

自由基清除剂对几种蔬菜衰老种子活力的影响

用外源自由基清除剂ＳＢＮ（１、２ｍｍｏｌ／Ｌ）和ＧＳＨ（０．００１、０．００５ｋｇ／Ｌ）浸种西瓜、甜瓜和萝卜衰老种子能显著促进其萌发，而ＡｓＡ（５、１０、１５ｍｍｏｌ／Ｌ）浸种效果不明显，上述处理要不同程度地提高衰老种子中ＣＡＴ和ＳＯＤ活性，降低Ｏ２＾－产生速率，减轻膜脂过氧化作用。     

Effect of limb ischemic postconditioning on brain focal ischemia and reperfusion injury in mice

AIM: To establish the mouse model in which the limbic ischemic postconditionning (LIPostC) enhances the tolerance against brain ischemia, and to investigate the effects of LIPostC on the ischemic extent and roles of heat shock protein 70 (HSP70) in ischemia and reperfusion injury. METHODS: The male Kunming mice were used in the study. The brain ischemia reperfusion (I/R) model was made by middle cerebral artery occlusion (MCAO). In the first test, the male mice were randomly divided into 9 groups (n=10): sham group, ischemia/reperfusion (I/R) groups (with ischemia for 0.5 h, 1 h,1.5 h and 2 h) and LIPostC+I/R groups (0.5 h+LIPostC,1 h+LIPostC,1.5 h+LIPostC,2 h+LIPostC). The reperfusion was performed after LIPostC for 24 h. After the neurologic deficit scores were evaluated, the brains were taken out to measure the infarct volume with TTC staining and to observe the pathological changes of cerebral cortex with HE staining. The neuronal apoptosis was determined by TUNEL. In the second test, the male mice were randomized into 4 groups (n=6): sham group, I/R group, LIPostC+I/R group and LIPostC+I/R+quercetin group (2 h ischemia). The neurological deficit scores were evaluated at 24 h after operation. The expression of HSP70 was determined by Western blotting.RESULTS: The duration of brain ischemia was related to the motor behavior and degree of brain injury. The longer the ischemic duration of the brain was performed, the more severe the pathological and behavioral changes were observed. The brain injury in 2 h MCAO mice was more severe than that in 1 h and 1.5 h MCAO mice (P<0.05). Compared to I/R group, each LIPostC group showed lower neurological score, less infarct volume and TUNEL positive neuron. The expression of HSP70 protein was increased and neurological functions were improved significantly in the mice with LIPostC. However, the neuroprotective role of LIPostC was attenuated by treating with quercetin, an inhibitor of HSP70.CONCLUSION: LIPostC promotes the expression of HSP 70, improves the neurological functions and attenuates the ischemia and reperfusion injury in MCAO mice. HSP70 produces a marked effect on the ischemic tolerance induced by LIPostC in MCAO mice.     

Effect of ischemic post-conditioning on myocardial mitochondrial function in isolated rat heart

AIM: To investigate the protective effect of ischemic post-conditioning on isolated rat myocardial mitochondrial function during ischemia/reperfusion, and to study the role of mitochondrial ATP-sensitive potassium channel (mitoK_ATP) in myocardial protection. METHODS: Sprague-Dawley male rats were randomized into 4 groups (n=8 in each group): control group (C), model group (M), ischemic post-conditioning group (IPO) and 5-hydroxydecanoate plus IPO group (5-HD+IPO). The hearts isolated from the SD rats were mounted on a Langendorff apparatus and started with a 20-minute perfusion for equilibration. In C group, the hearts went on perfusion for another 70 min after equilibration. In M group, 4 ℃ St. Thomas cardioplegic solution was administered prior to ischemia, followed by ischemia for 40-minute, and reperfusion for another 30 min. In IPO group, the hearts underwent 40-minute global ischemia after equilibration, then perfusion for 10 s and ischemia for another 10 s. The procedure was repeated 6 times before 28-minute reperfusion. In 5-HD+IPO group, the hearts were perfused with 5-HD (100 μmol/L in K-H solution) and treated as that in IPO group, then reperfusion for 23 min. The reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and respiratory function of myocardial mitochondria were measured at the ends of equilibration and reperfusion. RESULTS: (1) Compared with the data collected at the end of equilibrium, the MMP was obviously decreased at the end of reperfusion in all groups, The highest in C group. MMP in 5-HD+IPO group was markedly higher than that in IPO group and M group. MMP in IPO group was higher than that in M group. (2) In contrast to that at the end of equilibrium, ROS was obviously increased at the end of reperfusion in all groups. However, ROS was observably higher in M group than that in the other 3 groups, and ROS in 5-HD+IPO group was markedly higher than that in IPO group and C group. ROS in IPO group was higher than that in C group. (3) The respiratory function of mitochondria was obviously injured at the end of reperfusion in all groups. The arrangement of the mitochondrial respiratory function from the best to the worse was C group > IPO group > 5-HD+IPO group > M group. CONCLUSION: Ischemic post-conditioning attenuates myocardial reperfusion injury by maintaining the stability of MMP, decreasing the generation of ROS and preserving the respiratory chain function of mitochondria. The mitoK_ATP antagonist 5-HD can not completely block the myocardial protective effect of ischemic post-conditioning. Myocardial protective effect of ischemic post-conditioning may achieve by activating mitoK_ATP, meanwhile the other factors may also take part in the myocardial protective processes.     

