Rat urotensin-II-induced main pulmonary artery contractions are mediated by MAPK

AIM: To investigate rat Urotensin-II(rat U-II)-induced vasoconstriction of rat main pulmonary arteries and the role of mitogen-activated protein kinase(MAPK). METHODS: The main pulmonary artery was dissected from the male Sprague-Dawley rats and artery ring width was 3-4 mm. Concentration-response curves were generated to rat U-II(0.03 nmol/L-30 nmol/L).Inhibitor of MAPK, PD 98059(0.1 μmol/L-10 μmol/L) were added into the medium after rat U-II(30 nmol/L)induced vasoconstriction had reached plateau to construct the relaxant concentration-response curves and their EC₅₀ and E_max. RESULTS：Rat U-II was a potent vasoconstrictor of isolated rat main pulmonary arteries [EC₅₀=7.95±0.40, E_max=(14.28±6.34)% of the response to 60 mmol/L KCl]; PD 98059 caused concentration-dependent relaxations of rat U-II precontracted arteries [EC₅₀=5.91±0.45, E_max=(81.39±13.65)%]. CONCLUSION: Rat U-II was a potent vasoconstrictor of rat main pulmonary arteries and this response was mediated through MAPK.     

Changes in monoamine oxidase activity during thrombotic cerebral ischemia and protection mechanisms of ginkgolide B in tree shrews

AIM:The present study was designed to examine changes in monoamine oxidase (MAO) activity during cerebral ischemia and whether ginkgolide B's brain protection challenges with inhibiting monoamine oxidase. METHODS: The focal thrombotic cerebral ischemia was formed by photochemistry-induced in tree shews.MAO activities in different areas which include ischemic,core, penumbra and contralater and serum, were tested by enzyme color-compared way. The protein contents in different area above was examined by amino acid autoanalytic apparatus. RESULTS:MAO activities in ischemic core in different group were much lower than that in the sham operation group and contralatetral areas, with its peak at seventy-two hours after occlusion, but that in penumbra and serum ascended. There were significant differences in MAO activities between ischemic group and control (P＜0.01). In ginkgolide B(GB) group, the MAO activities in all areas but not in core descended, significant differences(P＜0.01) between in GB group and in twenty-four hours after occlusion. Changes in MAO activity was consistent with alterations of brain proein content(r=0.81,P＜0.05). CONCLUSION:The changes in monoamine neurotransmitters in core and penumbra considerably depend on the alterations of MAO activities after thrombotically cerebral ischemia. Probably, protective effects of GB on ischemic neurons is related to its acting as antagonist of platelet activating factor and regulator of monoamine oxidase.     

The mechanism of neuronal injury and repair after focal cerebral ischemia

AIM:To explore the mechanism of neuronal injury and repair by investigating the expression of caspase-3 and apurinic/apyrimidinic endonuclease (APE/Ref-1) after focal cerebral ischemia. METHODS:A model of middle cerebral artery occlusion in rats was performed. The expression of caspase-3P₂₀ and APE/Ref-1 was examined by immunohistochemistry staining, TUNEL was applied to detected DNA damage, and double labeling with TUNEL and APE/Ref-1 was used to determine the relationship between APE/Ref-1 and DNA damage. RESULTS:The active subunit P₂₀ of caspase-3 was predominantly expressed within ischemic penumbra. The peak time of caspase-3P₂₀ positive cells preceded the appearance of TUNEL. With aggravation of cerebral ischemia, APE/Ref-1 immunoreactive cells in penumbra were significantly decreased. CONCLUSION:The activation of caspase enzymatic cascade following cerebral ischemia leads to degradation in DNA, meanwhile, decrease in DNA repair molecules or the failure of DNA repair may deteriorate the course.     

