Reduction of myocardial ischemic injury with oxygen-derived free radical scavengers

Experimental data suggesting that oxygen-derived free radicals may play a role in the myocardial injury associated with ischemia and reperfusion are presented. In several studies of prolonged global myocardial ischemia, the administration of free radical scavenging agents, such as superoxide dismutase, catalase, and mannitol, resulted in significantly better recovery of left ventricular function following reperfusion. In a region-at-risk model of localized myocardial ischemia, both superoxide dismutase and allopurinol significantly reduced the extent of myocardial necrosis that developed following reversible coronary arterial branch occlusion. The manner in which oxygen-derived free radicals may be harmful is examined. In particular, the possibility that these toxic species are involved in the exacerbation of the ischemic injury that develops upon reflow and reoxygenation is examined.     

The role of oxygen-derived free radicals and the effect of free radical scavengers on skeletal muscle ischemia/reperfusion injury

The aim of this study was to clarify the role of oxygen-derived free radicals and the effect of free radical scavengers on skeletal muscle ischemia/reperfusion injury. Male Wistar rats were divided into a complete ischemia group (C-group) and an incomplete ischemia group (IC-group) and each animal was subjected to 2h of ischemia and 1h of reperfusion. In an attempt to decrease reperfusion injury, the rats were given free radical scavengers either as allopurinol 50 mg/kg for 2 days or as superoxide dismutase 60,000 units/kg plus catalase 500,000 units/kg. Tissue malondialdehyde, a product of lipid peroxidation, was measured as an indicator of free radicals, with higher levels indicating higher concentrations of free radicals. The malondialdehyde level in the gastrocnemius muscle after 1h of reperfusion increased significantly in both groups when compared to the levels before and 2h after ischemia, although there was no significant difference between the two groups. The water content of the gastrocnemius muscle and serum creatinine phosphokinase MM isoenzyme (CPK-MM) in both groups, and GOT in the C-group, increased significantly after 1h of reperfusion when compared the values before and 2h after ischemia. In the C-group, these values were significantly higher than in the IC-group. The administration of free radical scavengers suppressed the increase in malondialdehyde in the gastrocnemius muscle after reperfusion in both groups. The increase in water content and CPK-MM after reperfusion was also suppressed by free radical scavengers in the IC-group, but not in the C-group. These findings suggest that ischemic damage predominates in complete severe ischemia/reperfusion injury, whereas reperfusion injury predominates in incomplete mild ischemia/reperfusion injury.     

Oxygen-derived free radical scavengers and skeletal muscle ischemic/reperfusion injury

Total injury in ischemic skeletal muscle is a function of ischemic damage and reperfusion injury. In an attempt to decrease reperfusion injury, we gave the oxygen-derived free radical scavengers allopurinol, superoxide dismutase, or mannitol during reperfusion of canine gracilis muscle made ischemic for 4 hours. We measured muscle O2 consumption (MVO2), and tissue calcium, water, and adenosine triphosphatase (ATP) before ischemia, after ischemia, and at 5 minutes and 60 minutes of reperfusion. The results at 60 minutes showed no improvement in MVO2 or ATP. In fact, ATP was significantly depressed with allopurinol and superoxide dismutase treatment, and tissue edema did not decrease in any of the groups. We conclude that the simple addition of oxygen-derived free radical scavengers during the initial reperfusion of totally ischemic skeletal muscle does not attenuate reperfusion injury.     

