Effects Of Oxygen Free Radicals Research Articles

Effect of oxygen free radicals on corneal collagen.

Corneal collagen was labeled in vivo by injection of 14C-proline into the anterior chamber of rabbit eyes. The isolated corneal collagen was incubated in iron-free phosphate buffered saline (pH 7.4) containing 1 mM ascorbate and 0.1 mM CuSO4 for either 1 hour or 3 hours at 37 degrees. Addition of 2 volumes of 8M urea-1 mM dithiothreitol and heating for 1 min at 100 degrees solubilized virutually all of the collagen in the control incubations but left a significant amount of insoluble collagen in specimens exposed to the hydroxyl radical generating system. This residue amounted to 19% and 38% of the initial radioactivity in samples incubated for 1 h and 3 h, respectively. The chromatographic profiles (gel filtration on CL-4B) of the soluble fraction showed an increase in both aggregation and degradation products of collagen in the 1 h incubation mixture, whereas after 3 h there was an increase only in degradation products. These observations suggest that additional crosslinking of the soluble collagen aggregates observed at 1 h may be responsible for their subsequent disappearance at 3 h, with concomitant increase of the insoluble fraction. Collagen degradation by .OH may play a role in corneal ulceration, whereas hydroxyl radical-mediated crosslinking is consistent with age-dependent increases in insoluble collagen.

Effects of oxygen free radicals on cardiovascular function and myocardial noradrenaline release: R. Chahine, X. Chen, N. Campeau, J. de Champlain, R. Nadeau. Centre de recherche, Hoˆpital du Sacré-Coeur, Universitéde Montréal, Québec, Canada

Effects of oxygen free radicals on cardiovascular function and myocardial noradrenaline release: R. Chahine, X. Chen, N. Campeau, J. de Champlain, R. Nadeau. Centre de recherche, Hoˆpital du Sacré-Coeur, Universitéde Montréal, Québec, Canada

Is malondialdehyde a marker of the effect of oxygen free radicals in rat heart tissue?

We tested the effect of exogenous purine derived free radicals and H2O2 VS ischemia and reperfusion on the thiobarbituric-acid (TBA)-reactive material and malondialdehyde (MDA) formation in isolated rat hearts using the thiobarbituric acid test and high performance lipid chromatography (HPLC). We could not detect increased thiobarbituric-acid-reactive material or MDA- production during 6 MM H2O2 infusion, during free radical generation by purine-derived free radicals, or using ischemia and reperfusion. Increased thiobarbituric-acid-reactive material and MDA tissue levels were detected only during infusion of 12 mM H2O2 (p<0.001). We conclude that the generally used thiobarbituric acid assay for MDA is susceptible to artifacts and unsuited as an indirect measure for low-to-medium-levels of oxygen free radicals. Using HPLC assay, which accurately measures MDA, no evidence was found that MDA is a primary and direct lipid peroxidation product of exogenous or endogenous reactive oxygen species.

Cardiodepressive (CD) and cardiotoxic (CT) effects of oxygen free radicals (OFR) in cultured heart muscle cells

Cardiodepressive (CD) and cardiotoxic (CT) effects of oxygen free radicals (OFR) in cultured heart muscle cells

Effect of oxygen free radicals, hypoxia and pH on the release of liver lysosomal enzymes

We investigated the effect of acidic environment, hypoxia and oxygen free radicals on the release of beta-glucuronidase from rat liver lysosomes. A lysosomal enriched fraction from the homogenate of rat liver was prepared, using differential centrifugation technique. Exogenous oxygen free radicals were generated using xanthine-xanthine oxidase system. The release of beta-glucuronidase activity was measured from the lysosomes. The lysosomal fraction was exposed to various pH (8.0, 7.4, 6.5, 6.0, 5.5) and pO2 (454, 172, 96, 57,34 mm Hg) separately or to a combination of low pH (5.5, 6.5) and low pO2 (34, 57 mm Hg). The changes in pH or pO2 separately did not cause any increase in the release of beta-glucuronidase activity. The presence of oxygen free radicals at each pH or pO2 resulted in about a 3-fold increase in the release of beta-glucuronidase. A combination of very low pO2 and pH (pO2 (mm Hg)/pH; 34/5.5, 34/6.5) resulted in an increased release of beta-glucuronidase from lysosomes. Oxygen free radicals in the presence of both low pO2 and pH resulted in a further increase in the release of beta-glucuronidase. These data indicate that oxygen free radicals and not the alterations in pH and/or pO2 are primarily responsible for the disruption of lysosomes.