Effects of ginkgolide B on glial fibrillary acidic protein expression after thrombotic cerebral ischemia in tree shrews

AIM: The present study was designed to examine the changes in glial fibrillary acidic protein (GFAP) expression during cerebral ischemia and the effects of ginkgolide B on GFAP expression. METHODS: The focal thrombotic cerebral ischemia was formed by photochemistry-induced in tree shrews. GFAP stained by ABC immunohistochemistry and absorbance were measured with image analyze system. RESULTS: GFAP expression in astrocytes increased significantly (P<0.01) at 24 h and kept in higher level at 72 h (P<0.01) within penumbra after focal cerebral ischemia. GFAP expression declined when the animals were given GB at 6 h after thrombotic cerebral ischemia. CONCLUSIONS: Neuronal necrosis resulted in GFAP expression in astrocytes after local cerebral ischemia and GB protected neurons by antagonizing PAF receptor and inhibiting GFAP expression.     

Effects of hyperglycemia and cerebral ischemia on VEGF expression in different subfield of cerebral cortex in tree shrews

AIM: To observe the changes of VEGF expression in different subfield of brain in tree shrews during hyperglycemia and focal cerebral ischemia, in order to explore the relationship between cerebral ischemia, hyperglycemia and VEGF. METHODS: High blood glucose in tree shrews was induced by intraperitoneal injection of streptozotoctin. Focal cortical thrombotic cerebral ischemia was induced by photochemical method in tree shrews. At 4 h, 24 h and 72 h after cerebral ischemia, the histopathological changes and hippocampal neuronal density were examined. VEGF expressions in the ischemic core, penumbra and contralateral cerebral cortex were detected by immunohistochemistry technique at different times after cerebral ischemia. RESULTS: The results of histopathological study showed that there was infarction zone in the exposured cerebral cortex at 4 h after photochemical reaction, and the damage was most severe at 24 h, subsequently accompanied with the glia multiplication and rehab reaction at 72 h. The animals in hyperglycemic ischemic group suffered from greater neurological lesion than the normoglycemic stroke animals, especially at 24 h (P<0.01) and 72 h (P<0.05) after cerebral ischemia. Immunohistochemical analyses of VEGF expression revealed that it started to increase at 4 h after brain ischemia in the penumbra, reached a peak at 24 h, and weakened at 72 h. The stimulated VEGF production was also observed in hyperglycemic only group. When hyperglycemia and brain ischemia were combined, the VEGF expression was higher than that in hyperglycemic only group (P<0.05). Compared to normoglycemic ischemic group, no additivity of the effects of hyperglycemia combined with brain ischemia was observed. CONCLUSION: (1) The model of experimental hyperglycemia and cerebral ischemia is replicated successfully by applying the method combined in vivo injection of streptozotocin in the lower primate tree shrew with thrombotic focal cerebral ischemia. (2) This study shows that hyperglycemia aggravates the focal cerebral ischemia damage. (3) Cerebral ischemia and hyperglycemia both can independently up-regulate VEGF expression, but there is no additional increase in VEGF expression when hyperglycemia combined with brain ischemia is applied.     

Study on the binding capacity of IgA1 from patients with IgA nephropathy to human mesangial cells

AIM: To examine and compare the ability of serum IgA 1, from both the patients with IgA nephropathy(IgAN) and the healthy control, to bind to human mesangial cells(HMC). METHODS: Serum IgA was isolated with jacalin column, heated to aggregated form(IgA₁) and labeled with [¹²⁵I]. Binding capacity of IgA₁ to primary HMC was evaluated by radioligant binding assay, specificity of binding was determined by competitive inhibition, and relative affinities was compared by cross competitive inhibition. RESULTS: Both IgA₁ from normal control and patients with IgAN bound to MC in a dose-dependent, saturatable manner, but the binding of IgA₁ from patients was saturated at approximately 200 pmol while that from healthy was at 400 pmol. The Scatchard analysis revealed a Kd of(8.9±2.1)×10^-8 mol/L for patient' s IgA₁ versus(4.3±1.2)×10^-7mol/L for normal IgA₁(P<0.05). Competition inhibition showed that both serum albumin and IgG could not block the binding of IgA₁ to HMC while mIgA 1 could partially block that. Cross competition inhibition demonstrated that patient' s IgA₁ blocked normal IgA₁ binding significantly(P<0.01), however, normal IgA₁ was unable to inhibit the binding of patient' s IgA₁. CONCLUSIONS: ①There are IgA binding proteins or receptors on mesangial cells. ②IgA₁ from patients with IgAN has a higher binding capacity than that from healthy.     