Postconditioning of zacopride depresses ischemia/reperfusion-induced arrhythmias in rats

ATM: To investigate the effects of postconditioning of zacopride, a specific agonist of inwardly rectifying potassium channel (K_ir), on ischemia/reperfusion-induced arrhythmias and the involved electrophysiological mechanisms. METHODS: Langendorff-perfused SD rat hearts or anesthetized rats were subjected to coronary artery occlusion for 15 min followed by 15 min of reperfusion to induce ischemia/reperfusion arrhythmias. Zacopride was applied 3 min before reperfusion. Various arrhythmias were monitored and compared in different groups. The single rat ventricular myocyte was isolated by collagenase digestion. The effects of zacopride on hypoxia/reoxygenation-induced delayed afterdepolarizations (DADs) and ATP-sensitive potassium channel (K_ATP) were observed by the technique of whole-cell patch clamping. RESULTS: Post-conditioning of 0.1~10 μmol/L zacopride significantly prevented the hearts from reperfusion arrhythmias. During reperfusion, 0.1 μmol/L zacopride showed the maximum effect, with decreasing the number of premature ventricular beats (PVB), reducing the incidences of ventricular tachycardia (VT) and ventricular fibrillation (VF), and shorte-ning the duration of VT and VF (P<0.01). The postconditioning effects were partly reversed by 1 μmol/L BaCl₂(P<0.01), suggesting that the antiarrhythmic effect of zacopride was mediated by K_ir. In the in vivo study, 1.5~5 μg/kg zacopride had positive effects on reperfusion-induced VT and VF and negative effect on PVB. At the dose of 1.5 μg/kg, zacopride showed the most potent antiarrhythmic effect, which compared favourably with that of a classical antiarrhythmic agent, lidocaine. Furthermore, zacopride significantly inhibited hypoxia/reoxygenation-induced DADs (P<0.01). Zacopride had no effect on K_ATP.CONCLUSION: The inhibitory effect of zacopride on ischemia/reperfusion-induced arrhythmias is mediated by the activation of K_ir. Augmentation of K_ir cuvrent, thus diminishing the DADs, might be the critical mechanisms underlying postconditioning of zacopride.     

Effect of pretreatment with 11,12-EET on myocardial ischemia/reperfusion injury in rats

AIM: To examine the effect of pretreatment with low-concentration of 11, 12-epoxyeicosatrienoic acid(EET) on myocardial ischemia/reperfusion injury in rats. METHODS: After tracheotomy, myocardial ischemia/reperfusion was produced by occlusion and release of the left anterior descending artery(LAD) of the rats. Ischemic preconditioning(IP) was made by two times of ischemia(5 min)/reperfusion(5 min). The experiment was conducted in three groups: control,IP and pretreatment with 11,12-EET(6.24×10^-8 mol/L), and each group was subdivided into two subgroups:A,the rats were subjected to ischemia(10 min)/reperfusion(10 min) and arrhythmias during the whole periods were monitored; The rats in B were subjected to ischemia(60 min)/reperfusion(30 min) and arrhythmias, cardiac funtion and myocardial infarction size were documented. RESULTS: Both IP and pretreatment with 11,12-EET could protect the heart against arrhythmias, cardiac disfunction and myocardial infarction. CONCLUSION: Pretreatment with 11,12-EET had protective effect on myocardium in case of ischemia/reperfusion, which was similar to ischemic preconditioning.     