Influence of oxygen-derived free radical scavengers on ischemic livers

It has been hypothesized that the formation of oxygen-derived free radicals may play an important part in ischemically induced tissue injury. Using a canine ischemic liver model, we have assessed the role of two oxygen-free radical scavengers, catalase (CAT) and superoxide dismutase (SOD), used alone and in combination, on the recovery of ischemic livers. Liver ischemia was induced in adult mongrel dogs by cross-clamping of the portal vein and hepatic artery for 40 min. Hepatectomy was then performed, and livers were tested in an isolated perfusion model with 500 ml of an albumin-mannitol solution at 37 degrees C for 3 hr. Liver function tests were performed hourly during the perfusion period. Biopsies and 99m-Tc-HIDA scans were also done at the end of perfusion. Livers in group 1 (n = 6) served as controls and were not pretreated prior to ischemic injury. Livers in group 2 (n = 6), group 3 (n = 6), and group 4 (n = 6) were pretreated, respectively, with CAT (5000 U/kg), SOD (5000 U/kg), and SOD and CAT in combination (5000 U/kg) each. The results indicated that the oxygen-derived free radical scavengers, CAT and SOD, were able to provide partial protection against the free radicals accumulated during ischemic damage. These studies offer some potential avenues for the protection of livers prior to and after transplantation.     

Shock-reinfusion injury to the central organs and the effect of free radical scavengers in the rat

Hemorrhagic shock-reinfusion injury produces critical changes in various organs with the generation of oxidant-free radicals. Some papers have reported that shock-reinfusion injury to the intestine is effectively reduced by the scavengers of free radicals; however, few reports mention the central organ damage caused by systemic hemorrhagic shock-reinfusion injury. Using a rat systemic hemorrhagic shock model, injury to the central organs, being the brain, heart, lungs, liver, and kidneys was assessed by measuring malondialdehyde (MDA). The MDA levels in the lungs, kidneys, and liver were elevated significantly after reinfusion, although there was no elevation of MDA in the brain or heart. These data show that the lungs, liver, and kidneys are easily damaged by shock-reinfusion, but that the brain and heart are relatively resistant. The efficacy of the free radical scavengers, superoxide dismutase plus catalase and allopurinol, were evaluated 30 min after reinfusion. Pathological examination showed that superoxide dismutase plus catalase and allopurinol reduced reinfusion injury in the lungs, liver, and kidneys. Moreover, superoxide dismutase plus catalase reduced MDA levels in both the liver and kidneys, whereas allopurinol reduced MDA levels only in the kidneys after reinfusion. However, these free radical scavengers could not suppress the elevation of MDA in the lungs after reinfusion.     

Acute lung injury following reperfusion after ischemia in the hind limbs of rats.

In this study, we proposed that oxygen free radicals participate in the acute pulmonary injury that follows limb ischemia/reperfusion. Using an established model of hind limb ischemia, reproducible lung injury occurred after reperfusion. Lung microvascular permeability was measured with 125I-BSA and increased two-fold after 30 minutes of reperfusion. Pulmonary injury was blocked with DMSO, DMTU, allopurinol, indomethacin, and SOD plus catalase. The degree of pulmonary neutrophil sequestration as assessed by tissue myeloperoxidase activity was significantly diminished in animals pretreated with antioxidants. Pretreatment with indomethacin did not attenuate the neutrophil sequestration within the pulmonary parenchyma. These data suggest that increased lung microvascular permeability and neutrophil accumulation occur following hind limb ischemia/reperfusion. Therapeutic interventions with oxygen radical inhibitors blocked this process, while the prostaglandin inhibitor, indomethacin, only reduced lung permeability.     

A prostacyclin analogue reduces free radical generation in heart-lung transplantation.

The mechanism by which prostacyclin acts to prevent in vivo reperfusion injury is still uncertain. This study was therefore undertaken to assess the effect of a stable prostacyclin analogue (OP 41483-alpha-CD [OP]) on oxygen-derived free radicals after heart-lung transplantation. OP was administered to the heart-lung graft through the pulmonary artery for 25 minutes encompassing the reperfusion process. Free radicals were directly measured by electron spin resonance spectroscopy. The radical intensities of pulmonary venous blood were significantly lower in the OP group than in the control group, suggesting that fewer free radicals were generated in the lungs of the OP group. The cardiac and respiratory function were better in the OP group than in the control group. The lung is the primary source of oxygen free radical attack, and the beneficial action of OP on free radical generation is almost exclusively restricted to the lung and does not apply to the heart. This result suggested that OP probably is effective in inhibiting free radical generation from the endothelium.     

