Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Treated carbon fiber electrodes were used with differential normal pulse voltammetry (DNPV) for in vivo determination of the relative participation of uric acid (UA) to peak 3 derived between 250-300 mV in the dorsal horn of the spinal cord of anesthetized rats. In vitro, treated carbon fiber electrodes respond linearly over a large range of concentrations of UA (oxidation potential around 250 mV) and 5-hydroxyindoleacetic acid (5-HIAA, oxidation potential around 280-290 mV), but are 3 to 4 times more sensitive to 5-HIAA than to UA. In vivo the question remains as to the exact nature of peak 3 because the difference between oxidation potentials of UA and 5-HIAA is not great enough to permit a separate monitoring of the two compounds. In normal rats, administration of the xanthine oxidase inhibitor allopurinol, produced a progressive decrease of the signal, which reached 64.3% of controls at 120 min (35.6% diminution) after injection, and then plateaued around this value for up to 2 h. The administration of the monoamine oxidase inhibitor (MAOI) clorgyline, produced a classical decay in the voltammograms due to a diminution of endogenous 5-HIAA; however, allopurinol injected 3 h after MAOI gave an additional decrease of peak 3 of about 28%. Finally, in rats pretreated with parachlorophenylalanine (pCPA), the residual peak (32.48% as compared to peak 3 of normal rats taken as 100%), the potential of which is shifted to near that of UA, could be decreased by allopurinol to a level of 9.6% of the peak in control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Brain Res 1987 Sep 01
PMID:In vivo electrochemical detection of 5-hydroxyindoles in the dorsal horn of the spinal cord: the contribution of uric acid to the voltammograms. 244 20

The effects of various pesticides (lindane, binapacrile and parathion) on the content of cytochrome P450 and glutathione, and on the activity of lipoperoxidase, xanthine oxidase and transaminases (SGOT and SPGT) were examined. Other parameters, such as the relative liver mass and hepatocyte viability were also estimated. All the studied parameters in the liver homogenate and in hepatocytes were changed by binapacrile, whereas in blood only the glutathione level was altered. Lindane produced an effect on all the parameters. In hepatocytes it did not affect only the lipoperoxidase activity. In the blood it changed only the level of glutathione content. Parathion, in the liver homogenate, changed all of the parameters examined, whereas in hepatocytes only lipoperoxidase activity remained unchanged. In the blood parathion caused a slight increase in the sulphhaemoglobin level and decreased the glutathione content.
Arh Hig Rada Toksikol 1989 Sep
PMID:[Pesticides and liver biochemistry]. 248 16

The reported presence of covalently bound phosphate residues in flavoproteins has significant implications with regard to the catalytic mechanisms and structural stability of the specific enzymes themselves and in terms of general cellular metabolic regulation. These considerations have led to a reevaluation of the presence of covalently bound phosphorus in the flavoproteins xanthine oxidase (xanthine: oxygen oxidoreductase, EC 1.1.3.22) and glucose oxidase (beta-D-glucose: oxygen 1-oxidoreductase, EC 1.1.3.4). Milk xanthine oxidase purified by a procedure that includes anion-exchange chromatography is shown to contain three phosphate residues. All three are noncovalently associated with the protein, two with the FAD cofactor, and one with the molybdenum cofactor. Results of chemical analysis and 31P NMR spectroscopy indicate that enzyme purified by this method contains no phosphoserine residues. Xanthine oxidase preparations purified by chromatography on calcium phosphate gel in place of DEAE-Sephadex yielded higher phosphate-to-protein ratios, which could be reduced to the expected values by additional purification on a folate affinity column. Highly active, highly purified preparations of glucose oxidase are shown to contain only the two phosphate residues of the FAD cofactor. The covalently bound bridging phosphate reported by others may arise in aged or degraded preparations of the enzyme but appears not to be a constituent of functional glucose oxidase. These results suggest that the presence of covalent phosphate residues in other flavoproteins should be rigorously reevaluated as well.
Proc Natl Acad Sci U S A 1989 Sep
PMID:Covalently bound phosphate residues in bovine milk xanthine oxidase and in glucose oxidase from Aspergillus niger: a reevaluation. 250 51

Involvement of free radicals and their scavenging enzymes in mice pulmonary thromboembolism, induced by intravenous infusion of collagen and adrenaline, has been studied. Malonaldehyde (MDA) and activities of xanthine oxidase (XO), catalase (CAT) and superoxide dismutase (SOD) were estimated in platelets, heart and lung homogenates. MDA increased in all the tissues sharply, while animals showed 70-80% thrombocytopenia. Xanthine oxidase activity in these animals increase significantly in heart. However, increased SOD activity and decreased catalase activity was observed in platelets. Intravenous administration of superoxide dismutase (5 mg/kg), catalase (5 mg/kg) and mannitol (200 mg/kg) protected the mice against pulmonary thromboembolism. The importance of free radicals in mice pulmonary thromboembolism has been demonstrated.
Thromb Res 1989 Sep 01
PMID:Role of free radicals in pulmonary thromboembolism in mice. 251 Mar 58

