Superoxide dismutase (SOD) activity in hypoxic mammalian systems

Protective effect of curculigo orchioides extract on cyclophosphamide-induced neurotoxicity in murine model

Free radicals are one of the frequent products of normal cellular metabolism. Disparity of metabolism and excessive generation of free radicals predisposes to disorders like Parkinson's disease, Alzheimer's disease, and aging phenomenon. Curculigo orchioides Gaertn. is known for “adaptogen” and “aphrodisiac” activity and has been proved for antiasthmatic, estrogenic, antiosteoporotic activity along with protection from cisplatin-induced cell damage. C. orchioides was powdered and subjected to soxhlet extraction using methanol. Phytochemical studies and estimation of polyphenols and flavonoids was performed. Acute toxicity studies were performed by Organization for Economic Cooperation and Development OECD guidelines. Animals were treated with cyclophosphamide to induce neurotoxicity. Curculigo orchioides was powdered and subjected to soxhlet extraction using methanol. Catalase, superoxide dismutase, glutathione peroxidase, and lipid peroxidation were estimated by reported methods. C. orchioides (400 mg/kg) significantly promoted restoration of catalase (P < 0.005), superoxide dismutase (P < 0.005), and glutathion (P < 0.05) levels. Similarly, a very significant decrease (P < 0.005) in the levels of malondialdehyde was observed. In all cases as mentioned previously, C. orchioides at dose 200 mg/kg promoted significant (P < 0.05) restoration of enzyme levels. C. orchioides (Kali Musli) is rich source of phytochemicals like flavonoids and polyphenols. Flavonoids and polyphenols are reputed to demonstrate neuroprotective effect. These phytochemicals in the present study might be responsible to demonstrate neuroprotective effect.

Efficacy of aqueous extract of Hippophae rhamnoides and its bio-active flavonoids against hypoxia-induced cell death

Objectives:

To investigate the protective efficacy of aqueous extract of Hippophae rhamnoides against chronic hypoxic injury using primary rat hepatocytes.

Materials and Methods:

The extract was prepared using maceration method and characterized by its phenolic and flavonoid content and chemical antioxidant capacity using ferric reducing antioxidant power assay. Hepatocytes were maintained in hypoxia chamber (3% and 1% oxygen) for 72 h. The cells kept under normoxic condition served as control. The cells were treated with the extract and flavonoids; isorhamentin, kaempferol or qurecetin-3-galactoside. After the end of exposure period; cell survival, reactive oxygen species (ROS), leakage of lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), reduced glutathione (GSH), glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels were measured.

Results:

The extract showed presence of high phenolic and flavonoid content with significant antioxidant activity in chemical assay. The cell exposed to hypoxia showed concentration dependent cell death and harbored higher reactive oxygen species. In addition, these cells showed significant leakage of intracellular LDH, ALT, and AST accompanied by the diminished levels/activities of GSH, GPx, and SOD. The treatment of cells with aqueous extract of H. rhamnoides reduced hypoxia-induced cell death and prevented increase in ROS levels and leakage of intracellular LDH, ALT, and AST from cells. Moreover, these cells maintained better levels/activities of GSH, GPx, and SOD in comparison to the respective controls. The major flavonoids present in aqueous extract of H. rhamnoides; quercetin-3-galactoside, kaempferol, and isorhamentin also prevented hypoxia induced cell injury individually or in combination, however, the protection offered by these compounds taken together could not match to that of the extract.

Conclusions:

Overall the findings reveal significance of aqueous extract of H. rhamnoides in controlling ROS-meditated hypoxic injury in cells and can be useful in many hepatic complications.

Recombinant PTD-Cu/Zn SOD attenuates hypoxia-reoxygenation injury in cardiomyocytes

BACKGROUND

Oxidative stress plays a pivotal role in myocardial ischemia-reperfusion injury. Increasing the protein expression of intracellular Cu/Zn SOD, which is the major endogenous antioxidant enzyme, may attenuate or prevent hypoxia-reoxygenation injury (HRI) in cultured cardiomyocytes. However, ectogenic Cu/Zn-SOD can hardly be transferred into cells to exert biological effects. In this study, we constructed PTD-Cu/Zn SOD plasmid with a kind of translocation structure-Protein transduction domain (PTD) and detected its transmembrane ability and antioxidant effects in H9c2 rat cardiomyocytes subjected to hypoxia/reoxygenation injury (HRI).

METHODS

We constructed the pET-PTD-Cu/Zn SOD (CDs) prokaryotic expression vectors in plasmid that were inserted into E. coli BL21 to induce the protein expression of PTD-Cu/Zn SOD. H9c2 cardiomyocyte HRI was achieved by exposing cardiomyocytes to 12 h hypoxia followed by 2 h reoxygenation. Protein expression of PTD-Cu/Zn SOD in cardiomyocytes was assayed by Western blot and their enzyme activities were investigated by immunohistochemistry and flow cytometry.