Ischemia reperfusion-induced proteomic changes in rat skeletal muscle

AIM: To investigate ischemia reperfusion (I/R)-induced proteomic changes in rat skeletal muscle. METHODS: Healthy male Wistar rats were randomly divided into two groups as follows (n=6): sham group and I/R group. I/R of right hind limb was induced by 4 h ischemia followed by 24 h reperfusion. The 2-DE was applied to separate the proteins extracted from skeletal muscle tissue at the end of experiment, followed by Coomassie Brillant blue R-250 staining. Computer image analysis was used to determine the differential expression of proteins between the two groups, and 7 protein spots expressed differentially were picked out and subjected to in-gel digest and MALDI-TOP for identification. RESULTS: 354±13 proteins were detected and the match rate was (78.7±1.4)%. 10 proteins displayed significant changes after I/R, of which, 6 proteins increased and 3 proteins decreased in expression. Moreover, 2 spots in I/R group were observed, only 1 spots of which in control. 5 proteins were identified after mass spectrometry. Mitochondrial aldehyde dehydrogenase (ALDH) precursor, heat shock 27 kD protein (HSP27), an unnamed protein product (increased in I/R group), α-actin (decreased in I/R group), and nuclear transport factor 2 (NTF-2) W7a mutant were found in I/R group. CONCLUSION: I/R injury induced differential proteomic changes in rat skeletal muscle. ALDH, α-actin and HSP27 expression, and NTF-2 mutation are involved in I/R injury.     

Protective effect of heat-shock pretreatment on rat ischemia-reperfusion myocardium

AIM:To investigate the changes of expression of P-selectin (Ps) in ischemia-reperfusion myocardium and to observe the effects of heat shock protein (HSP) on the expression of Ps and apoptosis. METHODS:Mature female Wistar rats (n=40) were divided into three groups at random. Under general anesthesia, the rats in heat-shock group were subjected to whole-body hyperthermia, and those in the other two groups were treated with anesthetic alone. Twenty-four hours later, the animals in heat-shock group and in control group were subjected to surgical operative ligation of coronary left anterior descending branch (LAD) for 1 h, then accepted reperfusion for 2 h. Those in sham operation group were also performed surgical operation without LAD ligation for 3 h. After operation, the CK-MB in blood serum, infarct size of left ventricles, HSP70, Bax, Bcl-2, Ps and apoptosis cells were measured. RESULTS:The amount of HSP70 in heat-shock group was significant higher than that in control group and in sham operation group (P<0.05). There was no difference between control group and sham operation group (P>0.05). Compared with control group, the infarct size, CK-MB, apoptosis cells, Bax and Ps in heat-shock group were significantly reduced (P<0.05). However, expression of Bcl-2 was similar (P>0.05). No expression of Ps in sham operation group was detected. CONCLUSIONS:HSP70 may reduce myocardial apoptosis during ischemia-reperfusion. One of the mechanisms is that HSP70 restraines the expression of Bax and Bax/Bcl-2. Ps plays an injurious role in ischemia-reperfusion myocardium. HSP70 is likely to restrain Ps from expression, which may be one of the mechanisms by which heat-shock pretreatment plays a protective role in ischemia- reperfusion myocardium.     

Role of apelin in rat myocardial ischemic preconditioning and ischemia/ reperfusion injury

