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.     

Protective effect of delayed ischemic preconditioning on renal ischemia/reperfusion injury via induction of hypoxia inducible factor

AIM: To investigate the effects of delayed ischemic preconditioning on renal ischemia-reperfusion injury in mice and to study the role of hypoxia inducible factor 1α(HIF-1α). METHODS: Male C57/BL6N mice were randomly divided into 3 groups: sham operation group(sham), ischemia/reperfusion group(IR) and ischemic preconditioning group(IPC). Thirty-minute ischemia was induced by clamping renal bilateral pedicles followed by reperfusion in IR group. Fifteen-minute pre-ischemia was performed 4 days before IR in IPC group. Serum creatinine(Scr), blood urea nitrogen(BUN), kidney morphology and apoptosis were observed at different time points following reperfusion. The expression of HIF-1α in the renal tissues was evaluated by the methods of immunohistochemistry and Western blotting analysis. The mRNA expression of vascular endothelial growth factor(VEGF) and glucose transporter-1(Glut-1) was detected by real-time quantitative RT-PCR.RESULTS: Compared with IR group at 24 h following reperfusion, acute tubulointerstitial injury was significantly relieved in IPC group. The levels of Scr and BUN, and apoptosis of tubular epithelial cells were also decreased in IPC group. Nuclear expression of HIF-1α was higher in IPC group than that in IR group. The mRNA expression of VEGF and Glut-1, the target genes of HIF-1, was also increased significantly in IPC group. CONCLUSION: Delayed ischemic preconditioning attenuates both morphologic and functional injuries induced by renal ischemia/reperfusion. This protective effect may be related to the increased expression of hypoxia inducible factor.     

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。     

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.     

Intestinal ischemic postconditioning attenuates acute lung injury induced by intestinal ischemia/reperfusion in rats

AIM: Previous study has shown that brief period of repetitive superior mesenteric artery (SMA) occlusion and reperfusion applied at the onset of reperfusion, ischemic postconditioning (IPo), attenuates intestinal injury after intestinal ischemia/reperfusion (I/R). This study tested the hypothesis that IPo would attenuate intestinal I/R-induced acute lung injury which is comparable to ischemic preconditioning (IPC) and the brief period of postconditioning applied at the onset of reperfusion is critical to pulmonary protection by IPo. METHODS: Rat intestinal I/R injury was produced by clamping SMA for 60 min followed by 60 min of reperfusion. The rats were randomly allocated into one of five groups based upon the intervention (n=8): sham operation (sham): sham surgical preparation including isolation of the SMA without occlusion was performed; injury: there was no intervention either before or after SMA occlusion; ischemia preconditioning (IPC): the SMA was occluded for 10 min followed by 10 min of reperfusion before prolonged occlusion; ischemia postconditioning (IPo): 3 cycles of 30 s reperfusion-30 s reocclusion were imposed immediately upon reperfusion (3 min total intervention); delayed postconditioning (delay): clamping was completely released for full reperfusion for 3 min (the duration of the IPo algorithm), after which 3 cycles of 30 s occlusion and reperfusion were applied. RESULTS: Histological results showed severe damages in rat lungs in the injury group evidenced by increased lung wet/dry weight ratio and pulmonary permeability index, which was accompanied by increases in the levels of plasma TNF-α and IL-6, the pulmonary malondialdehyde (MDA), and the pulmonary myeloperoxidase (MPO) activity, and a decrease in superoxide dismutase (SOD) activity. IPo, not delayed IPo, significantly attenuated lung injury and improved the above variables, which was comparable to IPC. CONCLUSION: IPo at onset of reperfusion reduces acute lung injury induced by intestinal I/R, which may be mediated, in part, by inhibiting oxidant generation, filtration of neutrophils and releases of proinflammatory mediators. The early period of reperfusion in the rat model is critical to pulmonary protection by IPo. IPo may improve outcome in clinical conditions associated with intestinal I/R.     