RESULTS

In cultured cardiomyocytes hypoxia-reoxygenation injury model, exogenous PTD-Cu/Zn SOD could penetrate cell membrane to clear superoxide anion and decrease hydrogen peroxide level in H9c2 cardiomyocytes subjected to HRI. The level of mitochondrial membrane potential was restored to normal, and the cell apoptosis was reduced in cardiomyocytes with PTD-Cu/Zn SOD treatment during HRI.

CONCLUSION

Recombinant PTD-Cu/Zn SOD could scavenge intracellular-free superoxide anion, protect mitochondria from damages, and attenuate the hypoxia-reoxygenation injury in cultured cardiomyocytes.

Effects of tiletamine-zolazepam anaesthesia on plasma antioxidative status and some haematological parameters in sheep

It is not clear whether the anaesthetic agents tiletamine and zolazepam have antioxidant or pro-oxidant effects. Therefore, this study was carried out to investigate the effects of tiletamine-zolazepam anaesthesia on oxidant/antioxidant status in blood plasma and on haematological parameters in 10 healthy Awassi ewes. The tiletamine-zolazepam combination was administrated in a dose of 7.5 mg/kg intramuscularly. The animals were spontaneously breathing air during the procedure. Blood samples were collected by jugular venipuncture before induction and at 30, 60, 120 min, 24 h and 3 days after anaesthesia. Malondialdehyde concentration, an index of lipid peroxidation, was higher at 30, 60, 120 min and 24 h (P < 0.05) than the baseline value in the plasma. The level of glutathione decreased (P < 0.05) at 30, 60 and 120 min, then returned to the baseline level. Beta-carotene concentration was lower (P < 0.05) than the baseline value during anaesthesia with the exception of its level at 120 min. Glutathione peroxidase and catalase activities decreased (P < 0.05) at the onset of anaesthesia, then returned to baseline values. There was no significant change in vitamin A level. Red blood cell count, haematocrit and haemoglobin concentration significantly decreased (P < 0.05) only at 30 min and thereafter they gradually returned to the baseline values. Based on the results tiletamine-zolazepam anaesthesia seems to accelerate lipid peroxidation and to impair the enzymatic antioxidant defence in the blood plasma.

Lung ischemia-reperfusion injury: implications of oxidative stress and platelet-arteriolar wall interactions

Pulmonary ischemia-reperfusion (IR) injury may result from trauma, atherosclerosis, pulmonary embolism, pulmonary thrombosis and surgical procedures such as cardiopulmonary bypass and lung transplantation. IR injury induces oxidative stress characterized by formation of reactive oxygen (ROS) and reactive nitrogen species (RNS). Nitric oxide (NO) overproduction via inducible nitric oxide synthase (iNOS) is an important component in the pathogenesis of IR. Reaction of NO with ROS forms RNS as secondary reactive products, which cause platelet activation and upregulation of adhesion molecules. This mechanism of injury is particularly important during pulmonary IR with increased iNOS activity in the presence of oxidative stress. Platelet-endothelial interactions may play an important role in causing pulmonary arteriolar vasoconstriction and post-ischemic alveolar hypoperfusion. This review discusses the relationship between ROS, RNS, P-selectin, and platelet-arteriolar wall interactions and proposes a hypothesis for their role in microvascular responses during pulmonary IR.

Effects of hypoxia and hypoxic training on 8-hydroxydeoxyguanosine and glutathione levels in the liver

The effects of hypoxia and hypoxic training on 8-hydroxydeoxyguanosine (8-OHdG), reduced glutathione (GSH), and oxidized glutathione (GSSG) levels and on glutathione reductase (GR) activity in the liver of rats were evaluated. Rats were divided into 3 groups: a hypoxia and exercise (HE) group, a hypoxia and sedentary (HS) group, and a normoxia and sedentary (NS) group. The liver 8-OHdG levels were lower in the HE and HS groups compared with the NS group (P <.05). No significant difference between in the liver 8-OHdG levels in the HE and HS groups were found. However, the liver GSH level in the HS group was lower than that in the NS group (P <.05), and the HE group had significantly higher levels of liver GSH than the HS group (P <.01). The activity of liver GR in the HS group was lower than that of the NS group (P <.05). Moreover, the liver GR activity of the HE group was significantly higher than that of the HS group (P <.01). No significant difference in liver GR activity between the HE and NS groups was noted. In conclusion, the present study confirmed that moderate hypoxia and hypoxic training attenuated liver DNA damage and decreased liver GSH levels and GR activity. These results indicate that moderate hypoxia and hypoxic training result in decreased oxidative stress.