Improved survival in free skin flap transfers in rats

We have demonstrated previously that oxygen-derived free radicals are important mediators of tissue injury in experimental island skin flaps that have been subjected to prolonged ischemia (vascular occlusion) followed by reperfusion. In this study the role of oxygen free radicals in ischemia/reperfusion injury has been investigated in free flap transfers. Groin skin flaps were harvested, stored at room temperature for 21 to 24 hours, and transplanted to the contralateral groin. These free flap transfers normally exhibit a high incidence of complete necrosis. Treatment before the onset of reperfusion with a single dose of superoxide dismutase (SOD), a scavenger of superoxide radicals, increased the survival rate of these skin flaps from 38% in the control group to 76% (p less than 0.025). Tissue levels of SOD were measured before ischemia, after ischemia but before reperfusion, and 30 minutes after reperfusion: untreated flap tissues, which were destined to undergo necrosis, exhibited a significant decrease in SOD activity after reperfusion, whereas SOD-treated flap tissues, destined to survive, demonstrated increased enzyme activity. High levels of tissue SOD activity thus appeared to be associated with improved flap survival. The results have significant clinical implications with regard to organ preservation and transplantation.     

Prevention of edema formation in the perfused lung preparation by oxygen radical scavengers

Oxygen-derived free radicals have been implicated as mediators of pulmonary microvascular injury. In the present study we addressed the question of the role of radicals formed in the lung parenchyma in development of pulmonary edema. Rat lungs were perfused with cell-free solutions with and without addition of colloid. Edema formation was measured as dry-wet weight ratios. Edema developed following 30 min perfusion with all perfusates except nonoxygenated Dextran-Tyrode. Addition of free radical scavengers, superoxide dismutase and catalase, reduced the edema formation with the various oxygenated perfusates. We conclude that in the isolated lung perfused with oxygenated solutions oxygen-derived radicals are formed that mediate increased permeability.     

Oxygen-derived free radical damage in canine heart transplantation

To study the role of free radical-induced myocardial injury during heart transplantation, five groups of dog hearts were orthotopically transplanted. Control group I and experimental groups II, III, and IV (each n = 8) were reperfused for 1 hr after 49 min of operational ischemia. Control group V (n = 4) remained ischemic for 90 min. In the three experimental groups, the free radical scavengers superoxide dismutase (10 mg/kg; group II), catalase (10 mg/kg; group III), or both (10 mg/kg each; group IV) were administered just before reperfusion and during reperfusion for 1 hr. The generation of free radicals, remained at low levels in all groups during ischemia, but significantly increased when groups I-IV were reperfused. This increase was also associated with an increase in creatinine kinase MB isoenzyme. In the experimental groups, free radical scavengers significantly inhibited the appearance of thiobarbituric acid reactive substances and the release of creatinine kinase MB isoenzyme during reperfusion (P less than 0.05). Regarding cardiac functions, 60 min after the termination of the cardiopulmonary bypass, a significant improvement was demonstrated in the treated groups (P less than 0.05). These results indicate that (1) the generation of oxygen free radicals occurs primarily during reperfusion, (2) both superoxide dismutase and catalase reduce production of free radicals during this time, and (3) combined administration did not provide a greater improvement in cardiac metabolic recovery. This study confirms the efficacy of free radical scavengers during heart transplantation.     

Measurement of free radical generation from endothelial cells and observation of cell injury exposed to anoxia-reoxygenation]

Oxygen free radicals have been demonstrated to be important mediators in postischemic reperfusion injury. In this study, I determined the superoxide and the hydrogen peroxide generation from human umbilical endothelial cells on reoxygenation following anoxic incubation (1% O2, 5% CO2, 94% N2). The superoxide generation, detected by the reduction of cytochrome, c, was at its maximum 3 minutes after reoxygenation in any anoxic interval. The hydrogen peroxide production, detected by the fluorometric analysis, was observed later than that of superoxide. Treatment of EC with superoxide dismutase and allopurinol attenuated the superoxide production, and catalase attenuated the hydrogen peroxide. Cell injury was assessed by both fura-2 release assay and trypan blue dye exclusion methods. Although cell injury was less than 20% in anoxic condition, it was remarkably increased after reoxygenation. However this cell injury was not completely prevented in the presence of free radical scavengers. Allopurinol was more effective than superoxide dismutase or catalase. In conclusion, EC are the major source of free radicals in postischemic reperfusion which are originated mainly from xanthine-xanthine oxidase system and these radicals may also contribute, at least in part, to the EC injury.     

