Effect of verapamil on conversion of xanthine dehydrogenase to oxidase in ischemic rat liver

The effect of organ flushing with the calcium entry blocker verapamil on the conversion of innocent enzyme xanthine dehydrogenase (XDH) to superoxide generating enzyme xanthine oxidase (XOD) in ischemic rat livers was studied. This enzyme conversion progressed over time in warm or cold ischemia. In non-flushed livers, the activities of XOD as percentages of XDH plus XOD after 6 h at 37°C and 6 days at 4°C were 80.3±5.2 and 31.6±2.1, respectively. In the livers flushed with Euro-Collins solution, the conversion was inhibited to 37.0±3.9% (P<0.001) after 6 h of warm ischemia, while this, inhibitory effect was not found in cold ischemia. Verapamil given through the portal vein on flushing further suppressed the conversion in both warm and cold ischemia (with 5.0 μM of verapamil, 21.2±5.8% (P<0.001) after 6 h of warm ischemia and 25.2±3.3% (P<0.01) after 6 days of cold ischemia). A similar effect was also obtained with the addition of 10 or 30 mM of EGTA instead of verapamil. In contrast, no inhibitory effect on conversion was obtained in livers flushed and homogenized with 10.0 μM of verapamil followed by incubation for 6 h at 37°C. In the livers that were flushed and stored at a warm temperature for 6h, verapamil reduced the increase of tissue lipid peroxidation product (P<0.02) after 15 min of reperfusion. Although the precise mechanisms of these inhibitory effects of verapamil on the enzyme conversion are still uncertain, it is though that organ flushing with verapamil might reduce the XOD-mediated postischemic reperfusion injury in livers subjected to prolonged ischemia.     

缺血预处理对离体大鼠肺缺血再灌注氧化损伤的影响

目的 :研究缺血预处理 (IP)对离体大鼠肺缺血再灌注氧化损伤的影响。方法 :建立离体大鼠肺缺血再灌注损伤模型。 18只SD大鼠随机分为 3组 ,每组 6只。对照组 (Con)持续平衡灌注通气 60min ,无缺血 ;缺血再灌注组 (IR)缺血 45min ,再灌注 3 0min ;缺血预处理组 (IP)先给予连续 2次的 5min缺血、5min再灌注的预处理 ,再行缺血 45min和再灌注 3 0min。测定缺血前和再灌注末灌注液中丙二醛 (MDA)、超氧化物歧化酶 (SOD)和白细胞数量 ,测定再灌注末肺组织髓过氧化物酶 (MPO)活性、黄嘌呤氧化酶 (XOD)活性和湿 /干比 (W /D)。结果 :IR组再灌末MDA含量、MPO活性、XOD活性和W /D较Con组明显升高 (P <0 0 1) ,而SOD活性则显著下降 (P <0 0 1)。IP能明显减少再灌后MDA、MPO、XOD和W /D的增加 ,提高SOD的活性 (P <0 0 1)。结论 :IP能明显抑制离体大鼠肺缺血再灌注导致的氧化损伤。     

Rapid conversion to high xanthine oxidase activity in viable Kupffer cells during hypoxia.