Superoxide dismutases in the lung and human lung diseases

The lungs are directly exposed to higher oxygen concentrations than most other tissues. Increased oxidative stress is a significant part of the pathogenesis of obstructive lung diseases such as asthma and chronic obstructive pulmonary disease, parenchymal lung diseases (e.g., idiopathic pulmonary fibrosis and lung granulomatous diseases), and lung malignancies. Lung tissue is protected against these oxidants by a variety of antioxidant mechanisms among which the superoxide dismutases (SODs) are the only ones converting superoxide radicals to hydrogen peroxide. There are three SODs: cytosolic copper-zinc, mitochondrial manganese, and extracellular SODs. These enzymes have specific distributions and functions. Their importance in protecting lung tissue has been confirmed in transgenic and knockout animal studies. Relatively few studies have been conducted on these enzymes in the normal human lung or in human lung diseases. Most human studies suggest that there is induction of manganese SOD and, possibly, extracellular SOD during inflammatory, but not fibrotic, phases of parenchymal lung diseases and that both copper-zinc SOD and manganese SOD may be downregulated in asthmatic airways. Many previous antioxidant therapies have been disappointing, but newly characterized SOD mimetics are being shown to protect against oxidant-related lung disorders in animal models.

Adaptative response of antioxidant enzymes in different areas of rat brain after repeated d-amphetamine administration

d-Amphetamine has been shown to be a potential brain neurotoxic agent, particularly to dopaminergic neurones. Reactive oxygen species indirectly generated by this drug have been indicated as an important factor in the appearance of neuronal damage but little is known about the adaptations of brain antioxidant systems to its chronic administration. In this study, the activities of several antioxidant enzymes in different areas of rat brain were measured after repeated administration of d-amphetamine sulphate (sc, 20 mg/kg/day, for 14 days), namely glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GRed), catalase, and superoxide dismutase (SOD). When compared to a pair-fed control group, d-amphetamine treatment enhanced the activity of GST in hypothalamus to 167%, GPx in striatum to 127%, in nucleus accumbens to 192%, and in medial prefrontal cortex to 139%, GRed in hypothalamus to 139%, as well as catalase in medial prefrontal cortex to 153%. However, the same comparison revealed a decrease in the activity of GRed in medial pre-frontal cortex by 35%. Food restriction itself reduced GRed activity by 49% and enhanced catalase activity to 271% in nucleus accumbens. The modifications observed for the measured antioxidant enzymes reveal that oxidative stress probably plays a role in the deleterious effects of this drug in CNS and that, in general, the brain areas studied underwent adaptations which provided protection against the continuous administration of the drug.

Operation Everest III (Comex'97): the effect of simulated sever hypobaric hypoxia on lipid peroxidation and antioxidant defence systems in human blood at rest and after maximal exercise

Eight subjects were placed in a decompression chamber for 31 days at pressures from sea level (SL) to 8848 m altitude equivalent. Whole blood lipid peroxidation (LP) was increased at 6000 m by a mean of 23% (P<0.05), at 8000 m by 79% (P<0.01) and at 8848 m by 94% (P<0.01). (All figures are means.) Two days after return to sea level (RSL), it remained high, by 81% (P<0.01), while corresponding erythrocyte GSH/GSSG ratios decreased by 31, 46, 49, 48%, respectively (each P<0.01). Erythrocyte SOD and plasma ascorbate did not change significantly. At sea level, maximal exercise induced a 49% increase in LP (P<0.01), and a 27% decrease in erythrocyte GSH/GSSG ratio relative to resting values (P<0.05). At 6000 m, the LP was enhanced further from 23 (P<0.05) to 66% (P<0.01), and after RSL from 81 (P<0.01) to 232% (P<0.01), while pre-exercise GSH/GSSG ratios did not change significantly. Exercise did not change plasma ascorbate relative to sea level or to 6000 m, but decreased after RSL by 32% (P<0.01). These findings suggest that oxidative stress is induced by prolonged hypobaric hypoxia, and is maintained by rapid return to sea level, similar to the post-hypoxic re-oxygenation process. It is increased by physical exercise.

Skeletal muscle dysfunction in chronic obstructive pulmonary disease and chronic heart failure: underlying mechanisms and therapy perspectives

Low exercise tolerance has a large influence on health status in chronic obstructive pulmonary disease and chronic heart failure. In addition to primary organ dysfunction, impaired skeletal muscle performance is a strong predictor of low exercise capacity. There are striking similarities between both disorders with respect to the muscular alterations underlying the impairment. However, different alterations occur in different muscle types. Histologic and metabolic data show that peripheral muscles undergo a shift from oxidative to glycolytic energy metabolism, whereas the opposite is observed in the diaphragm. These findings are in line with the notion that peripheral and diaphragm muscle are limited mainly by endurance and strength capacity, respectively. In both diseases, muscular impairment is multifactorially determined; hypoxia, oxidative stress, disuse, medication, nutritional depletion, and systemic inflammation may contribute to the observed muscle abnormalities and each factor has its own potential for innovative treatment approaches.