Prevention of free radical-induced myocardial reperfusion injury with allopurinol

Growing evidence supports the concept that oxygen free radicals are an important cause of myocardial ischemic and reperfusion injury. This study was designed to determine if toxic oxygen metabolites may exacerbate ischemic injury upon reoxygenation. Left ventricular function was studied in a group of seven dogs receiving intermittent, 4 degrees C, hyperosmolar, hyperkalemic (KCI 25 mEq/L) saline cardioplegic solution. This group was compared to a group (n = 7) receiving a hyperkalemic (KCI 25 mEq/L) cardioplegic solution designed to scavenge superoxide anion and hydroxyl radical: superoxide dismutase (3,000 U/ml) and mannitol (325 mOsm/L). A third group of five animals received allopurinol pretreatment (50 mg/kg/day) for 72 hours and hyperkalemic saline cardioplegic solution. After 60 minutes of ischemia (10 degrees to 15 degrees C) and 45 minutes of reperfusion, left ventricular mechanical function was better in the groups receiving free radical scavengers and allopurinol pretreatment than in the group receiving only hyperkalemic saline cardioplegic solution. Free radical scavengers preserved myocardial function in this model of hypothermic global ischemia and reperfusion. Our data support the concept that injury occurs primarily during reperfusion with the generation of oxygen free radicals via the hypoxanthine-xanthine oxidase reaction. Allopurinol has potential clinical application in the prevention of reperfusion injury.     

Xanthine oxidase: its role in the no-reflow phenomenon.

This study was designed to probe the hypothesis that oxygen-derived free radicals are involved in initiation of the no-reflow phenomenon. We developed a reproducible model of no reflow in the rat hind limb. Laser Doppler studies confirmed that the hind limbs perfused well after 2 or 4 hours of ischemia, but perfusion ceased in the first 10 minutes after 6 hours of ischemia. Venous blood samples and biopsy specimens of skin and muscle were taken after 2 and 4 hours of ischemia to study tissue injury. Blood samples were evaluated for xanthine oxidase (XO), xanthine dehydrogenase, and creatine phosphokinase (CPK) activities. Conjugated dienes and iodine 125-labeled albumin extravasation were quantified in tissue samples. Groups of animals were treated with inhibitors of XO (allopurinol), antioxidant enzymes (superoxide dismutase plus catalase), and free radical scavengers (dimethyl sulfoxide and dimethyl thiourea) to assess the roles of free radicals in ischemia-reperfusion injury in the hind limbs. After 4 hours of ischemia followed by reperfusion, plasma XO activity rose threefold over preischemia levels (p less than 0.05). Xanthine dehydrogenase activity did not change; conjugated diene levels in muscle rose twofold; CPK levels rose sixfold, and 125I albumin extravasation rose twofold (p less than 0.05). Pretreatment with the XO inhibitor allopurinol reduced XO activity to negligible levels and significantly attenuated conjugated diene levels, CPK levels, and albumin extravasation. Albumin extravasation was also significantly attenuated by pretreating animals with superoxide dismutase together with catalase, dimethyl thiourea, and dimethyl sulfoxide. In all animals pretreated with allopurinol or superoxide dismutase and catalase, reperfusion persisted after 6 hours of ischemia. These data suggest that, in ischemia followed by reperfusion, tissue injury is related to oxygen products derived from XO activity.     