Differential electrophysiological effects of oxygen free radicals on canine Purkinje fibers and papillary muscles

Differential electrophysiological effects of oxygen free radicals on canine Purkinje fibers and papillary muscles

Effect of oxygen free radicals on cardiac contractile proteins

Effect of oxygen free radicals on cardiac contractile proteins

Effects of oxygen free radicals on human erythrocytes: protective effects of deferoxamine and allopurinol

Effects of oxygen free radicals on human erythrocytes: protective effects of deferoxamine and allopurinol

Inhibition of cardiac phosphatidylethanolamine N-methylation by oxygen free radicals

This study was undertaken to examine the effects of oxygen free radicals on phosphatidylethanolamine (PE) N-methylation in rat heart sarcolemmal (SL) and sarcoplasmic reticular (SR) membranes. Three catalytic sites involved in the sequential methyl transfer reaction were studied by assaying the incorporation of radiolabeled methyl groups from S- adenosyl- l-methionine (0.055, 10, and 150 μM) into SL or SR PE molecules under optimal conditions. In the presence of xanthine + xanthine oxidase (superoxide anion radicals generating system), PE N-methylation was inhibited at site I and III in the heavy SL fraction isolated by the hypotonic shock-LiBr treatment method. In the light SL fraction isolated by sucrose-density gradient, a significant inhibition of PE N-methylation was seen at all three sites. These inhibitory effects of xanthine + xanthine oxidase on PE N-methylation were prevented by the addition of superoxide dismutase. Hydrogen peroxide showed a significant inhibition of PE N-methylation at site I in the heavy SL fraction, and at site I and II in the light SL fraction. Catalase blocked the inhibitory effects of hydrogen peroxide. The effects of both xanthine + xanthine oxidase and hydrogen peroxide on the SR membranes were similar to those seen for the heavy SL fraction. These results suggest that, in addition to lipid peroxidation, the oxygen free radicals may affect the function of cardiac membranes by decreasing the phospholipid N-methylation activity.

Alterations in heart sarcolemmal Ca2+-ATPase and Ca2+-binding activities due to oxygen free radicals

Effects of oxygen free radicals on Ca2+/Mg2+ ATPase and ATP-independent Ca2(+)-binding activities were examined in rat heart sarcolemma. Membranes were incubated with different oxygen radical generating media such as xanthine + xanthine oxidase, hydrogen peroxide, and hydrogen peroxide + Fe2+. In the presence of xanthine + xanthine oxidase, Ca2+ ATPase activity was stimulated and this effect was prevented by the addition of superoxide dismutase. Hydrogen peroxide also showed a significant increase in Ca2(+)-ATPase activity in a dose-dependent manner and this effect was blocked by catalase. On the other hand, a combination of hydrogen peroxide + Fe2+ decreased Ca2(+)-ATPase activity; this depression was prevented by the addition of D-mannitol. The observed change in Ca2(+)-ATPase activity due to oxygen free radicals was associated with changes in Vmax, whereas Ka remained unaffected. Both xanthine + xanthine oxidase and hydrogen peroxide increased whereas, hydrogen peroxide + Fe2+ inhibited the ATP-independent Ca2(+)-binding activities. It is suggested that oxygen free radicals may influence Ca2+ movements in the cell by altering the Ca2+/Mg2+ ATPase and Ca2(+)-binding activities of the membrane and these effects may be oxygen-radical species specific.