Effect of 2, 3-butanedione monoxime (BDM) on myocardial protection in cold cardioplegia

AIM: The effects of BDM on isolated rat heart in cold cardioplegia were studied. METHODS: Rat heart were subjected to cold cardioplegia at 4℃ for 8, 18 and 24 h.Then each heart was perfused (90 cm H₂O) in Langendorff model at 37℃ for 40 min. In the high K⁺ group(n=24) the hearts were preserved in St.Thomas cardioplegic solution, in BDM group(n=24) hearts were preserved in K-H solution with BDM 30 mmoL/L. RESULTS: After 18 h, heart rate and the coronary flow in BDM group were significantly higher than in high K⁺ group(P＜0.05). Activity of Na⁺-K⁺-ATPase in cell membrane and in mitochondrial membrane in the BDM group was significantly higher than high K⁺ group(P＜0.01). After 24 h, all hearts in high K⁺ group were dead, but were alive in BDM group. CONCLUSION: Under given experiment conditions, BDM did enhance the tolerance to cold ischemia significantly. The results showed that BDM may become a useful agent for prolong the storage period of heart in cold cardioglegia.     

The alteration of extracellular sodium and potassium ionic activities of hippocampal neurons in epileptiform rats kindled by coriaria lactone

AIM and METHODS: The sodium ion Na⁺ and potassium ion K⁺ selective microelectrodes were used to measure changes of ionic activity of extracellular sodium and potassium( [Na⁺]_o, [K⁺]_o) in hippocampus and hippocampal slice during epieptic seizure induced by intrahippocampal microinjection of coriaria lactone(CL) in rats and perfusing hippocampal slice with CL. RESULTS:30 s, 1min and 2min after injection of CL into hippocampus, the [Na⁺]_o decreased 27.7 mmol/L, 50.3 mmol/L, 57.8 mmol/L respectively and the [K⁺]_o increased 2.3 mmol/L, 2.4 mmol/L, 2.9 mmol/L respectively compared with control values(P＜0.01). The [K⁺]_o returned to the control level 3min after local application of CL, but the[Na⁺] _o was still lower than that of control group(P＜0.01). The [Na⁺]_o and the [K⁺]_o were measured also in hippocampal silces and results are similar to those of experiments in vivo. CONCLUSION: The influx of Na⁺and the flux of K⁺occurred during epileptiform discharges of hippocampal neurons induced by administration of CL.     

Protective effect of pentoxifylline against spinal cord ischemia/reperfusion injury in rabbits

AIM: To investigate the protection of pentoxifylline against spinal cord ischemia/reperfusion injury.METHODS: Rabbits sustained spinal cord ischemia with 45 min cross-clamping of the infrarenal aorta. Groups were as follows: sham operation (n=8); ischemic control (n=20), receiving only vehicle; PTX A (n=20), receiving PTX before clamping and PTX B (n=20), receiving PTX at the onset of reperfusion. Rabbits were evaluated for hind-limb motor function with the Tarlov scoring system at 48 h. Serum was assayed with ELISA for TNF-α and spinal cords were harvest for MPO activity, histopathologic analysis and TUNEL staining. Immunohistochemistry was used for PECAM-1 and caspase-3 detection, and the numbers of necrosic and apoptotic neuron were counted at 12 h, 24 h, 48 h and 72 h of reperfusion. The necrotic and apoptotic neurons were also observed with transmission electron microscope.RESULTS: Improved Tarlov scores were observed in PTX-treated rabbits as compared with ischemic control rabbits at 48 h. The significant reductions of TNF-α in serum, activity of MPO, immunoreactivity of the PECAM-1 and caspase-3 were found in PTX-treated rabbits. The numbers of necrosic and apoptotic neuron were higher in PTX-treated rabbits than that in the ischemic control rabbits (P<0.05). No necrosic and apoptotic neuron were found in the sham operation group. CONCLUSION: PTX induces protection against ischemia/reperfusion injury in the spinal cord, thereby preventing both necrosis and apoptosis.     