The primary localization of free radical generation after anoxia/reoxygenation in isolated endothelial cells

While free radical-mediated reperfusion injury is clearly important in a variety of disparate organs, the particular cellular source of these radicals is unclear. To address this question, we subjected relatively pure (92% +/- 3% by factor VIII immunoassay) cultures of rat pulmonary artery endothelial cells to 0 to 45 minutes of anoxia (95% N2, 5% CO2), followed by reoxygenation (95% air, 5% CO2), to simulate ischemia/reperfusion. Cell injury was assayed after reoxygenation by the release of previously incorporated 51chromium and/or lactate dehydrogenase, and viability was determined by means of trypan blue exclusion. These three end points correlated closely. Without anoxia, the cells remained viable, with minimal evidence of injury for the entire experimental period, while 45 minutes of hypoxia followed by 30 minutes of reoxygenation produced substantial evidence of cell injury in 71% +/- 6% of the cells. This injury was reduced to 21% +/- 2% by treatment with the highly specific free radical scavengers superoxide dismutase and catalase together, either before anoxia or after anoxia, but just before reoxygenation. Similar protection was provided by xanthine oxidase inhibition with allopurinol. The injury was mimicked (without anoxia) by the exogenous generation of superoxide radicals with xanthine and xanthine oxidase. These experiments establish the essential components of free radical generation at reperfusion to be localized within the isolated endothelial cell in the absence of neutrophils or parenchymal cells.     

The role of oxygen free radicals in mediating the reperfusion injury of cold-preserved ischemic kidneys

We evaluated the hypothesis that postischemic renal failure is caused primarily at reperfusion by oxygen-derived free radicals in a swine model designed to realistically mimick human cadaveric renal transplantation. Both kidneys were removed, flushed with Euro-Collins solution, stored 24 hr at 4 degrees C, and then transplanted to a second pig. Experiments were paired, each pig receiving one treated and one control kidney. All pigs received the optimal conventional regimen of hydration, phenoxybenzamine, furosemide, and mannitol to allow assessment of free radical treatment superimposed thereupon. Two days later creatinine clearance (CCR) was measured from each kidney via separate ureterostomies. Untreated kidneys developed severe functional impairment, CCR falling from a normal level of 25.5 +/- 6.3 ml/min (n = 8) to 7.7 +/- 0.9 ml/min (n = 14, P less than .05 vs. control). The infusion of 20 mg of the free radical scavenger superoxide dismutase (SOD) into the renal artery at reperfusion substantially ameliorated this injury (CCR = 15.9 +/- 1.7 ml/min, n = 18, P less than 0.05 vs. control). A dose-response curve to SOD showed no effect of doses of 0.2 mg (CCR = 8.0 +/- 1.1 ml/min, n = 4) or 2 mg (CCR = 7.7 +/- 0.9, n = 5), and no greater benefit from 100 mg (CCR = 16.1 +/- 2.1 ml/min, n = 3, P less than 0.05 vs. control). Blocking the generation of superoxide radicals from xanthine oxidase with allopurinol (50 mg/kg) afforded similar protection (CCR = 18.2 +/- 1.8; n = 11, P less than 0.01 vs. control). On the other hand, following an 18-hr period of cold ischemia, little damage was sustained by the untreated (control) kidneys (CCR = 22.1 +/- 0.6 ml/min). Consequently, under these conditions the ablation of free radical generation with allopurinol provided no significant benefit. These findings suggest that after a critical period of cold ischemic preservation, metabolic changes take place within the kidney that lead to free radical generation and consequent tissue injury upon reperfusion, despite optimal preservation by conventional methods. This damage can be prevented by simple nontoxic measures--which, therefore, show great promise for use in the prevention of early renal failure following cadaveric renal transplantation.     