Effects of peripheral-type benzodiazepine receptors in platelet membrane on patients with depression after first attack of cerebral infarction

AIM：To evaluate the changes of peripheral-type benzodiazepine receptors (PBRs) in platelet membrane in post-stroke depression (PSD) patients and to investigate the effects of PBRs on PSD. METHODS：Forty-three patients with PSD, fifty-nine patients with first-ever cerebral infarction and fifty-six healthy volunteers participated in this study. Platelet membrane in venous blood was prepared. Binding assay of the radioactive PBRs antagonist ［3H］PK11195 to platelet membrane was performed. RESULTS：A significant difference of ［3H］PK11195 binding was found among the 3 groups (P<0.01). Compared with the healthy volunteers ［(298.2±25.1） pmol/(g protein)］, a highly significant increase in ［3H］PK11195 binding was observed in platelet membrane in the patients with first attack of cerebral infarction ［(1 410.8±41.4） pmol/(g protein), P<0.01］. Compared with the patients with first attack of cerebral infarction, a significant reduction in ［3H］PK11195 binding was detected in platelet membrane in the patients with PSD ［(361.7±30.6) pmol/(g protein), P<0.01］. In the patients with PSD, no significant difference of ［3H］PK11195 binding was found between men and women (P>0.05). ［3H］PK11195 binding was related to the score of Hamilton depression rating scale (r=-0.44, P<0.01) but not to the duration of cerebral infarction (r=0.27,P>0.05). CONCLUSION:PBRs binding activity in platelet membrane decreases in the patients with PSD and affects the degree of depression.     

The application of DWI and ADC mapping in acute cerebral infarction and basis of pathophysiology

AIM:To study the roles of isotropic diffusion weighted imaging(DWI)and apparent diffusion coeficient(ADC)mapping in diagnosing early cerebral infarction.METHODS:21 patients with cerebral in farction (8hyperacute,13 acute)were imaged with both convent ional MRI and single-shot echo-planar isotropic diffusion weighted imaging.Among them 12 pat ients had CT scanning simultaneously within 24 hours after onset.The positive rate of early in farction was comparted on CT,T₂WI and DEI.The change of the infarct lesion in DWI and T₂WI was also analysed.The av erage ADC,relat ive ADC(rADC)and the ADC from center to periphery of the lesion were calculated.RESULTS:8 hypera cute cerebral ischemic regions were revealed at DWI and ADC mapping,but CT and conventional MR were not.Hyperacute and acute infarcts appeared as areas of hyperintensity on DWI,and their average ADC was significantly depressed comparted with homologous contralateral tissue(0.698±0.104)×10^-3mm²/s vs(0.990±0.161)×10^-3mm²/s(P<0.01).ADC value in 21 hypera cute had gradient sign.CONCLUSION:Isotropic diffusion weighted imaging and ADC mapping have greater senstitivity for acute and hyperacute cerebral infarction than conventional MRI and CT,and may be used to defined the core and penumbra of ischemic lesion.     

Effects of bFGF on neuronal apoptosis and fractalkine expression in cerebral ischemia/reperfusion rats

AIM: To study the effects of basic fibroblast growth factor (bFGF) on neuronal apoptosis and fractalkine expression in ischemic penumbra after cerebral ischemia/reperfusion in rats.METHODS: Thirty-six rats were randomly divided into 3 groups: sham operation group, ischemia/reperfusion group and bFGF group. The model of middle cerebral artery occlusion was established by the method of intraluminal filament blockage. The middle cerebral arteries were blocked for 1 h and then reperfused for 24 h. Neurological performances of all rats were scored with Bederson's standard. The brain tissues of the rats were stained and the average infarct volume was calculated. TUNEL method was used to determine the number of apoptotic neurons, and the expression of fractalkine was detected by the method of immunohistochemistry.RESULTS: The score of neurological performances in bFGF group was 2.23±0.59, lower than that in ischemia/reperfusion group (3.18±0.65). The number of apoptotic neurons in bFGF group (13.22±1.35) was lower than that in ischemia/reperfusion group (17.28±1.01, P<0.05), which was the lowest in sham operation group (0.91±0.65). Compared with sham operation group, the expression of fractalkine in ischemia/reperfusion group was decreased. The expression of fractalkine in bFGF group was mainly higher than that in ischemia/reperfusion group (P<0.05).CONCLUSION: Up-regulation of fractalkine may be one of the molecular mechanisms of bFGF to protect neurons against ischemia/reperfusion injury.     