Changes and significance of ATPase and free radical in aged rats with brain ischemia-reperfusion

AIM: To study the mechanism of brain ischemia-reperfusion injury from ATPase activity and free radical metabolism in aged rats. METHODS: The young rats (5 months) and the aged rats (more than 20 months) were divided into young control group(YCG), young model group(YMG), aged control group(ACG) and aged model group(AMG). The ATPase and SOD activities and the contents of MDA, Ca^2＋, Na^＋ and K^＋ were measured in the rats with 30 min brain ischemia followed by 60 min reperfusion. RESULTS: The Ca^2＋content in the AMG was higher than that in the YMG and the ACG. The Na^＋-K^＋-ATPase activity in the ACG was lower than that in the YCG,was lower in the AMG than that in the YMG. The Ca^2＋-ATPase activities in the YCG was higher than that in the ACG, was lower in the AMG than that in the YMG and was higher than the ACG's. The serum and brain tissue SOD activities in the ACG was lower than that in the YCG, was lower in the AMG than YMG 's. The serum and brain tissue MDA/SOD ratio in the AMG was higher than that in the ACG.CONCLUSION:The brain tissue ischemia-reperfusion injury was related with calcium overload and free radical injury.The pathological changes were obvious and had some characteristics in the aged rats compared with the young rats because of the brain t issue aging changes in ATPase,calcium content and free radical metabolism in the aged rats.     

Changes in concentration of amino acids in newborn rabbits brain with hyperbilirubinemia

AIM: To study whether the excitatory amino acids (EAAs)-triggered excitotoxicity contribute to the evolution of hyperbilirubinemia-associated brain injury. METHODS: Newborn rabbits with hyperbilirubinemia were decapitated and then, Na⁺-K⁺-ATPase activities, neurotransmitters and non-neurotransmitters concentration in brains were determined. RESULTS: It was found that the activities of Na⁺-K⁺-ATPase both in brains and cytomembrane and the amounts of glutamate (P<0.05) and aspartate (P＜0.01) in homogenated brains decreased significantly. But the amounts of GABA and non-neurotransmitters increased in model group. CONCLUSION: Extracellular abnormal accumulation of EAAs caused by bilirubin-induced energy failure in brain and the inhibition in Na⁺-K⁺-ATPase activity may result in excitotoxic neuronal death in newborn rabbits.     

Effects of ischemic preconditioning on hepatocyte apoptosis induced by hepatic ischemia-reperfusion in cirrhotic rats

AIM:To investigate the protective effect of ischemic preconditioning (IPC) on hepatic ischemia-reperfusion(I/R) injury in cirrhotic rats and its possible mechanism. METHODS:Hepatic I/R was induced by Pringle maneuver. The cirrhotic rats were randomized into three groups: Group A: before 30 min of ischemia, a short period of 5 min ischemia and 5 min reperfusion were given; Group B: before 30 min of ischemia, a short period of 10 min ischemia and 10 min of reperfusion were given; Group C: 30 min ischemia only. The serum alanine transferase (ALT), hepatic Fas-mRNA, caspase-3 activity and hepatocyte apoptosis were analyzed. RESULTS:The 7-day survival rate in the group A and B were 100%, respectively. However, it was only 62.5% in the group C. After 6 h of reperfusion, the ALT levels in both group A and B were significantly lower than that of in group C, P＜0.01. The ALT level of group A was also lower than that of group B, P＜0.01. The hepatic Fas-mRNA expression, caspase-3 activity and apoptotic hepatocyte in group A were significantly lower than those of in group C, P＜0.01. CONCLUSIONS:IPC has significant protective effect against hepatic I/R injury. An IPC with 5 min of ischemia and 5 min of reperfusion has the maximal protective effect. The protective mechanism of IPC against hepatic I/R injury is via down-regulation of Fas-mRNA expression, inhibiting caspase-3 activity and subsequently inhibiting hepatocyte apoptosis.     