It has been widely postulated that the central mechanism of hepatic reperfusion injury involves the conversion, during ischemia, of the enzyme xanthine dehydrogenase (XDH) to its free radical-producing form, xanthine oxidase (XOD). However, this theory has been questioned because (a) XDH to XOD conversion in whole liver occurs very slowly; (b) the cellular distribution of XDH/XOD is unclear; and (c) the direct demonstration of XDH to XOD conversion in viable cells is lacking. In this paper, we address all three issues by measuring XDH to XOD conversion and cell viability in purified populations of hepatic endothelial cells (EC), Kupffer cells (KC), and hepatocytes (HEP). Although XDH/XOD activity on a cellular basis was greater in hepatocytes (0.92 +/- 0.12 mU/10(6) cells) than ECs (0.03 +/- 0.01) or KCs (0.12 +/- 0.04), XDH + XOD specific activity was similar in all three cell types (HEP 1.85 +/- 0.10 U/g protein; EC 1.69 +/- 0.54; KC 2.30 +/- 0.22). Over 150 min of warm (37 degrees C) or 24 h of cold (4 degrees C) hypoxia, percent XOD activity increased slowly in ECs, from 21 +/- 2% (basal) to 39 +/- 3% (warm) and 49 +/- 5% (cold) and in HEPs (29 +/- 2% to 38 +/- 3% and 49 +/- 2%), but converted significantly faster in KCs (28 +/- 3% to 91 +/- 7% and 94 +/- 4%). The dramatic changes in Kupffer cell XOD during cold hypoxia occurred despite only minor changes in cell viability. When hypoxic KCs were reoxygenated after 16 h of cold hypoxia, there was a marked increase in cell death that was significantly blocked by allopurinol. These data suggest that significant conversion to the free radical-producing state occurs within viable KCs, and that Kupffer cell XOD may play an important role in mediating reperfusion injury in the liver.     

Human xanthine dehydrogenase cDNA sequence and protein in an atypical case of type I xanthinuria in comparison with normal subjects

To investigate the properties of xanthine dehydrogenase/xanthine oxidase (XDH/XO) deficiency in a patient with atypical type I xanthinuria, as indicated by oxypurine data, a cDNA sequence encoding XDH, XDH/XO immunoblot analysis and a competitive PCR assay were performed, and the results were compared with those of normal subjects. The xanthine dehydrogenase cDNA sequence of the patient was consistent with the controls, while immunologically reactive 150 kD XDH/XO protein was not present in the xanthinuric duodenal mucosa, unlike the control duodenal mucosa. In addition, a decrease in XDH/XO messenger RNA was found by competitive PCR. These results suggest that atypical type I xanthinuria is due to a decrease in messenger RNA of XDH/XO. Furthermore, it was considered that this decrease could explain the normal plasma level and near normal urinary excretion of hypoxanthine seen in this case of xanthinuria, though XDH/XO activity and protein were not detected spectrophotometrically and immunologically, respectively.     

Enhanced activity of the free radical producing enzyme xanthine oxidase in hypoxic rat liver. Regulation and pathophysiologic significance.

It has been widely proposed that conversion of xanthine dehydrogenase (XDH) to its free radical-producing form, xanthine oxidase (XOD), underlies ischemic/reperfusion injury, although the relationship of this conversion to hypoxia and its physiologic control have not been defined. This study details the time course and control of this enzymatic interconversion. In a functionally intact, isolated perfused rat liver model, mean % XOD activity increased as a function of both the duration (25 to 45% in 3 h) and degree (r = 0.97) of hypoxia. This process was markedly accelerated in ischemic liver by an overnight fast (45 vs. 30% at 2 h), and by imposing a short period of in vivo ischemia (cardiopulmonary arrest 72%). Moreover, only under these conditions was there a significant rise in the XOD activity due to the conformationally altered XDH molecule (XODc, 18%), as well as concomitant morphologic injury. Neither circulating white blood cells nor thrombosis appeared to contribute to the effects of in vivo ischemia on enzyme conversion. Thus, it is apparent that conversion to the free radical-producing state, with high levels of XOD activity and concurrent cellular injury, can be achieved during a relatively short period of hypoxia under certain well-defined physiologic conditions, in a time course consistent with its purported role in modulating reperfusion injury. These data also suggest that the premorbid condition of organ donors (e.g., nutritional status and relative state of hypoxia) is important in achieving optimal organ preservation.     