Protective effect of magnesium on brain with acute ischemia and reperfusion injury

AIM: To dynamically observe the protective effect of magnesium on the brain with ischemia and reperfusion injury in the middle cerebral artery occlusion (MCAO) rat model using the device of laser Doppler flowmetry (LDF) .METHODS: Twenty-four Sprague-Dawley male rats (280-300 g) were used to establish MCAO model with the conventional line-embolism method.The rats were divided into 4 groups according to the initial time of peritoneal injection of magnesium sulfate (MgSO₄).The rats in MgSO₄ groups were treated with 25% MgSO₄ at 160 mg/kg at time points of 20 min, 30 min and 40 min after ischemia.The rats in control group were treated with the same volume of normal saline.The real-time fluctuation of the local cerebral blood flow (CBF) was dynamically monitored by LDF.The degree of nervous functional defect was evaluated by calculating the neurological impairment score of the rats after suffered from 2 h ischemia and followed with 24 h reperfusion.All the rats were killed with an end breaking method, and the volumes of brain infarction were evaluated by TTC staining at the brain slices obtained by autopsy.RESULTS: The fluctuating features in 3 MgSO₄ treatment groups were as follows: when reperfusion began, the local CBF appeared and increased smoothly, then approached to its baseline step by step, and kept at the stable level in the whole reperfusion period.The CBF in control group fluctuated sharply in the whole reperfusion period associated with the heart beating, which was significantly different from those in MgSO₄ treatment groups.The average volume of brain infarction in MgSO₄ treatment groups was 26.5%, 36.5% and 24.5%, respectively, and was 54.0% in control group.The local nervous defect scores in MgSO₄ treatment groups were 5.670±1.003, 8.670±1.211 and 7.170±1.472, respectively, and was 11.170±0.983 in control group.CONCLUSION: Vasomotor functional improvement might be one of the protective mechanisms of magnesium on the brain with cerebral ischemia and reperfusion injury in acute ischemic stroke.     

Effect of Jiere Xingshen Injection on cAMP,IL-1β content in hypothalamus of ET febrile rabbits

AIM: The effects of Jiere Xingshen(JRXS) Injection on cAMP, IL-1_β content in hypothalamus (HP) of endotoxin(ET)-induced feverish rabbits were studied. METHODS: The ET-induced fever model was established in rabbits and the cAMP content in hypothalamus (HP) and csf, IL-1_β content in HP were determined by radioimmunoassay following intravenous infusion of JRXS. RESULTS: In ET group, the ΔT[(0.40±0.11)℃], TRI₁(1.78±0.79), cAMP content in HP[(2.90±0.40)nmol/g], cAMP content in csf[(0.40±0.11)nmol/L)], IL-1_β content in HP[(6.08±0.79)ng/g] were higher than that of NS and JRXS+ET group (P＜0.01). In JRXS+ET group, the ΔT[(0.10±0.10)℃], TRI₁(0.36±0.64), cAMP content in HP[(1.37±0.27)nmol/g], cAMP content in csf[(14.4±3.69)nmol/L)], IL-1_β content in HP[(2.90±0.37)ng/g] were very close to that of NS group but lower than that of the ET group (P＜0.01);The cAMP content in HP and csf, IL-1_β content in HP paralleled with the fluctuation of temperature. CONCLUTION: JRXS Injection has significant inhibitory effect on ET-induced fever by inhibiting cAMP and IL-1_β production in hypothalamus.     