The discovery of the interaction between augmenter of liver regeneration and Na+, K+-ATPase with yeast two-hybrid system

AIM:To screen the proteins interacting with human augmenter of liver regeneration (hALR) by yeast two-hybrid system and to study the mechanism of hALR action. METHODS:hALR bait plasmid was constructed by ligating the gene of hALR into pGBKT7, then transformed into yeast AH109. The yeast strain AH109 containing pGBKT7-hALR was mated with yeast Y187 containing human liver cDNA library plasmid. Diploid yeast was plated on SD/-trp-leu-his-ade (QDO) for screening and on QDO containing X-α-gal for further selection.The AD/library inserts were amplified by PCR and the PCR products were characterized by digesting with Sau3AⅠ and HaeⅢ restriction enzyme to eliminate the duplicates. After sequencing, the positive clones were analysed by bioinformatics. RESULTS:Several positive clones were obtaind. The sequencing and analysis shown that one of them is 669 bp DNA fragment encoding β subunit of Na⁺, K⁺-ATPase. The 224 bp 3'terminal DNA fragment is non-encoder region, and the 445 bp 5'terminal DNA encodes C-terminal 147 amino acid residues of Na⁺, K⁺-ATPase β subunit. CONCLUSION:The results of screening proteins using yeast two-hybrid system showed that hALR could interact directly with Na⁺, K⁺-ATPase in the yeast cell.     

Effects of prostaglandin I2 on mesenteric microcirculation and property of hemorheology in rabbits with renal ischemia/reperfusion injury

AIM: To explore the effects of prostaglandin I2 (PGI2) on mesenteric microcirculation and hemorheology during renal ischemia/reperfusion (IR) injury. METHODS: 36 rabbits were randomly distributed into the sham operated group (sham group)， renal ischemia/reperfusion injury group (IR group) and PGI2+IR group（PGI2 group）. IR group received clamping for 60 min followed by 120 min of reperfusion. A microcircular microscope image analysis system was used to study the changes of mesenteric microcirculation and hemorheology at 60 min of ischemia and 120 min of reperfusion, respectively， while the blood samples were obtained for the measurement of hemorheological indexes. RESULTS: ① In IR group during the period of renal IR， the number of adhesive leukocytes and microthrombus， hemorrhage and hemorheological indexes such as blood viscosity， plasma viscosity， blood reduction viscosity， hematocrit， erythrocyte aggregation index， erythrocyte sedimentation rate， erythrocyte sedimentation rate K and plasma fibrinogen were significantly higher， while microvascular diameters， blood flow velocity and erythrocyte deformation index were significantly lower compared with sham group (P＜0.01 or P＜0.05). ② PGI2 5-40 ng·kg-1·min-1) affected the indexes of mesenteric microcirculation and hemorheology to different extent. In 10 ng·kg-1·min-1 PGI2 group， the diameters of arteriole and venule， blood flow velocity， the number of adhesive leukocytes， microthrombus， hemorrhage and hemorheological indexes significantly changed， compared with IR group (P＜0.01 or P＜0.05). Except that microvascular diameters increased remarkably （P＜0.01）， others showed no significant difference compared to sham group （P＞0.05）. CONCLUSIONS: PGI2 ameliorates the disturbance of mesenteric microcirculation and hemorheology caused by renal IR injury with the best effect at 10 ng·kg-1·min-1.     

Protective effects of liposomes containing L-arginine,Se and taurine on intestinal ischemia-reperfusion injury in rats

AIM and METHODS:To study the protective effects of liposomes containing L-Arg,Se and taurine on intestinal ischemia-reperfusion injury in rats. Wistar rats were divided randomly into sham operated group,ischemia-reperfusion(I/R) group,pretreatment with liposomes group and treatment with liposomes at reperfusion group. In the experiments, superior mesenteric artery was clipped for 60 min, and then unclipped. 2 hours of reperfusion later, MDA content, T-SOD and Ca²⁺-Mg²⁺-ATPase activities in intestinal tissues were detected respectively, ultrastructure and bcl-2 expression in intestinal mucosa tissue were observed.RESULTS:MDA content in liposomes-treated group was less than I/R group (P＜0.01).The activities of T-SOD and Ca²⁺-Mg²⁺-ATPase in liposomes-treated group were higher than I/R group(P＜0.01). Bcl-2 staining was negative in I/R group, and was positive in liposomes-treated group (P＜0.01).There was no difference in above indexes between pretreatment with liposomes group and treatment with liposomes at reperfusion group(P＞0.05). CONCLUSION:Liposomes containing L-arginine, Se and taurine can protect intestine against ischemia-reperfusion injury in rats,which may be related to inhibiting lipid peroxidation, stabilizing internal circumstances and inducing bcl-2 protein expression.     