Changes in the defense against free radicals in the liver and plasma of the dog during hypoxia and/or halothane anaesthesia

Defenses against free radicals were evaluated in the dog under different conditions of ventilation. Changes in the levels of reduced glutathione (GSH), alpha-tocopherol (vitamin E), ascorbic acid (vitamin C) and the lipid peroxidation end-products, estimated as malondialdehyde (MDA) and the activity of superoxide dismutase (SOD), were studied in serial liver biopsies from dogs ventilated with either oxygen, halothane and oxygen, hypoxic gas mixture of 8% oxygen and 92% nitrogen or halothane under hypoxic conditions. Simultaneous determination of GSH, vitamin E and MDA were carried out in the plasma. The results showed time-dependent depletion of GSH and vitamin E in liver and plasma and vitamin C in the liver. This was accompanied by a simultaneous increase in the levels of MDA. The magnitude of the change was in the following order: halothane and hypoxia > hypoxia > halothane and oxygen > oxygen. The greatest depletion was observed for vitamin E and the least for vitamin C. The rise in the level of MDA in plasma was much higher than in the liver tissue. Hypoxia resulted in inhibition of liver SOD activity. It seems that increased production of free radicals under hypoxic conditions may have overwhelmed the anti-oxidant defenses in the liver. In addition, the much higher level of MDA in plasma, as compared to liver tissue, may indicate that MDA could have originated in tissues or organs other than the liver and leaked into the blood, indicating possible damage in other locations in the body.

Ischemic and reperfusion injury of cyanotic myocardium in chronic hypoxic rat model: changes in cyanotic myocardial antioxidant system

OBJECTIVE

The objective was to evaluate the effect of left ventricular function on cyanotic myocardium after ischemia-reperfusion and to determine the effect of cyanosis on the myocardial antioxidant system.

METHODS

Cyanotic hearts (cyanotic group) were obtained from rats housed in a hypoxic chamber (10% oxygen) for 2 weeks and control hearts (control group) from rats maintained in ambient air. Isolated, crystalloid perfused working hearts were subjected to 15 minutes of global normothermic ischemia and 20 minutes of reperfusion, and functional recovery was evaluated in the two groups. Myocardial superoxide dismutase, glutathione peroxidase, glutathione reductase activity, and reduced glutathione content were measured separately in the cytoplasm and mitochondria at the end of the preischemic, ischemic, and reperfusion periods.

RESULTS

Mean cardiac output/left ventricular weight was not significantly different between the two groups. Percent recovery of cardiac output was significantly lower in the cyanotic group than in the control group (56.1% +/- 5.7% vs 73.0% +/- 3.1%, p = 0.001). Mitochondrial superoxide dismutase, mitochondrial and cytosolic glutathione reductase activity, and cytosolic reduced glutathione were significantly lower in the cyanotic group than in the control group at end-ischemia (superoxide dismutase, 3.7 +/- 1.3 vs 5.9 +/- 1.5 units/mg protein, p = 0.012; mitochondrial glutathione reductase, 43.7 +/- 14.0 vs 71.0 +/- 30.3 munits/mg protein, p = 0.039; cytosolic glutathione reductase, 13.7 +/- 2.0 vs 23.2 +/- 4.2 munits/mg protein, p < 0.001; and reduced glutathione, 0.69 +/- 0.10 vs 0.91 +/- 0.24 microgram/mg protein, p = 0.037).

CONCLUSIONS

Cyanosis impairs postischemic functional recovery and depresses myocardial antioxidant reserve during ischemia. Reduced antioxidant reserve at end-ischemia may result in impaired postischemic functional recovery of cyanotic myocardium.