Ablation of free radical-mediated reperfusion injury for the salvage of kidneys taken from non-heartbeating donors. A quantitative evaluation of the proportion of injury caused by reperfusion following periods of warm, cold, and combined warm and cold ischemia

Postischemic renal failure is a severe problem following cadaveric renal transplantation, especially if the kidney has been harvested from a non-heartbeating donor, and thereby subjected to periods of both warm and cold ischemia. It is well established that a substantial component of postischemic injury is produced by oxygen-derived free radicals generated from xanthine oxidase at reperfusion. However, the clinical potential of free radical ablative therapy is dependent upon the proportion of the total injury caused by this reperfusion mechanism, compared with the proportion resulting from ischemic injury per se. Therefore, we quantitatively evaluated these proportions in porcine kidneys subjected to various periods of warm (renal artery occlusion in situ), cold (harvest, cold preservation, and allotransplantation), and combined warm and cold ischemia. Experiments were paired, one kidney treated with either superoxide dismutase (SOD) or allopurinol for free radical ablation, the contralateral kidney serving as a control. Creatinine clearance (Ccr) was measured separately for each kidney 48 hr after reperfusion. After 1 and 2 hr of warm ischemia, Ccr dropped to 50% and 36% of normal, respectively. This was improved to 110% and 55% when SOD was given into the renal artery at reperfusion. Similarly, after 24 and 48 hr of cold ischemia, kidney function was significantly improved from 30% and 18% to 72% and 47% of normal, respectively, when allopurinol was added to the preservation solution. SOD used at harvest and again at reperfusion was particularly effective following combined warm and cold ischemia, in a situation mimicking the harvest of cadaver kidneys from a non-heartbeating donor. These findings suggest that the ablation of free radical-mediated reperfusion injury may improve posttransplant renal function sufficiently to allow expansion of the cadaveric donor pool to include non-heartbeating donors.     

肢体缺血预处理对兔肺组织缺血再灌注后氧自由基及细胞因子分泌的影响

目的 研究肢体缺血预处理对兔肺组织缺血再灌注后氧自由基及细胞因子分泌的影响.方法 将18只日本大耳白兔随机分为对照组(C组)、缺血再灌注组(I/R组)及肢体缺血预处理组(L组),每组6只.实验结束时,取肺组织测定湿/干重比(W/D)、超氧化物歧化酶(SOD)和髓过氧化物酶(MPO)活性、丙二醛(MDA)和肿瘤坏死因子(TNF)-α、白介素(IL)-6、IL-8及IL-10的含量;检测支气管肺泡灌洗液和血清中蛋白含量,计算肺通透性指数;观察肺组织病理学变化.结果 与I/R组比较,L组W/D、肺通透性指数、MPO活性、MDA和TNF-α、IL-6、IL-8的含量均降低(P<0.05),SOD活性(P<0.05)和IL-10含量升高(P<0.01).C、L两组间上述指标的差异无统计学意义(P>0.05).光镜榆查结果发现L组肺组织病理学改变较I/R组明显减轻.结论 肢体缺血预处理可以抑制缺血再灌注肺组织中氧自由基产生和促炎细胞因子TNF-α、IL-6、IL-8的释放,上调抗炎细胞因子IL-10的合成,从而减轻肺缺血再灌注损伤.     

Protection against oxygen-induced reperfusion injury of the isolated canine heart by superoxide dismutase and catalase

While oxygen-derived free radicals have been implicated in the pathogenesis of myocardial injury, the exact nature of this injury is still unclear. To test the hypothesis that oxygen-induced injury may influence the recovery of cardiac function from ischemic damage, we used an oxygen free radical scavenger, superoxide dismutase (SOD), together with catalase, during the reperfusion of isolated canine heart which had been subjected to 15 min of normothermic ischemic arrest followed by 2 hr of hypothermic cardioplegic preservation using a modified Collins solution. Determinations of thiobarbituric acid reactive substances and coenzyme Q10 within the myocardium showed that the treatment with SOD and catalase was capable of inhibiting lipid peroxidation induced by reperfusion. This inhibition was apparently associated with the improvement of myocardial energy metabolism and cardiac performance. Coronary flow was significantly higher in the heart treated with SOD and catalase during the working stage with a corresponding increase in oxygen consumption. Myocardial adenosine triphosphate (ATP) was partially, but significantly restored during reperfusion in these hearts whereas no restoration was observed in the heart without the enzymes. The treatment with SOD and catalase also improved left ventricular stroke work index and left ventricular maximum dp/dt at an early stage of the working mode. These results suggest that the use of SOD and catalase during reperfusion can protect the ischemic heart against reperfusion injury by scavenging oxygen-derived free radicals.     