AIM: To study the alteration and role of apelin in myocardial ischemic preconditioning and ischemia/reperfusion injury of rats.METHODS: Forty-five SD rats were randomly divided into three groups: ischemia/reperfusion group (IR),ischemia pre-conditioning group (IP) and sham operation group.ECG was continuously used to evaluate the score of arrhythmias.The protein levels of apelin-36 in myocardium and plasma were detected by radioimmunoassay.The expression of apelin was observed by immunohistochemistry.RESULTS: (1) The scores of arrhythmias in IP group (2.1±0.5) was only 58.3% of IR group (3.6±0.8) ( P<0.01).(2) The apelin-36 protein level of plasma and myocardium in IR group were respectively lower by 36.1% and 45.6% than those in SH group (P<0.01),and those in IP group were lower by 23.8% and 24.7% than those in SH group (P<0.01),but higher than those in IR group (18.9% and 38.5%,respectively,P<0.05).(3) The staining absorbance of apelin in IR,SH and IP group was (7.87±2.41),(22.53±2.54) and (14.23±2.15),respectively.There were significant differences between IR and SH (P<0.01) and between IP group and SH group (P<0.05).(4) The scores of arrhythmias in IP and IR were negatively correlated with the protein level of apelin-36 in myocardium (r= 0.847,P <0.01).CONCLUSION: The down-regulation of apelin-36 in the plasma and myocardium of rats indicates that apelin has an important role in myocardial ischemic preconditioning and ischemia/reperfusion injury.     

Effect of heat shock protein 70 expression induced by glutamine on vascular hyporeactivity in rats caused by LPS

AIM: To observe the effect of heat shock protein 70(HSP70) expression induced by glutamine on Escherichia coli lipopolysaccharides(LPS)-induced vascular hyporeactivity in rats.METHODS: Twenty four healthy male Sprague-Dawley rats were randomly divided into: the control group (n=8);LPS shock group (n=8);glutamine(Gln) treated group (Gln 0.75 g·kg-1 iv,n=8).6 h after LPS shock,phenylephrine (PE,0.5-2.5 μg·kg-1 ) was applied intravenously to all groups and the percentage increase in mean arterial pressure(MAP) was detected,respectively.The concentration-response curves of aorta rings were obtained by cumulative addition of phenylephrine (PE),and PE Emax,EC50 were calculated.The blood concentration of malondialdehyde (MDA),TNF-α and IL-6 were assayed in all groups 30 min and 360 min after LPS shock,respectively.The expressions of HSP70 from heart and aorta were also assayed after 6 h LPS shock.RESULTS: The MAP level induced by PE significantly decreased by 51.4% in LPS shock group compared with the control (P<0.05).However,PE induced MAP level increased by 17.5% in Gln group compared with LPS shock group (P<0.05).Emax and EC50 to PE were significant reduced in LPS shock group compared with control group (P<0.05),but significantly improved in Gln group (P<0.05).The expressions of HSP70 from heart and aorta were much higher in Gln group than those in LPS shock group (P<0.05).The blood concentrations of TNF-α,IL-6 and MDA were much lower in Gln group than those in LPS shock group.CONCLUSION: Glutamine effectively improves α-adrenergic receptor-mediated vascular reactivity through inducing the expression of HSP 70,reducing inflammatory cytokine release and peroxide biosynthesis in LPS shock.These results suggest that glutamine have potential beneficial therapeutic effect for septic shock patients.     

Effects of Shenmai injection on acute myocardial ischemia/reperfusion injury in rats

AIM: To observe the effect of Shenmai injection on the acute myocardial ischemia/ reperfusion injury in rats. METHODS: The left-anterior coronary artery was ligated for 10 minutes and then loosed for 15 minutes to establish the animal model of acute myocardial ischemia/reperfusion injury. During the process, electrocardiogram was traced continuously to observe the arrhythmia caused by reperfusion. The levels of SOD, MDA, Na⁺, K⁺-ATPase and Ca²⁺ -ATPase in ventricular myocardium were measured. The mitochondria was observed through electron microscope. RESULTS: Shenmai injection decreased the incidence of arrhythmia caused by reperfusion and shortened its duration. Shenmai injection improved the activity of SOD, Na⁺, K⁺-ATPase and Ca²⁺ -ATPase, decreased the content of MDA in myocardium and relieved the injury of mitochondria. CONCLUSION: Shenmai injection had a protective effect on acute myocardial ischemia/reperfusion injury in rats. The mechanism may be related to relieving the injury caused by oxygen free radical and calcium overload.     