Activities of xanthine oxidoreductase and antioxidant enzymes in different tissues of diabetic rats

Oxidative stress is an important pathogenic constituent in diabetic endothelial dysfunction. The aim of this study was to investigate whether an increase in oxidative stress related to xanthine oxidoreductase occurs in diabetes. Liver, brain, heart, and kidney xanthine oxidase (XO), xanthine dehydrogenase (XDH), antioxidant enzymes (glutathione peroxidase, superoxide dismutase, catalase), and nitrite levels were measured in control and early and late diabetic rat models. Although diabetes had no impact on liver XO and XDH activity, XDH activity in heart, kidney, and brain was significantly greater in late diabetic rats than in controls. Selenium glutathione peroxidase (GPx) activity was found to be lower in the liver, brain, kidney, and heart of late diabetic rats than in controls. The measured decrease in selenium GPx activity was also observed in early diabetic heart, kidney, and brain. No significant change was observed in liver, brain, and kidney copper/zinc superoxide dismutase (Cu/Zn SOD) activity in early and late diabetic rat models compared with that in controls, whereas heart Cu/Zn SOD activity was significantly decreased in both early and late diabetic rats. Liver and brain catalase activity remained similar among the different experimental groups, whereas increased heart and kidney catalase activity was observed in both early and late diabetic rats. Liver, kidney, and brain nitrite levels were found to be increased in early diabetic rat models compared with those in controls. These data suggest that the increased XDH and decreased selenium GPx activity observed in the later stages of diabetes leads to enhanced oxidative stress in the heart, kidney, and brain, resulting in secondary organ damage associated with the disease.     

Allopurinol enhanced adenine nucleotide repletion after myocardial ischemia in the isolated rat heart.

Allopurinol, a competitive inhibitor of xanthine oxidase, has been shown to have a protective effect on ischemic myocardium, but its mechanism of action remains controversial. We used an isolated rat heart preparation to test the hypothesis that allopurinol could restore adenosine triphosphate (ATP) levels and improve the recovery of left ventricular function after global myocardial ischemia. Hearts were equilibrated for 30 min, subjected to 10 min of global, normothermic (37 degrees C) ischemia, and reperfused for 15, 30, and 60 min. Hearts treated with allopurinol (100 microM) exhibited greater ATP levels and improved function during reperfusion than did untreated control hearts. Hearts treated with hypoxanthine (100 microM), the substrate for xanthine oxidase, also showed increased ATP and functional recovery compared with controls. These results suggest that allopurinol may protect the globally ischemic myocardium by enhancing the salvage of hypoxanthine for reincorporation into adenine nucleotides.     

Protective effect of allopurinol on hepatic energy metabolism in ischemic and reperfused rat liver

Reactive oxygen species generated by xanthine oxidase during reperfusion of ischemic liver might in part be responsible for ischemic organ injury. In normothermic ischemia/reperfusion rat model, we investigated whether allopurinol pretreatment improved ischemia-induced mitochondrial dysfunction. Rats were subjected to 60 min of hepatic ischemia and to 1 h and 5 h of reperfusion thereafter. At 18 h and 1 h before ischemia, the animals received 0.25 mL of either saline or allopurinol (50 mg/kg) i.p. In saline-treated ischemic rats, serum aspartate aminotransferase levels increased significantly at 5 h (4685 +/- 310 IU/L) and were significantly reduced with allopurinol pretreatment. Similarly, mitochondrial lipid peroxidation was elevated in the saline-treated ischemic group, but this elevation was prevented by allopurinol. In contrast, mitochondrial glutamate dehydrogenase activity and ketone body ratio decreased in the saline-treated group, but this decrease was also inhibited by allopurinol. Hepatic ATP levels in the saline-treated rats were 42% lower 5 h after reperfusion. However, treatment with allopurinol resulted in significantly higher ATP levels. Allopurinol treatment preserved the concentration of AMP in ischemic liver but inhibited the accumulation of xanthine in reperfused liver. Our findings suggest allopurinol protects against mitochondrial injury, which prevents a mitochondrial oxidant stress and lipid peroxidation and preserves the hepatic energy metabolism.     