Hypoxia and reoxygenation of the lung tissues induced mRNA expressions of superoxide dismutase and catalase and interventions from different antioxidants

OBJECTIVE: Hypoxic pulmonary vasoconstriction (HPV) is a well-known phenomenon to temporarily offset a ventilation/perfusion mismatch. Sustained HPV may lead to pulmonary hypertension. In this protocol, we studied the relationships between the HPV response and oxygen radical release after hypoxia/reoxygenation (H/R) challenge in an isolated perfused lung model. MATERIALS AND METHODS: We used an in situ isolated rat lung preparation. Two hypoxic challenges (5% CO(2)-95% N(2)) were administered for 10 minutes each with administration of antioxidants of superoxide dismutase (SOD; 2 mg/kg), catalase (20,000 IU/kg), dimethylthiourea (DMTU; 100 mg/kg), dimethylsulfoxide (DMSO; 1 mL/kg), or allopurinol (30 mg/kg) between 2 challenges. We measured pulmonary arterial pressure changes before, during, and after H/R challenge. We measured blood concentration changes in hydroxyl radicals and nitric oxide (NO) before and after H/R. mRNA expressions of SOD and catalase in lung tissue were measured after the experiments. RESULTS: Hypoxia induced pulmonary vasoconstriction by increasing pulmonary arterial pressure and consecutive hypoxic challenges did not show tachyphylaxis. Blood concentrations of hydroxyl radicals and NO increased significantly after H/R challenges. mRNA expressions of SOD and catalase increased significantly, however, neither SOD nor catalase showed attenuated effects on HPV responses. Small molecules of DMTU, DMSO, and allopurinol attenuated the HPV responses. CONCLUSIONS: H/R induced increases in the expressions of SOD and catalase in lung tissues. DMTU, DMSO, and allopurinol antioxidants attenuated the HPV responses by reducing the oxygen radical release.     

Inhibition of the compartment syndrome by the ablation of free radical-mediated reperfusion injury

Skeletal muscle edema secondary to an increase in capillary permeability after reflow is an important cause of the compartment syndrome after acute arterial revascularization. The purpose of this study was to investigate the possible role of oxygen free radicals, generated at reperfusion, in the pathogenesis of the compartment syndrome secondary to acute arterial ischemia/reperfusion. A reproducible model of this syndrome was produced in anesthetized rabbits by femoral artery occlusion after surgical devascularization of collateral branches from the aorta to the popliteal artery. Increasing periods of ischemia from 6 to 12 hours, followed by 2 hours of reperfusion, were associated with corresponding increases in the anterior muscle compartment hydrostatic pressure and inversely proportional decreases in tibialis anterior muscle blood flow within that compartment as assessed by xenon 133 washout (n = 46) (r = -0.62, p less than 0.001). Anterior compartment pressure increased from 5 +/- 1 to 48 +/- 5 mm Hg (n = 46) (p less than 0.001) after 7 hours of total arterial ischemia and 2 hours of reperfusion. Ablation of free radicals generated from xanthine oxidase with either allopurinol (n = 8) or oxypurinol (n = 8), by scavenging the superoxide radical at reperfusion with superoxide dismutase (n = 8), or by blocking secondary hydroxyl radical formation with deferoxamine (n = 8) significantly ameliorated the rise in compartment pressure (p less than 0.05) in each case; it also significantly improved muscle perfusion in the superoxide dismutase-, allopurinol-, and deferoxamine-treated animals (p less than 0.05). These findings indicate that development of the compartment syndrome after acute arterial revascularization may be due, at least in part, to microvascular injury mediated by oxygen-derived free radicals generated from xanthine oxidase at reperfusion.