Effect of cholecystokinin-octapeptide on focal cerebral ischemia/reperfusion injury in rats

AIM:To examine the effect of cholecystokinin-octapeptide (CCK-8) on focal cerebral ischemia/reperfusion injury and its underlying mechanisms.METHODS:By using the suture model of focal cerebral ischemia and reperfusion, the effects of intracerebroventricular (icv) injection of CCK-8 and proglumide, nonselective CCK receptors antagonist, on the infarct size, regional cerebral blood flow (rCBF), and the levels of nitric oxide (NO), malondialdehyde (MDA) were observed in different brain regions of rats subjected to 1 h focal cerebral ischemia followed by 24 h reperfusion.RESULTS:(1) pretreatment with different doses of CCK-8 (0.3 μg,1.0 μg,2.0 μg or 4.0 μg) could attenuate the infarct size, but the statistically significant effects of CCK-8 were obtained only at the doses of 1.0 μg and 2.0 μg(P＜0.05). The neuroprotective effects of CCK-8 were blocked by pretreatment with proglumide. Administration of proglumide alone could worsen the ischemia/reperfusion injury. (2) CCK-8 (1.0 μg) inhibited the increase in NO, MDA levels in the ischemic core, and also inhibited the increase in NO level in the ischemic penumbra. The rCBF in the CCK-8 group was significantly higher than the normal value at 24 h after reperfusion (P＜0.05).CONCLUSIONS:These results suggest that both endogenous and exogenous CCK-8 alleviate focal cerebral ischemia/reperfusion injury. Such an action may be associated with inhibition of free radical-induced injuries and the improvement in rCBF.     

Mechanism of JAK2-STAT3 signaling pathway in ischemic postconditio-ning neuroprotection after cerebral ischemia in tree shrews

AIM: To investigate the regulatory effect of JAK2-STAT3 signaling pathway on the neuroprotection of ischemic postconditioning (IPoC) in tree shrews, and to explore the mechanisms of cerebral injury deterioration after inhibiting the JAK2-STAT3 pathway. METHODS: The model of thrombotic cerebral ischemia was induced by photochemical reaction in tree shrews and the IPoC was established at 4 h after ischemia followed by clipping ipsilateral common carotid artery on the ischemia side for 5 min (3 times). After IPoC and intracerebroventricular injection of AG490 (JAK2 inhibitor), the changes of cerebral infarction area were detected by TTC staining, and the histological and ultrastructural changes of cortical neurons were observed under light and electron microscopes, respectively. The protein levels of t-STAT3 and p-STAT3 in the cortical tissue were determined by Western blot. RESULTS: The neuronal pycnosis, mitochondrial swelling and vanish of the mitochondrial cristae were found in cortical cortex, and the infarction area was (24.78±3.30)% at 24 h after cerebral ischemia. Meanwhile, the phosphorylation level of STAT3 protein in the cortical tissue was significantly increased (P<0.01). The cortical neuronal damage and mitochondrial swelling were decreased after IPoC, the area of cerebral infarction was significantly reduced to (17.67±1.83)% (P<0.01), and the phosphorylation level of STAT3 protein was further increased (P<0.01). However, the neuronal damage was aggravated, the infarction area was expanded to (23.85±2.77)%(P<0.05) after treatment with AG490, and the phosphorylation level of STAT3 protein was also significantly reduced (P<0.05). CONCLUSION: IPoC may reduce cerebral injury by regulating the phosphorylation of STAT3 protein, and inhibition of JAK2-STAT3 signaling pathway may counteract the cerebral protective effect of IPoC and aggravate brain injury.     