Effect of diazoxide postconditioning on cardiac function and mitochondrial cardiolipin in isolated rat heart

AIM: To investigate the effect of diazoxide (D) postconditioning on Cardiac function and mitochondrial cardiolipin in isolated rat heart and to explore the protective effect of ATP sensitive potassium channel on diazo-xide postconditioning myocardium. METHODS: The myocardial ischemia/reperfusion injury model in isolated rat hearts was established by Langendorff apparatus. The isolated rat hearts were randomized into 4 groups (n=8): control group (control), myocardial ischemia/reperfusion injury group (I/R), diazoxide postconditioning group (I/R+D), 5- hydroxy decanoic acid (5-HD) plus diazoxide postconditioning group (I/R+5-HD+D). The hearts in each group were started with 20 min perfusion for equilibration. The hearts in control group perfused for 70 min; The hearts in I/R group was global ischemia for 40 min after ischemia reperfusion at 4 ℃ ST. Thomas cardioplegia, then reperfusion for 30 min; The hearts in I/R+D group were treated with diazoxide (50 μmol/L) in K-H perfusion for 5 min after global ischemia for 40 min, then reperfusion for 25 min; The hearts in I/R+5-HD+D group were treated with 5-HD (100 μmol/L) in K-H perfusion for 5 min before diazoxide postconditioning, then reperfusion for 20 min. The heart rate, coronary outflow volume, heart function, myocardial enzymes and myocardial mitochondrial cardiolipin at the end of perfusion in each group were determined. RESULTS: Compared with control group and I/R+D group, the heart rate, the concentration of heart phospholipid and the coronary outflow volume were reduced, the heart function was significantly impaired the contents of myocardial enzymes were increased in I/R group. However, no significant difference between I/R group and I/R+5-HD+D group was observed. CONCLUSION: The diazoxide postconditioning protects the myocardium by increasing mitochondrial cardiolipin content, reducing the release of myocardial enzymes, improving heart function and reducing myocardial reperfusion injury. The myocardial protective effect of diazoxide is completely blocked by 5- hydroxy decanoic acid.     

Role of nitric oxide in ischemia/reperfusion injury and ischemic preconditioning

AIM: To clarify the role of nitric oxide(NO) in ischemic preconditioning(IP) and its effects on apoptosis. METHODS: Seventy-two male Wistar rats were divided into the following six groups:ischemia/reperfusion (IR) group,IP group,IR+L-arg group,IP+L-arg group,IR+L-NAME group and IP+L-NAME group,The following changes were measured:cardiac hemodynamic parameters,infarct size,PMNs counting myocardial MPO activity and TUNEL staining.RESULTS: ①L-arg significantly attenuated ischemia/reperfusion-induced heart injury,reduced PMNs infiltration and cardiomyocyte apoptosis.②L-NAME also significantly reduced infarct size,PMNs infiltration and cardiomyocyte apoptosis compared with IR group,however,L-NAME aggravated ischemia/reperfusions-induced cardiac functional injury.③L-arg or L-NAME did not significantly alter the protective effect of ischemic preconditioning. CONCLUSION: Increased production of endogenous NO before prolonged ischemic period can protect hearts and inhibit apoptosis.L-NAME can inhibit iNOS activity and ONOO^- production in reperfusion period to protect heart.     

Effect of ERK1/2 on ischemic preconditioning in diabetic rat hearts

AIM: To test the effect of ERK1/2 on ischemic preconditioning (IPC) in diabetic rat hearts. METHODS: The diabetic rat model was made with alloxan. After eight weeks, 24 rats were divided into 4 groups: non-diabetic IPC rats (group A); non-diabetic non-IPC rats (group B); diabetic IPC rats (group C); diabetic non-IPC rats (group D). ECGⅡ lead, left ventricular development pressure (LVDP), and first derivative of LVDP (±dp/dtmax) were recorded. Myocardial phosphorylation of extracellular signal regulated kinases1/2 (ERK1/2) was detected by Western-blotting. RESULTS: (1) The ventricular arrythmia score was significantly lower in group A than that in group C (P<0.01). (2) LVDP and +dp/dtmax % were significantly higher in group A than those in group B and group C (P<0.01). -dp/dtmax% was significantly higher in group A than that in group B. (3) Phosphorylation of myocardial ERK1/2 was significantly higher in group A than those in group B and group C. CONCLUSIONS: IPC reduced the severity of ischemia/rerperfusion- induced arrhythmias, improved cardiac function in non-diabetic rats. However, such beneficial effects of IPC were not observed in diabetic rats. The attenuation of cardioprotection by IPC in diabetic animals may be due to the decrease in the activation of myocardial ERK1/2.