丹参对大鼠肝脏缺血再灌注损伤的抗氧化作用

目的探讨丹参对大鼠缺血再灌注损伤肝脏的抗氧化作用。方法建立大鼠全肝缺血再灌注模型,60只大鼠随机分为三组,每组20只,分别为对照组(A组)、肝缺血/再灌注组(B组)和肝缺血/再灌注加丹参治疗组(C组),分别在肝缺血前、缺血45min、再灌注45min共3个时相点,检测血浆超氧化物歧化酶(SOD)活性、黄嘌呤氧化酶(XO)活性、丙二醛(MDA)浓度以及血清谷丙转氨酶(ALT)活性。结果肝缺血/再灌注组,血浆XO、MDA及ALT显著高于对照组、SOD明显低于对照组(P<0.05和<0.01)。而丹参治疗组与缺血/再灌注组比较,上述指标均有显著性差异(P<0.05和<0.01)。结论丹参可通过降低氧自由基水平(增强SOD活性、减弱XO活性),拮抗脂质过氧化反应(降低MDA浓度),从而减轻肝脏缺血再灌注损伤。     

Oxygen free radicals in ischemic acute renal failure in the rat.

During renal ischemia, ATP is degraded to hypoxanthine. When xanthine oxidase converts hypoxanthine to xanthine in the presence of molecular oxygen, superoxide radical (O-2) is generated. We studied the role of O-2 and its reduction product OH X in mediating renal injury after ischemia. Male Sprague-Dawley rats underwent right nephrectomy followed by 60 min of occlusion of the left renal artery. The O-2 scavenger superoxide dismutase (SOD) was given 8 min before clamping and before release of the renal artery clamp. Control rats received 5% dextrose instead. Plasma creatinine was lower in SOD treated rats: 1.5, 1.0, and 0.8 mg/dl vs. 2.5, 2.5, and 2.1 mg/dl at 24, 48, and 72 h postischemia. 24 h after ischemia inulin clearance was higher in SOD treated rats than in controls (399 vs. 185 microliter/min). Renal blood flow, measured after ischemia plus 15 min of reflow, was also greater in SOD treated than in control rats. Furthermore, tubular injury, judged histologically in perfusion fixed specimens, was less in SOD treated rats. Rats given SOD inactivated by prior incubation with diethyldithiocarbamate had plasma creatinine values no different from those of control rats. The OH X scavenger dimethylthiourea (DMTU) was given before renal artery occlusion. DMTU treated rats had lower plasma creatinine than did controls: 1.7, 1.7, and 1.3 mg/dl vs. 3.2, 2.2, and 2.4 mg/dl at 24, 48, and 72 h postischemia. Neither SOD nor DMTU caused an increase in renal blood flow, urine flow rate, or solute excretion in normal rats. The xanthine oxidase inhibitor allopurinol was given before ischemia to prevent the generation of oxygen free radicals. Plasma creatinine was lower in allopurinol treated rats: 2.7, 2.2, and 1.4 mg/dl vs. 3.6, 3.5, and 2.3 mg/dl at 24, 48, and 72 h postischemia. Catalase treatment did not protect against renal ischemia, perhaps because its large size limits glomerular filtration and access to the tubular lumen. Superoxide-mediated lipid peroxidation was studied after renal ischemia. 60 min of ischemia did not increase the renal content of the lipid peroxide malondialdehyde, whereas ischemia plus 15 min reflow resulted in a large increase in kidney lipid peroxides. Treatment with SOD before renal ischemia prevented the reflow-induced increase in lipid peroxidation in renal cortical mitochondria but not in crude cortical homogenates. In summary, the oxygen free radical scavengers SOD and DMTU, and allopurinol, which inhibits free radical generation, protected renal function after ischemia. Reperfusion after ischemia resulted in lipid peroxidation; SOD decreased lipid peroxidation in cortical mitochondria after renal ischemia and reflow. We concluded that restoration of oxygen supply to ischemic kidney results in the production of oxygen free radicals, which causes renal injury by lipid peroxidation.     