Effects of hypobaric hypoxia on antioxidant enzymes in rats

1. The present study was undertaken to investigate the effects of hypobaric hypoxia, equivalent to an altitude of 5500 m, on antioxidant enzymes in rats. 2. Malondialdehyde levels in serum, heart, lung, liver and kidney of hypobaric-hypoxic rats were all significantly higher than in control rats by day 21 of exposure (P < 0.05), indicating increased oxidative stress. 3. Superoxide dismutase (SOD) catalyses the conversion of the superoxide anion to H2O2 and O2. The concentration of immunoreactive Mn-SOD in the serum of hypobaric-hypoxic rats was raised significantly from day 5 onwards, whereas in liver and lung, it had decreased significantly by day 21 (P < 0.05). 4. Glutathione peroxidase (GSH-Px) catalyses H2O2 and certain lipid peroxides. By day 21, GSH-Px activity had increased significantly in the heart and lungs, but decreased significantly in the liver (P < 0.05). 5. Catalase catalyses H2O2. Catalase activity in the liver and kidney of hypobaric-hypoxic rats was significantly decreased on day 1 (P < 0.05) though levels then recovered. 6. Mn-SOD mRNA in the liver of hypobaric-hypoxic rats was induced during the experiment, the effect being exceptionally marked, especially during the first 3 days of exposure to hypobaric hypoxia. 7. These results suggest that the liver may be more vulnerable than the other organs tested to oxidative stress under hypobaric hypoxia.

Oxidative stress induced by intermittent exposure at a simulated altitude of 4000 m decreases mitochondrial superoxide dismutase content in soleus muscle of rats

The effects were examined of 6-month intermittent hypobaric (4000 m) exposure on the antioxidant enzyme systems in soleus and tibialis muscles of rats. At the end of the 6-month experimental exposure, the six rats in both the exposed group and the control group were sacrificed. Immunoreactive mitochondrial superoxide dismutase (Mn-SOD) contents were measured as well as the activities of antioxidant enzymes [Mn-SOD, cytosolic SOD (Cu,Zn-SOD), catalase (CAT), and glutathione peroxidase (GPX)]. Thiobarbituric acid-reactive substances (TBARS) were also determined as an indicator of lipid peroxidation. The high altitude exposure resulted in a marked increase in TBARS content in soleus muscle, suggesting increased levels of oxygen free radicals. Conversely, significant decreases in both Mn-SOD content and activity in soleus muscle were noted after exposure. Such trends were not noticed in tibialis muscle. On the other hand, no significant changes in Cu,Zn-SOD, CAT, or GPX were observed in either muscle. These results suggested that the increases in lipid peroxidation were most probably a result of decreased Mn-SOD function which was more depressed in oxidative than in glycolytic muscle.

MnSOD protein content changes in hypoxic/hypoperfused lung tissue

Previous studies using an in vivo rabbit model in which lung tissue hypoxia/hypoperfusion was created by unilateral lung collapse for 7 days demonstrated a decrease in MnSOD activity in previously hypoxic/hypoperfused lungs. In the present study, we determined whether tissue hypoxia/hypoperfusion decreased MnSOD protein concentration or mRNA expression in the lung as well, changes that would suggest pretranslational regulation of enzyme activity. Expression of MnSOD may be critical in determining the degree of tissue injury during re-oxygenation because the mitochondrial electron transport system produces reactive oxygen species (ROS) both during hypoxia and re-oxygenation. We purified MnSOD protein from rabbit livers to a specific activity of approximately 3,500 U/mg protein and found the amino terminal sequence nearly identical to those of the rat and human MnSOD proteins. Lung MnSOD protein content was quantitated by immunoassay, and MnSOD mRNA content was determined by slot blotting. Results from five control and six experimental rabbits, the right lungs of which had been hypoxic/hypoperfused because of collapse for 7 days, demonstrated a 32% decrease (P < 0.03) in MnSOD protein content (42 +/- 8 micrograms/mg DNA in hypoxic lungs compared with 61 +/- 3 micrograms/mg DNA in contralateral lungs) that was not due to decreased numbers of mitochondria. Lung succinate dehydrogenase activity, a mitochondrial marker, did not change in hypoxic/hypoperfused lungs. The mRNA for MnSOD did not change relative to B-actin mRNA in lungs that had been hypoxic and hypoperfused for 7 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Human erythrocyte superoxide dismutase in adults, neonates, and normal, hypoxaemic, anaemic, and chromosomally abnormal fetuses

An enzyme-linked immunosorbent method is described for the assay of human erythrocyte superoxide dismutase (SOD). The method was specific and precise as well as simple, economical, and reliable. The mean levels of adult SOD with SD were 652 +/- 122 mg/kg hemoglobin (Hb) for males and 635 +/- 100 mg/kg Hb for females. In neonates the levels were 528 +/- 92 mg/kg Hb. Normal fetal levels at 20-36 weeks gestation were 421 +/- 90 mg/kg Hb. Mean SOD levels in hypoxemic growth-retarded fetuses and in anemic fetuses from red cell iso-immunised pregnancies (before their first intrauterine blood transfusion) were the same as those in normal fetuses. However, in a case of trisomy 21 the fetal level of SOD was significantly increased.