O-101 - Effect of free oxygen radicals on endothelium-dependent relaxation of coronary artery

O-101 - Effect of free oxygen radicals on endothelium-dependent relaxation of coronary artery

Lipid peroxidation and activity of antioxidant enzymes in muscle of the lower leg before and after arterial reconstruction

Reperfusion syndrome and lipid peroxidation due to toxic effects of free oxygen radicals might be one pathophysiological cause of the oedema that develops during the first week after a femoro-popliteal reconstruction. This paper reports the activity of the protecting antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase and catalase in gastrocnemic muscle before and after reperfusion of chronically ischaemic legs with comparison to activities in non-ischaemic muscle. Furthermore the susceptibility to lipid peroxidation in the muscle was measured as thiobarbituric acid reactive material (TBAR). The activities of CuZn SOD, Mn SOD and glutathione peroxidase were equal in normally perfused and chronically ischaemic muscle and there was no difference after reperfusion. Muscle catalase activity was low compared to activity of red blood cells and could not be reliably estimated. There was no difference in iron-stimulated lipid peroxidation of ischaemic and non-ischaemic muscle but in reliably estimated. There was no difference in iron-stimulated lipid peroxidation of ischaemic and non-ischaemic muscle but in muscle biopsied 10 min after reperfusion there was a significant increase in production of TBAR indicating an increased susceptibility for lipid peroxidation at this time. The finding is compatible with the occurrence of an oxidant insult on the muscle at reperfusion. Ischaemia--or reperfusion--induced reductions in activity of antioxidant enzymes are however not related to this reaction.

Reduction of calcium channel antagonist binding sites by oxygen free radicals in rat heart

In view of the importance of Ca 2+-channels in controlling the entry of Ca 2+ into the myocardium, this study was undertaken to examine the effects of oxygen free radicals on the binding of Ca 2+-channel antagonists in rat heart by employing [ 3H]-nitrendipine as a ligand. Isolated heart membranes were incubated with xanthine + xanthine oxidase (a superoxide anion radicals generating system), hydrogen peroxide (an activated species of oxygen), or hydrogen peroxide + Fe 2+ (a hydroxyl radicals generating system). The assay of the [ 3H]-nitrendipine binding activity revealed that the maximal number of binding sites ( B max) were reduced in a time-dependent manner by superoxide radicals without any changes in the binding constant ( K d); a significant reduction of B max was seen after incubating membranes with xanthine + xanthine oxidase for a 10-min-period. Superoxide dismutase showed a protective effect on the superoxide radicals induced reduction in B max. Both hydrogen peroxide and hydroxyl radicals also depressed the B max for [ 3H]-nitrendipine binding without any significant change in K d; catalase and mannitol showed protective effects on hydrogen peroxide or hydroxyl radicals induced depression in B max, respectively. These results indicate that oxygen free radicals may reduce the number of Ca 2+-channels in the cell membrane and this change may contribute towards decreasing the voltage-dependent Ca 2+ influx in the cardiac cell.

Mechanism for depression of heart sarcolemmal Ca2+ pump by oxygen free radicals

To understand the involvement of changes in sulfhydryl groups in causing depression of the sarcolemmal Ca2+-pump activities, this study was undertaken to examine the effects of oxygen free radicals on rat heart sarcolemmal sulfhydryl groups, Ca2+-stimulated adenosinetriphosphatase (ATPase), and ATP-dependent Ca2+ accumulation. In addition, the effects of sulfhydryl reagents such as dithiothreitol, cysteine, and N-ethylmaleimide on Ca2+-pump activities were investigated. The inhibition of sarcolemmal Ca2+-pump activities by O2-. (xanthine + xanthine oxidase) and H2O2 was decreased by the addition of dithiothreitol or cysteine in a dose-dependent manner. N-ethylmaleimide also showed inhibitory effects on Ca2+-pump activities both in a dose- and time-dependent manner; dithiothreitol and cysteine prevented changes in Ca2+-pump activities because of N-ethylmaleimide. Heart sarcolemmal sulfhydryl groups were depressed by O2-., H2O2, and .OH (H2O2 + Fe2+) both in a dose- and time-dependent manner. Superoxide dismutase, catalase, and D-mannitol showed protective effects on the sulfhydryl group depression by O2-., H2O2, and .OH, respectively. A significant correlation between changes in sarcolemmal Ca2+-stimulated ATPase activity and sarcolemmal sulfhydryl groups was seen. These results indicate that oxygen free radicals may depress the heart sarcolemmal Ca2+-pump activities by modifying the sulfhydryl groups in the sarcolemmal membrane.