The effect of desferal on rat heart mitochondrial function, iron content, and xanthine dehydrogenase/oxidase conversion during ischemia-reperfusion

Cardiac mitochondrial function as measured by oxidative phosphorylation is impaired by ischemia; and, this deteriorates even further on reperfusion of the heart. Free oxygen radicals, especially the formation of hydroxyl radicals via the iron-catalyzed Haber-Weiss and Fenton reactions have been implicated in the reperfusion injury. In this study, the effect of desferrioxamine (desferal) in the perfusate on mitochondrial function of isolated rat hearts during different periods of normothermic ischemic cardiac arrest (NICA), and subsequent reperfusion was investigated. Mitochondrial functions measured were the QO2 (state 3); ADP/O ratio and oxidative phosphorylation; the mitochondrial, loosely bound (chelateable) iron (LB-iron); the xanthine dehydrogenase and xanthine oxidase activities. Inclusion of desferal in the perfusion solution significantly improved mitochondrial function during the different NICA periods, and prevented the deterioration of mitochondrial function resulting from reperfusion. Desferal did not significantly affect the LB-iron content of the mitochondria or the ratio of xanthine dehydrogenase/xanthine oxidase activities in the mitochondria during NICA or reperfusion. Our experiments suggest that iron, which is free to be chelated by desferal, plays a role in this injury to the rat myocardium.     

Xanthine oxidase-derived hydrogen peroxide contributes to ischemia reperfusion-induced edema in gerbil brains.

The contribution of toxic O2 metabolites to cerebral ischemia reperfusion injury has not been determined. We found that gerbils subjected to temporary unilateral carotid artery occlusion (ischemia) consistently developed neurologic deficits during ischemia with severities that correlated with increasing degrees of brain edema and brain H2O2 levels after reperfusion. In contrast, gerbils treated just before reperfusion (after ischemia) with dimethylthiourea (DMTU), but not urea, had decreased brain edema and brain H2O2 levels. In addition, gerbils fed a tungsten-rich diet for 4, 5, or 6 wk developed progressive decreases in brain xanthine oxidase (XO) and brain XO + xanthine dehydrogenase (XD) activities, brain edema, and brain H2O2 levels after temporary unilateral carotid artery occlusion and reperfusion. In contrast to tungsten-treated gerbils, allopurinol-treated gerbils did not have statistically significant decreases in brain XO or XO + XD levels, and reduced brain edema and brain H2O2 levels occurred only in gerbils developing mild but not severe neurologic deficits during ischemia. Finally, gerbils treated with DMTU or tungsten all survived, while greater than 60% of gerbils treated with urea, allopurinol, or saline died by 48 h after temporary unilateral carotid artery occlusion and reperfusion. Our findings indicate that H2O2 from XO contributes to reperfusion-induced edema in brains subjected to temporary ischemia.     

Effect of verapamil on conversion of xanthine dehydrogenase to oxidase in ischemic rat liver

The effect of organ flushing with the calcium entry blocker verapamil on the conversion of innocent enzyme xanthine dehydrogenase (XDH) to superoxide generating enzyme xanthine oxidase (XOD) in ischemic rat livers was studied. This enzyme conversion progressed over time in warm or cold ischemia. In non-flushed livers, the activities of XOD as percentages of XDH plus XOD after 6 h at 37 degrees C and 6 days at 4 degrees C were 80.3 +/- 5.2 and 31.6 +/- 2.1, respectively. In the livers flushed with Euro-Collins solution, the conversion was inhibited to 37.0 +/- 3.9% (P less than 0.001) after 6 h of warm ischemia, while this inhibitory effect was not found in cold ischemia. Verapamil given through the portal vein on flushing further suppressed the conversion in both warm and cold ischemia (with 5.0 microM of verapamil, 21.2 +/- 5.8% (P less than 0.001) after 6 h of warm ischemia and 25.2 +/- 3.3% (P less than 0.01) after 6 days of cold ischemia). A similar effect was also obtained with the addition of 10 or 30 mM of EGTA instead of verapamil. In contrast, no inhibitory effect on conversion was obtained in livers flushed and homogenized with 10.0 microM of verapamil followed by incubation for 6 h at 37 degrees C. In the livers that were flushed and stored at a warm temperature for 6 h, verapamil reduced the increase of tissue lipid peroxidation product (P less than 0.02) after 15 min of reperfusion. Although the precise mechanisms of these inhibitory effects of verapamil on the enzyme conversion are still uncertain, it is thought that organ flushing with verapamil might reduce the XOD-mediated postischemic reperfusion injury in livers subjected to prolonged ischemia.     