Arterial wall oxygenation, oxyradicals, and atherosclerosis

The oxygen supply of inner media and thickened intima of atherosclerosis prone arteries depends largely on diffusion from the endothelium. Conditions which increase wall thickness and oxygen diffusion or reduce oxygen transmissibility produce hypoxia and steep PO2 gradients within the wall. Cerebral injury and myocardial reperfusion studies indicate that intermittent hypoxia and steep PO2 gradients lead to oxyradical formation and tissue damage. Products of lipid and sterol peroxidation are found in atherosclerotic plaques and can be generated by arterial wall cells in culture. It is likely that peroxidation occurs directly within the arterial wall. Sufficient oxyradical generation occurs during normal oxygen metabolism that local scavenger mechanisms are required to avoid tissue damage. Experimental hypertension, hyperlipemia and balloon injury produce medial hypoxia with steep PO2 gradients and redistribution of the pattern of arterial wall antioxidant enzymes. This suggests that minor deviations from normal arterial wall anatomy and function can lead to oxyradicals which can be directly injurious and can amplify the atherogenic potential of lipoprotein infiltration.

Hepatic cytochrome P-450 in rats submitted to chronic hypobaric hypoxia

Hepatic cytochrome P-450 content in adaptation to hypobaric hypoxia was studied in three groups of rats and in their respective controls at sea level atmospheric pressure. The experimental groups were as follows: 1) young male and female rats submitted to 4,400 m (simulated altitude) for 6-8 mo, 2) the same animal model of group 1 submitted to 5,500 m (simulated altitude) for a subsequent period of 2-3 mo, and 3) adult males exposed to 5,500 m for 35 days. Hypoxia caused a marked polycythemia in all three groups, body weight loss in males of the three groups and at 5,500 m also in females, whereas liver weight was normal in groups 1 and 2 and slightly decreased in group 3. Cytochrome P-450 content measured in microsomal suspensions of groups 1 and 2 was unchanged. In liver homogenates, cytochrome P-450 content was normal at 4,400 m (group 1) and decreased at 5,500 m (groups 2 and 3). Therefore, endoplasmic reticulum mass, calculated as the ratio of cytochrome P-450 in the homogenates and in the isolated microsomes, was unchanged in group 1 (4,400 m) and decreased in group 2 (5,500 m). The content of antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase, measured in liver homogenates of group 3, were markedly decreased (by 40, 30, and 35%, respectively). Results do not support the hypothesis that an increase in cytochrome P-450 content plays a role in adaptation to hypoxia.

Lipid peroxidation during myocardial ischaemia induced by pacing

Oxygen derived free radical generation can be shown in experimental models of myocardial ischaemia and reperfusion and may cause cellular damage by peroxidizing polyunsaturated membrane phospholipids. An attempt was made to quantify human intracardiac lipid peroxidation during transient myocardial ischaemia by measuring the aortic and coronary sinus concentrations of malondialdehyde (a marker of lipid peroxidation) before, during, and after incremental pacing. Twenty six patients were paced until they had severe chest pain or 2 mm ST segment depression or they reached a paced rate of 180 beats/min. They were divided into two groups according to whether or not lactate was produced during pacing. Twelve patients (group 1), all with coronary artery disease, produced myocardial lactate during pacing. None of the other 14 patients (group 2), half of whom had coronary disease, produced lactate during pacing. Concentrations of malondialdehyde in the aorta and coronary sinus were significantly higher in group 1 than in group 2. Five minutes after the end of pacing coronary sinus malondialdehyde concentrations in group 1 had increased significantly from baseline values. There were no changes with time in the coronary sinus concentration of malondialdehyde in group 2 or in the aorta in either group. The negative malondialdehyde extraction ratio in group 1 suggests that intracardiac lipid peroxidation occurs during transient human myocardial ischaemia.

Re-expansion pulmonary edema. A potential role for free radicals in its pathogenesis

Re-expansion pulmonary edema (RPE) has been attributed to decreased lung interstitial pressures from a variety of mechanisms. Because some recent studies have implicated mechanisms that increase microvascular permeability in RPE, we tested whether the edema were due to free radical generation during re-expansion and reoxygenation of the collapsed lung. We used a rabbit model of RPE to test the effects of intracellular (dimethylthiourea) or extracellular (catalase) oxygen metabolite scavengers. Allopurinol was administered separately to determine whether xanthine oxidase was an important source of superoxide in this model. Edema was quantitated both gravimetrically and histologically, and lung xanthine oxidase activity was measured using a sensitive fluorometric assay with pterin as substrate. The results suggest indirectly that OH. or H2O2 (derived from O2-) contribute to the well-documented increase in lung permeability in RPE because dimethylthiourea, dimethylthiourea plus catalase, or catalase alone inhibited the edema to various degrees. Further, we observed histologically that increased numbers of neutrophils were present in re-expanded lungs and that neutrophil infiltration appeared to be diminished by antioxidant administration. Allopurinol did not decrease the edema, because xanthine oxidase activity in rabbit lung tissue is extremely low. We speculate that free radical generation in lung tissue contributes to the pathogenesis of RPE, although reinitiation of lung perfusion and ventilation requires a rapid change in intrathoracic pressure.