Effect of Xin-Tong capsule on nitric oxide production and cGMP content of ventricular myocardium in rats with experimental myocardial ischemia

AIM:To study the effect of xin-tong capsule on nitric oxide production and cGMP content of ventricular myocardium in rats with experimental myocardial ischemia. METHODS:Rat model of acute myocardial ischemia induced by pituitrin was used in this study, and the lift of ST segment in ECG was used as the index of myocardial ischemia. The NO₂^-/NO₃^- and cGMP contents of ventricular myocardium in rats with myocardial ischemia were determined.RESULTS: NO₂^-/NO₃^- and cGMP contents in ventricular myocardium of myocardial ischemia were (486±59) nmol/g protein and (0.38±0.08) nmol/g protein, respectively, and markedly lower than those of control (P＜0.01). After administration of Xin-Tong capsule, contents of NO₂^-/NO₃^- and cGMP in ventricular myocardium of rats with myocardial ischemia were obviously elevated . In comparison with control, ST segment of ECG in rats with myocardial ischemia was lifted, and the lift peak of ST segment occur in 45 min after myocardial ischemia (P＜0.01). Pretreatment of Xin-Tong capsule can improve conditions of myocardial ischemia . CONCLUSION:Xin-Tong capsule can elevate the contents of nitric oxide and cGMP, and attenuate myocardial ischemia injury in rats.     

Inhibitive action of atorvastatin on NADPH oxidase-derived superoxide anion in ischemic brain tissue after reperfusion in rats

AIM: Reactive oxygen species, specifically superoxide anion formed during the early phase of reperfusion, augment neuronal injury. The present study tested the hypothesis that atorvastatin protects against cerebral infarction via inhibition of NADPH oxidase-derived superoxide anion in transient focal ischemia. METHODS: Transient focal ischemia was created in halothane-anesthetized adult male Sprague-Dawley rats by middle cerebral artery occlusion (MCAO). Atorvastatin (Liptor) was administrated subcutaneously 3 times before MCAO. Infarct volume was measured by triphenyltetrazolium chloride staining. NADPH oxidase enzymatic activity and superoxide anion levels were quantified in both ischemic core and penumbral regions by lucigenin (5 μmol/L)-enhanced chemiluminescence. The expression of NADPH oxidase membrane subunit gp91phox, membrane-translocated subunit p47phox and small GTPase Rac-1 were determined by Western blotting analyses. RESULTS: NADPH oxidase activity and superoxide anion levels increased following reperfusion and peaked within 2 h of reperfusion in the penumbra, but not in the ischemic core in MCAO rats. Atorvastatin pretreatment prevented this increases, blunted the expression of membrane subunit gp91phox and prevented the translocation of cytoplasmic subunit p47phox to the membrane in the penumbra 2 h after reperfusion. CONCLUSION: These results indicate that atorvastatin protects against cerebral infarction via inhibition of NADPH oxidase-derived superoxide anion in ischemic brain tissue after reperfusion partly.     

cPKCγ-HSP60 signal pathway participates in hypoxic preconditioning in mice

AIM: To identify the proteins interacted with conventional protein kinase Cγ (cPKCγ) which are involved in hypoxic preconditioning (HPC), and to investigate the role of cPKCγ-interacted heat-shock protein 60 (HSP60) in the development of HPC and ischemia (I).METHODS: Healthy male BALB/c mice were randomly divided into normoxia(Norm) and HPC groups. Based on whether middle cerebral artery occlusion (MCAO) was performed, the mice were divided into Norm+sham group, Norm+I group, HPC+sham group and HPC+I group ( all n=6). Immunoprecipitation, two-dimensional electrophoresis and mass spectrometry were applied to identify the proteins interacted with cPKCγ. The changes of HSP60 expression in the brain of the mice after HPC and MCAO were analyzed by Western blotting.RESULTS: The interaction of cPKCγ and HSP60 was confirmed by co-immunoprecipitation result. Compared with Norm groups, the expression level of cPKCγ-interacted HSP60 obviously increased in particulate fraction of cerebral cortex in HPC mice. In the MCAO ischemic animals, the level of HSP60 expression was significantly higher in ischemic core and penumbra in Norm+I group and HPC+I group than that in Norm+sham group. HSP60 expression in ischemic core was lower in HPC+I group than that in Norm+I group.CONCLUSION: cPKCγ-HSP60 signal pathway might be involved in the development of cerebral hypoxic preconditioning in MCAO mice.     

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.