异丙酚对围术期缺血-再灌注损伤肝脏的保护作用

目的　探讨异丙酚对围术期肝脏缺血再灌注损伤 (HIRI)的防治作用及其机制。方法　选择 18例肝癌手术患者 ,观察肝门阻断前后及再灌注后血中超氧化物歧化酶 (SOD)活性、黄嘌呤氧化酶 (XO)活性、脂质过氧化物 (L PO)浓度和丙氨酸转氨酶 (AL T)值 ;对再灌注 2 5 min时的肝组织进行电镜下肝细胞形态学变化的观察 ,以评价异丙酚对上述指标的影响。结果　 HIRI期间 ,SOD活性显著下降 (P<0 .0 1) ,XO活性、L PO浓度及 AL T值明显升高 (P均 <0 .0 1) ;肝组织超微结构发生异常改变。使用异丙酚后 ,上述指标的异常变化显著减轻 ,其差异有显著意义 (P<0 .0 5或 P<0 .0 1)。结论　异丙酚可通过降低氧自由基水平、拮抗脂质过氧化反应 ,对围术期 HIRI起积极的防治作用。     

别嘌呤醇对家兔低血容量性休克-再灌注损伤的防治作用

目的探讨别嘌呤醇对家兔血容量性休克—再灌注损伤的保护作用。方法制备家兔低血容量性休克模型,随机分为非保护组（n＝10）和别嘌呤醇保护组（n＝10）,并检测血浆和心、肺等组织黄嘌呤氧化酶（XO）活性、丙二醛（MDA）含量及平均动脉压（MAP）值。结果休克前两组动物XO、MDA及AIAP均无统计学差异。休克90分钟时两组动物MAP均显著下降,XO及MDA均明显升高。休克—再灌注后,保护组XO及MDA均逐渐下降,休克—再灌注3小时后接近休克前水平,明显低于休克90分钟时和非保护组同时相水平;保护组MAf,逐渐上升,休克—再灌注3小时后接近休克前水平,明显高于休克90分钟时及非保护组同时相水平。此外,别瞟吟醇保护组心、肺、肝、肾、肠道组织XO及MDA均明显低于非保护组XO及MDA值。结论别嘌呤醇通过抑制黄瞟吟氧化酶活性、减少氧自由基生成可减轻组织休克—再灌注损伤。     

The effectiveness of postischemic oxypurinol administration upon myocardial function in the isolated rat heart

The Langendorff isolated rat heart preparation was used to determine the effect of oxypurinol, a xanthine oxidase inhibitor, on myocardial function when administered during reperfusion after 30 min of warm ischemia. Twenty rats were randomly sorted into 2 groups of 10, and an isolated heart preparation made from each rat. The isolated hearts were perfused for 15 min with a modified Krebs-Henseleit solution to permit stabilization of the preparation. Each heart was then subjected to 30 min of total ischemia at 37 degrees C followed by 40 min of reperfusion with either saline-treated perfusate or oxypurinol-treated perfusate (1.3 mM). The maximum power produced and the preload required to produce maximum power were both determined prior to ischemia and every 10 min after ischemia during 40 min of reperfusion. The saline-treated group, but not the oxypurinol-treated group, showed significantly less maximum power output at all testing times during reperfusion compared to the preischemic value (P less than 0.05). There was a significantly greater maximum power output (P less than 0.02) in the oxypurinol-treated group compared to the saline-treated group after 20, 30, and 40 min of reperfusion. There were no differences within either group, or between groups, for the preload required to produce maximum power at any of the testing times. Ultrastructural examination of myocardium after reperfusion showed severe mitochondrial and myofibrillar disruption in the saline-treated group but not in the oxypurinol-treated group. We conclude that oxypurinol administered following 30 min of total ischemia at the onset of reperfusion, can preserve myocardial function during the early reperfusion period in the isolated rat heart.     