Enzymatic activities in the iris-ciliary body of the rabbit eye during experimentally induced acute ocular inflammation

Intravitreal injection of 5 micrograms of Shigella endotoxin, in the rabbit eye, induced an acute inflammatory response which was characterised by conjunctival hyperaemia, limbal and ciliary vascular injection, iritis, aqueous flare, miosis and reduction in intraocular pressure. Iris-ciliary body tissues, from normal and inflamed eyes, were fractionated into subcellular enriched fractions and the activities and distribution of selected enzymes were estimated. Alkaline phosphatase, a plasma membrane-bound enzyme, showed an increase in activity, whereas succinate dehydrogenase and Mn-Superoxide dismutase, both mitochondrial-bound enzymes, exhibited decreased activities. Lysosomal acid phosphatase displayed an increase in free activity and retention of latent activity inside the organelle. No alteration in free activity was shown by acid cathepsin. The cholinesterases did not exhibit any changes in activities nor did the cytosolic enzymes Cu/Zn-superoxide dismutase and lactate dehydrogenase. The decrease activity of the respiratory mitochondrial enzyme succinate dehydrogenase may contribute to the reduction in intraocular pressure, and the ability of the lysosomal organelles to retain their hydrolytic enzymes, ensures recovery of the cell from acute inflammatory attack.

Cross-clamping of the thoracic aorta. Influence of aortic shunts, laminectomy, papaverine, calcium channel blocker, allopurinol, and superoxide dismutase on spinal cord blood flow and paraplegia in baboons

There is a high incidence of paraplegia associated with thoracic aortic cross-clamping, even when cardiopulmonary bypass or shunts are used. In 56 adult baboons, spinal cord blood flow (SCBF), vascular anatomy, and paraplegia rates were evaluated. Tissue blood flow was measured by radioactive microspheres. Various procedures were used to increase SCBF and to prevent ischemia-reperfusion injury. It was found that the rate of paraplegia was inversely correlated with neural tissue ischemia (SCBF) and directly correlated with reperfusion hyperemia. Two methods completely prevented paraplegia. These two methods were a thoracic shunt with occlusion of the infrarenal aorta or cerebrospinal fluid drainage plus intrathecal papaverine injection, both of which were associated with an increased SCBF. Furthermore, papaverine dilated the anterior spinal artery (ASA) (p = 0.007) and increased the blood flow through the lower ASA. Whereas procedures utilizing a calcium channel blocker (flunarizine), allopurinol, superoxide dismutase (SOD), laminectomy alone, and a thoracoabdominal shunt not perfusing the arteria radicularis magna (ARM) all failed to prevent paraplegia, allopurinol (p = 0.026) and SOD (p = 0.004) did prevent gastric stress lesions, indicating that their failure to prevent paraplegia was not due to a lack of activity. Of great clinical interest is that, if a shunt is used and the ARM is perfused, infrarenal aortic cross-clamping increases SCBF, thus preventing paraplegia. Intrathecal application of papaverine proved to be even more effective in increasing SCBF and also completely prevented paraplegia. As this is a safer procedure than the insertion of shunts, this is the method of choice for the prevention of paraplegia associated with thoracic aortic cross-clamping. The preliminary trial using intrathecal papaverine in human beings has thus far shown no adverse side effects from the drug, and no paraplegia has occurred.

Chemotactic and candidacidal responses of rabbit alveolar macrophages during postnatal development and the modulating roles of surfactant in these responses

Chemotactic responses of alveolar macrophages from 1-, 7-, and 28-day-old rabbits to various concentrations of endotoxin-activated serum and n-formyl-methionyl-phenylalanine were tested utilizing both blind well and agarose plate assay systems. A dramatic increase in both the chemotactic response and responsiveness to various concentrations of chemoattractant was observed during postnatal maturation. The pattern of result was similar with both methods of assay. An age-related increase was also found to occur in the candidacidal activity of alveolar macrophages in contrast to their phagocytic uptake, which showed no age-related increases. Furthermore, the decreased function of macrophages from newborn animals correlated with a morphologically and biochemically less mature cell population which contained large amounts of phagocytosed surfactant-related material. Moreover, pretreatment of macrophages from 7- and 28-day-old animals with vesicles of surfactant-related material resulted in decreases in both chemotactic and candidacidal activity, with a paradoxical increase in their phagocytic activity. The resulting activities were similar to those of macrophages from 1-day-old animals treated with buffer alone. These data suggest that there is an age-related increase in the chemotactic and candidacidal activity of alveolar macrophages during maturation and that the decreased activity of macrophages from newborn animals is related in part to the large amount of surfactant-related material present at that time.