Effects of free radicals produced by sonolysis on ubiquinone-containing vesicles

The aim of this study was to evaluate both the effect of oxygen free radicals produced by ultrasonic irradiation on ubiquinone-3 incorporated into egg phosphatidylcholine vesicles and lipid peroxidation of the same vesicles. Owing to water sonolysis, degradation of polyunsaturated fatty acid residues occurred when model membranes were sonicated in the absence of ubiquinone. Under these conditions, Hepes buffer, but not formate, was able to protect against HO − damage, probably because access to the site of HO − formation is easier for the buffer. Incorporation of quinone prevented peroxidation due to HO − radicals, with a concomitant decrease of ubiquinone content. Experiments performed to evaluate the effects of varying egg phosphatidylcholine concentration on conjugated diene formation and ubiquinone stability suggest that the antioxidant effect of this compound mostly resides in its capacity to act as a ‘chain-breaker’ antioxidant.

Effect of oxygen free radicals on myocardial microsomal membrane integrity

Effect of oxygen free radicals on myocardial microsomal membrane integrity

Effect of oxygen free radicals on cardiovascular function at organ and cellular levels

Oxygen free radicals (OFR) have been implicated as a causative factor of cell damage in several pathologic conditions. It is possible that OFR could have effects on cardiac function and contractility. The present investigation deals with the effects of OFR in the absence and in the presence of scavangers of OFR (superoxide dismutase and catalase) on cardiac function, index of cardiac contractility, serum creatine kinase (CK), and blood lactate, Po 2 and pH in the anesthetized dogs. The hemodynamic measurements and collection of blood samples for measurement of CK, lactate, Po 2 and pH were made before and at various intervals after administration of OFR for 1 hour. Xanthine and xanthine oxidase were used to generate OFR. OFR produced a decrease in cardiac function and indices of myocardial contracility and an increase in the serum CK. OFR produced an increase in the systemic and pulmonary vascular resistance. Although there was a tendency for an increase in the blood lactate, the increase was not significant. The blood Po 2 and pH were not affected. Superoxide dismutase (SOD), alone or in combination with catalase, tended to protect cardiac function against the deleterious effects of OFR. Scavangers of OFR prevented the OFR-induced rise in serum CK. Although the protective effect of SOD plus catalase was slightly better than SOD alone, the results were not significantly different from each other. These results suggest that OFR are cardiac depressant and increase the peripheral vascular resistance besides causing cellular damage. Scavangers of OFR may be beneficial in counteracting the deleterious effects of OFR on hemodynamic parameters and cellular integrity.

Effects of oxygen free radicals on membrane fluidity of human erythrocytes

Effects of oxygen free radicals on membrane fluidity of human erythrocytes

Assessment of superoxide-mediated release of vascular-inhibitory factor(s) from endothelial cells by using a two-bath system

Release of a vascular-inhibitory factor from endothelial cells (EC), different from endothelium-derived relaxant factor (EDRF), was identified through use of a two-bath system. This two-bath system precluded the effects of oxygen-free radicals that appear when electrical field stimulation (EFS) is directly imposed on detector muscle.

The effects of oxygen free radicals on the carbohydrate moiety of IgG

The CH2-linked glycoform of rheumatoid IgG is abnormal in having a reduced galactose content. This has been postulated to be a synthetic defect due to a decrease in the level of rheumatoid B cell galactosyltransferase. However, more recent work has indicated that agalactosylation may be common to chronic inflammatory diseases. In this work we have investigated the effect of oxygen free radicals (OFRs), which are generated by activated phagocytic cells at inflammatory sites, on the carbohydrate moiety of IgG. Radiolytically generated peroxy (ROO •) and hydroxyl radicals (OH •) but not superoxide anion radicals (O— 2 −) were found to destroy galactose on IgG. After OH • attack, this was associated with an increase in the availability of N-acetylglucosamine, possibly due to its presence as a terminal residue. These results suggest that the agalactosylation associated with chronic inflammation may not only be synthetic in nature, but may also be a consequence of post-synthetic degradation by OFRs.