The protection of the hepatic ischemic preconditioning is concerned with the NO/ET-1 system

AIM: To study the relationship between the disturbance of nitric oxide/endothelin-1(NO/ET-1) and hepatic ischemia/reperfusion(I/R) injury as well as the regulation of NO/ET-1 system by hepatic ischemic preconditioning(IPC). METHODS: The changes of NO/ET-1 system and their relationship with hepatic I/R injury were compared between I/R group and IPC+I/R group in a rat hepatic I/R model. Two hours after reperfusion, the liver tissues were detected by RT-PCR to see whether there was inducible nitric oxide synthase (iNOS) mRNA expression. RESULTS:In the acute phase of hepatic reperfusion, the ratio of NO/ET-1 was reduced, which was due to a significant reduction of NO₂^-/NO₃^- (the metabolic product of NO) and significant elevation of ET-1 in the blood plasma. The content of ALT, AST, LDH and TNF-α in blood plasma, and of MDA in liver tissue were increased but ATP in liver tissue was reduced, the hepatic damage was deteriorated. The protection of the hepatic IPC was concerned with the elevation of the ratio of NO/ET-1 caused by the elevation of NO₂^-/NO₃^-, and reduction of ET-1 as well. There was no iNOS mRNA detected in the liver tissues.CONCLUSION: Hepatic I/R injury is related to the disturbance of NO/ET-1. The protection of the hepatic IPC in the acute phase might be conducted by its regulation of NO/ET-1 system. The cNOS rather than the iNOS generated the NO in this situation.     

Preconditioning with 3-nitropropionic acid induces rat cerebral ischemic tolerance and increases expression of glucose transporter 1 and glucose transporter 3

AIM: To explore the mechanism of 3-nitropropionic acid (3-NPA) preconditioning that induces cerebral ischemic tolerance in rats by affecting the expression of brain-type glucose transporters (GLUT1 and GLUT3) at mRNA and protein levels in cerebral tissues.METHODS: The male SD rats were used in the experiments and divided randomly into sham operation group (sham group, n=4), control group of 3-NPA preconditioning (3-NPA group, n=4), cerebral ischemia group (M group, n=16) and 3-NPA preconditioning group (IPC group, n=16). M group and IPC group were further divided into 4 subgroups according to the different reperfusion time(4 h, 12 h, 24 h and 48 h). All rats were killed at the corresponding time points. The cerebral tissues in the ischemic side (left) and coronal intermediate 1/3 of cortex were collected. The protein levels and mRNA expression of GLUT1 and GLUT3 were determined by Western blotting and RT-PCR. RESULTS: Compared with M group, the ischemic reperfusion and 3-NPA preconditioning induced the upregulation of GLUT1 and GLUT3 at protein levels with significant differences (F=5.848, P<0.05 and F=6.295, P<0.05, respectively), especially after ischemia-reperfusion for 48 h. The mRNA expression of GLUT1 in IPC group began to increase at 4 h, peaked at 48 h after reperfusion, with significant difference as compared to M group at the corresponding reperfusion time points in each group or sham group. In contrast, the mRNA expression of GLUT3 in IPC group increased at 24 h, and was the highest at 48 h as compared to cerebral ischemia group at the corresponding reperfusion time points or sham group.CONCLUSION: 3-NPA preconditioning increases the expression of GLUT1 and GLUT3 at protein and mRNA levels to maintain the energy supply in brain tissues, indicating a cerebral protective mechanism.     