血液稀释和缺血预处理对猪心脏缺血再灌注损伤的保护作用

目的在猪心肌缺血再灌注模型上,观察等容血液稀释和缺血预处理对再灌注损伤心肌的保护作用. 方法 18头小型猪建立急性心肌缺血模型,随机分为 3组对照组 (组Ⅰ, n=6),缺血预处理组 (组Ⅱ, n=6),缺血预处理加血液稀释组 (组Ⅲ, n=6),测定心排血量( CO) ,混合静脉血氧饱和度( SvO2,) 、冠状动脉血流量,计算心肌氧供,氧耗量.于钳扎前、解除钳扎后 20,60 min分别测定血浆中丙二醛 (MDA),SOD活性、磷酸激酶( CPK)及肌酸磷酸激酶同功酶( CK-MB) ,自左心耳剪下标本,测定 HSP 70 mRNA表达率. 结果①缺缺血 20 min 时 3组 MAP、 CI及 SVRI明显减低( P< 0.01) ,但 I组下降幅度明显大于 II,III组.再灌注 60 min时, II组 ,III组 HR明显低于对照值( P< 0.01) ,III组 HR的变化则无统计学意义, I组 MAP,CI的下降幅度明显大 I组和 II组 (P< 0.05).②再灌注 20 min及 60 min时, III组的冠脉血流量明显大于 I组( P< 0.05).③再灌注 20 min和 60 min时, 3组 CPK, CPK-MB均较对照值明显升高( P< 0.05- 0.01) ,组 I的升高幅度明显大于组 II, 组 III.组Ⅰ SOD值在再灌注 20 min, 60 min时逐步降低( P< 0.05),组 II, 组 III SOD值有升高趋势,与对照值比较,无统计学意义.再灌注 60 min时,组Ⅰ MDA值明显高于组Ⅱ,组Ⅲ.④组Ⅰ HSP 70 mRNA表达低于组Ⅱ和组Ⅲ. 结论等容血液稀释可明显增强预适应拮抗心肌缺血再灌注造成的心肌损伤.     