Superoxide dismutase: a cellular protective enzyme in bowel ischemia

Recent data suggest that the free-radical anion superoxide (O-2), an unstable, cytotoxic form of oxygen, is implicated in the pathogenesis of ischemic bowel injury. This study evaluates the role of superoxide dismutase (SOD), an enzyme specific for enzymatic conversion of O-2 in protecting the bowel from an ischemic insult. At laparotomy, the superior mesenteric artery was occluded for 1 min in 90-g weanling rats (n = 144). Animals were divided into four groups: I, untreated controls (n = 41); II, received aminophylline (AMN) 40 mg/kg ip, a substrate for (O-2) generation (n = 21); III, received superoxide dismutase (SOD) 2.5 mg/kg iv (n = 20); IV, received both AMN and SOD (n = 22). Rats were evaluated for bowel infarction, perforation, and mortality over a 7-day observation period. In 40 additional rats (10 per group) bowel ultrastructure was evaluated by scanning electron microscopy (EM) during occlusive ischemia and at various time intervals following reperfusion. Mortality was 63.4% in controls (26/41) with necrosis noted in 19 and perforation in 7. AMN resulted in a 90% mortality (19/21) (chi 2, P less than 0.05 vs control), with necrosis in 15 and perforation in 4. SOD reduced mortality to 25% (5/20) with necrosis in 4 and perforation in 1 (chi 2, P less than 0.02 vs controls) and, when added to AMN, 45.5% (10/22) (chi 2, P less than 0.01 vs AMN alone). On EM, tissue damage was minimal during occlusive ischemia, worsened by duration of reperfusion, enhanced by AMN, and reduced by SOD. These data suggest that following hypoxia, the injured bowel may be unable to appropriately handle reoxygenation. Tissue damage was related to duration of reperfusion and was worse following AMN, a xanthine derivative that might generate (O-2), a cytotoxic free radical. SOD detoxifies O2-, increases survival, and protects the bowel during reperfusion.

Superoxide dismutase, catalase and glutathione peroxidase activities in maternal and cord blood erythrocytes

The "antioxidant" enzymes superoxide dismutase, catalase and glutathione peroxidase were assayed in a biological model with low oxygen tension (red cells from cord blood of newborn infants). Catalase and glutathione peroxidase activities in red cells of newborns were significantly lower when compared with their mothers and with normal controls. In contrast, superoxide dismutase activity was unchanged. Thus, normal activities of superoxide dismutase seem to be necessary in order to protect red blood cells from superoxide radicals during foetal life, while even low activities of catalase and glutathione peroxidase are sufficient to protect red blood cells from hydrogen peroxide. No correlation was found between the "antioxidant" enzyme activities present in cord blood erythrocytes and the bilirubin concentrations during the first days of life.

Effects of sustained oxygen depletion on tissue pyruvate kinase activities in the freshwater turtle, Pseudemys scripta elegans

1. The effect of sustained (48 hr) oxygen depletion on tissue (brain, heart, skeletal muscle) pyruvate kinase (PyKi) activities was examined in the pond turtle (Pseudemys scripta elegans). 2. PyKi activities in skeletal muscle are significantly increased (from 322 +/- 84 to 450 +/- 95) following 48 hr of tissue hypoxia. PyKi activities in brain may already be elevated under ambient conditions but do not change following prolonged submersion (334 +/- 75 vs 325 +/- 77). Cardiac muscle PyKi is actually decreased (from 135 +/- 35 to 94 +/- 18) under anaerobic conditions. 3. The data suggest that prolonged O2 depletion may increase PyKi biosynthesis in turtle skeletal muscle (subserving enhanced glycolysis), but also demonstrate that factors other than oxygen availability are involved in the regulation of tissue PyKi activities in intact vertebrates.

Some comparative aspects of the organ distribution of superoxide dismutase activity in the freshwater turtle, Pseudemys scripta elegans

1. Superoxide dismutase activities in five tissues of the relatively anaerobic freshwater turtle were compared with SOD activities in the same tissues of two mammalian species (mouse and rabbit) with a more usual pattern of dependence on O2 availability. 2. SOD activities in brain, lung and skeletal muscle, but not liver or cardiac muscle, are significantly lower in the turtle. The turtle also shows differences in the pattern of relative SOD activities in various tissues as compared to the two mammalian species. 3. The data indicate that a relationship does exist between SOD activities and O2 exposure in intact vertebrate systems, and is consistent with a physiological role for SOD in tissue O2 metabolism.