Role of heme oxygenase-1 in the ischemic preconditioning of isolated rat heart

AIM: To investigate the influence of ischemic preconditioning on heart function, the activities of lactate dehydrogenase (LDH), malondialdehyde (MDA), and heme oxygenase-1 (HO-1) after ischemia/reperfusion in isolated rat heart. METHODS: The model of Langendorff was used in isolated rat heart perfusion. Ischemic preconditioning protocol: stopping perfusion for 5 minutes and reperfusion for 5 minutes, repeating three times. Ischemia protocol: stopping perfusion for 40 minutes and reperfusion for 20 minutes. Indexes of heart function were recorded in control M8, ischemia and reperfusion group (IR), and ischemic preconditioning group (IPC). The content of LDH of coronary effluent was measured. Moreover, the content of MDA and activity of HO-1 in myocardium were also measured. RESULTS: The recovery percentage of heart function in IPC group was significantly higher than that in IR group (P<0.01) and the activity of heme oxygenase-1 also increased significantly (P<0.05). CONCLUSION: The contents of LDH and MDA significantly decreased in IPC group compared with IR group. The increase in heme oxygenase-1 activity might be involved in the protective effect of ischemic preconditioning on ischemic/reperfused rat heart.     

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.     

Effects of 11, 12-EET and ischemic preconditioning on phosphorylated ERK and p38 MAPK during ischemia and reperfusion in rat myocardium

AIM: In order to study the relationship between the ERK and p38 MAPK activation and the protection of 11, 12-epoxyeicosatrienoic acid (11, 12-EET) and ischemia preconditioning (IP), the effects of 11, 12-EET and ischemic preconditioning on phosphorylated ERK and p38 MAPK during ischemia and reperfusion in rat myocardium were examined. METHODS: The rat heart was subjected to ischemia for 5 min by ligating the left anterior descending coronary artery followed by reperfusion for 5 min (two times) to undergo ischemia preconditioning. The rats were divided into 5 groups: (1) control; (2) sham group; (3) ischemia/reperfusion (I/R) group, in which the rat heart suffered from 60 min ischemia followed by 30 min reperfusion; (4) IP plus I/R group; (5) EET plus I/R group, in which 6.28×10^-8 mol/L 11, 12-EET was injected intravenously 20 min before I/R. The heart function was examined, and phosphorylated ERK and p38 MAPK were detected by Western blot. RESULTS: At 30 min reperfusion, +dp/dt_max, -dp/dt_max and LVDP decreased significantly in I/R group compared with sham group, IP plus I/R group and EET plus I/R group; Phosphorylated ERK1/2 level was higher in I/R group than sham group, but was lower in I/R group than IP plus I/R group and EET plus I/R group; Phosphorylated p38 MAPK level was lower in control, sham, IP plus I/R and EET plus I/R group than I/R group. CONCLUSION: 11,12-EET protects rat heart against ischemia/reperfusion injury, the mechanism may be related to activation of ERK1/2 and inhibition of p38 MAPK.     

Effect of ischemic preconditioning on vascular reactivity and calcium sensitivity in hemorrhagic shock rats

AIM: To investigate the effect of ischemic preconditioning (IPC) on vascular reactivity and calcium sensitivity during hemorrhagic shock. METHODS: Appropriate method of IPC was selected by observing the effect of different strategies of IPC on the survival time and the survival rate in hemorrhagic shock rats. The effect of IPC on the pressor effect of norepinephrine (NE, 3 μg/kg) and the contractile response of superior mesenteric artery (SMA) to NE and calcium in vivo and in vitro were observed. RESULTS: Among 3 strategies of IPC, 3 cycles of abdominal aorta occlusion for 1 min and loosing for 5 min increased the survival time and 24 h survival rate significantly, which was superior to the other two IPC methods. In vivo, IPC significantly increased the pressor response to NE and the contractile response of SMA to NE (P<0.01). In vitro, IPC significantly improved the reactivity of SMA to NE and Ca²⁺. The E_max values of SMA to NE and Ca²⁺ in IPC group were significantly higher than that in shock control group (P<0.01). CONCLUSION: Ischemic preconditioning reverses Shock-induced vascular hyporeactivity via improving calcium sensitivity of the vasculatures.