脑缺血再灌注引起大鼠脑细胞水肿及脑组织超氧化物歧化酶活性的变化

背景脑缺血再灌注产生的自由基主要是黄嘌呤氧化酶,导致梗死灶容积细胞肿胀.目的观察脑缺血再灌注引起脑自由基清除酶超氧化物歧化酶活性的变化,探讨嘌呤氧化酶抑制剂别嘌呤醇对缺血再灌注脑组织细胞含水量的影响.设计完全随机对照实验.单位沈阳医学院附属中心医院神经内科,中国医科大学附属第一医院神经外科,辽宁省肢体伤残矫形医院.材料实验于2003-05/2004-04在沈阳医学院附属中心医院实验室完成.选择Wistar大鼠40只,随机分为4组,每组10只.缺血+别嘌呤醇组脑缺血6 h,灌胃给予100mg/kg别嘌呤醇;缺血+悬浊剂组脑缺血6 h,灌胃给予相同剂量的悬浊剂(恶喹酸溶液);缺血再灌注+别嘌呤醇组脑缺血6 h,再灌注2 h,灌胃给予100 mg/kg别嘌呤醇;缺血再灌注+悬浊剂组脑缺血6 h,再灌注2 h,灌胃给予相同剂量的悬浊剂.其中别嘌呤醇组于脑缺血前48 h,24h和1 h共3次分别以100 mg/kg剂量灌胃给予别嘌呤醇.悬浊剂组同样方法给予悬浊剂.方法缺血+别嘌呤醇组、缺血+悬浊剂组的大鼠于闭塞后6 h,缺血再灌注+别嘌呤醇组、缺血再灌注+悬浊剂组于灌注后2 h测量脑组织含水量.脑组织过氧化物歧化酶分布采用过氧化物歧化酶免疫染色观察.主要观察指标①脑组织过氧化物歧化酶分布.②各组大鼠脑组织含水量.结果40只大鼠全部进入结果分析.①脑组织过氧化物歧化酶分布缺血+悬浊剂组、缺血再灌注+悬浊剂组铜锌超氧化物歧化酶染色,缺血灶内可见全部明显的染色增强.缺血+悬浊剂组的锰过氧化物歧化酶染色、缺血灶内可见血管周围轮状染色增强.同时可见染色增强的血管壁和神经细胞.缺血再灌注+悬浊剂组缺血灶内染色呈现弥漫性、稍低下.缺血+别嘌呤醇组和缺血再灌注+别嘌呤醇组铜锌过氧化物歧化酶都没有变化、在缺血+别嘌呤醇组可见血管周围染色增强,缺血再灌注+别嘌呤醇组未见弥漫性改变.缺血+悬浊剂组、缺血再灌注+悬浊剂组小动脉内皮细胞核肿大、中层肌细胞膨大、血管膜扩大,脑组织血管周围显著呈海绵状.缺血+别嘌呤醇组、缺血再灌注+别嘌呤醇组这些变化减轻.②各组大鼠脑组织含水量缺血+别嘌呤醇组,缺血再灌注+别嘌呤醇组低于缺血+悬浊剂组和缺血再灌注+悬浊剂组[(78.56±0.30)%,(79.08±0.33)%;(78.85±0.49)%,(79.86±0.49)%,(P＜0.05)].结论别嘌呤醇可通过对过氧化物歧化酶的抑制有效减轻脑缺血再灌注后的组织损伤.     

The effect of hypoxia, reoxygenation, ischemia, and reperfusion on hydraulic permeability in rat mesenteric venules

Little is known regarding the effects of I/R on hydraulic permeability (Lp). We sought to compare the individual influences of hypoxia, ischemia, reoxygenation, and reperfusion on Lp. We hypothesized that (1) hypoxia increases Lp; (2) reoxygenation further increases Lp; (3) ischemia results in greater increases in Lp compared with hypoxia; (4) reperfusion causes additional increases in Lp compared with hypoxia, ischemia, and reoxygenation; and (5) xanthine oxidase (XO) and white blood cell adherence play important roles in hypoxia, ischemia, and reperfusion. Hydraulic permeability was measured by an in vivo microcannulation technique during hypoxia, reoxygenation, ischemia, and reperfusion in rat mesenteric postcapillary venules. Additional rats were fed a Tungsten-enriched diet to inhibit XO activity, and the studies were repeated. White blood cell adherence was also documented. Hypoxia and ischemia both increased Lp 2-fold from baseline levels (P < 0.001). Reoxygenation did not alter Lp compared with 15 min of hypoxia alone (P > 0.07). Reperfusion after hypoxia increased Lp 6-fold (P < 0.001). Reperfusion after ischemia also increased Lp 6-fold (P < 0.001). Inhibition of XO had no effect on the increase in Lp after both hypoxia and ischemia. However, inhibition of XO attenuated the 6-fold increase in Lp observed during reperfusion after both hypoxia and ischemia by approximately 50% (P < 0.001). White blood cell adherence increased during reperfusion but not hypoxia or ischemia. The complexity of I/R injury makes it a difficult clinical scenario to model for research. We have demonstrated in an in vivo model that hypoxia and ischemia increase Lp similarly, and that reperfusion has a profound deleterious effect on Lp. These changes in Lp seem to be XO and white blood cell dependent.