The role of platelet glucose-6-phosphate dehydrogenase (G-6-PD) in mediating the effects of human platelets on oxidant-induced edema in the isolated perfused rabbit lung was investigated using dehydroepiandrosterone, a specific steroidal inhibitor of G-6-PD. Xanthine oxidase (0.003 and 0.012 U/ml) caused lung edema that was attenuated by coinfusion of washed human platelets. Platelets that were incubated with DEA to inhibit G-6-PD activity augmented xanthine oxidase-induced lung edema and pulmonary hypertension at both doses of xanthine oxidase. Infusion of papaverine to maintain stable pulmonary artery (PA) pressures, incubation of G-6-PD-inhibited platelets with acetylsalicylate, or infusion of a thromboxane-prostaglandin endoperoxide receptor site antagonist, SQ 29548, into the lung perfusate prevented augmentation of lung edema and the PA pressor response by G-6-PD-inhibited platelets. It was concluded that antioxidant-intact platelets attenuate oxidant-induced lung edema by preventing increased membrane permeability, and that G-6-PD-inhibited platelets augment lung edema through hydrostatic mechanisms mediated by release of platelet cyclooxygenase products.
J Clin Invest 1989 Sep
PMID:Human platelets modulate edema formation in isolated rabbit lungs. 252 53

Xanthine oxidase activity in the rat brain was measured by means of high-performance liquid chromatography with electrochemical detection of uric acid. Cerebral ischemia was produced by a four-vessel occlusion method. In the control rat, the enzyme activity was 0.87 +/- 0.13 nmol/gm wet weight/min at 25 degrees C (mean +/- standard deviation), of which 92.4% was associated with the nicotinamide adenine dinucleotide (NAD)-dependent dehydrogenase form and only 7.6% with the oxygen-dependent superoxide-producing oxidase form. However, the ratio of the latter form increased to 43.7% after 30 minutes of global ischemia, despite the total xanthine oxidase activity remaining the same. Thus, it was revealed that uric acid can be synthesized in the rat brain and that cerebral ischemia induced the conversion of xanthine oxidase from an NAD-dependent dehydrogenase to an oxygen-dependent superoxide-producing oxidase. Although the xanthine oxidase pathway has been proposed as a source of oxygen-derived free radicals in various ischemic organs other than brain, the results of the present study suggest the involvement of the oxygen free radicals generated from this pathway in the pathogenesis of the ischemic injury of the rat brain.
J Neurosurg 1989 Sep
PMID:Changes in xanthine oxidase in ischemic rat brain. 254 24

Cell injury from hyperoxia is associated with increased formation of superoxide radicals (O2-). One potential source for O2- radicals is the reduction of molecular O2 catalyzed by xanthine oxidase (XO). Physiologically, this reaction occurs at a relatively low rate, because the native form of the enzyme is xanthine dehydrogenase (XD) which produces NADH instead of O2-. Reports of accelerated conversion of XD to XO, and increased formation of O2- formation in ischemia-reperfusion injury, led us to examine whether hyperoxia, which is known to increase O2- radical formation, is associated with increased lung XO activity, and accelerated conversion of XD to XO. We exposed 3-month-old rats either to greater than 98% O2 or room air. After 48 h, we sacrificed the rats and measured XD and XO activities and uric acid contents of the lungs. We also measured the activities of the two enzymes in the heart as a control organ. We found that the activity of XD was not altered significantly by hyperoxia in rat lungs or hearts, but XO activity was markedly lower in the lung, whether expressed per whole organ or per milligram protein, and remained unchanged in the heart. Lung uric acid content was also significantly lower with hyperoxia. The decrease in lung XO activity may reflect inactivation of the enzyme by reactive O2 metabolites, possibly as a negative feedback mechanism. The concomitant decrease in uric acid content suggests either decreased production mediated by XO due to its inactivation or greater utilization of uric acid as an antioxidant. We examined these postulates in vitro using a xanthine/xanthine oxidase system and found that H2O2, but not uric acid, has an inhibitory effect on O2- formation in the system. We therefore conclude that hyperoxia is not associated with increased conversion of XD to XO, and that the exact contribution of XO to hyperoxic lung injury in vivo remains unclear.
Arch Biochem Biophys 1989 Sep
PMID:Hyperoxia and xanthine dehydrogenase/oxidase activities in rat lung and heart. 254 69

As guinea-pig pulmonary macrophages (PM) synthesize the linoleic acid metabolite 9-hydroxy-octadecadienoic acid (9-OH-Lin) under non-stimulated conditions in relatively large quantities, we investigated whether this product has an effect on the macrophage's own phagocytic cell function. 9-OH-Lin, and also its hydroperoxy precursor 9-hydroperoxy-octadecadienoic acid (9-OOH-Lin), influenced the generation of PM chemiluminescence, a measure of the production of reactive oxygen species. The generation of lucigenin-enhanced chemiluminescence by stimulated and non-stimulated PM was inhibited concentration-dependently. Inhibition was observed at concentrations as low as 10 nM. Since 9-OH-Lin and 9-OOH-Lin also inhibited the generation of chemiluminescence by a cell-free enzyme system, i.e. xanthine/xanthine oxidase, the inhibitory effects might represent a scavenging activity towards reactive oxygen species. 9-OH-Lin and 9-OOH-Lin did not influence other phagocytic cell functions, e.g. PM phagocytic capacity, the aggregatory response to the calcium ionophore A23187, or the release of lysosomal enzymes. The effects of 9-OH-Lin and 9-OOH-Lin could be ascribed to the hydroxy and hydroxyperoxy moiety, respectively, as evidenced by lack of effect of the native fatty acid linoleic acid. We conclude that the formation of 9-OH-Lin and 9-OOH-Lin by PM may represent a regulatory mechanism towards the cell's own activity by modulating reactive oxygen species.
Eur J Biochem 1989 Sep 01
PMID:Modulatory activity of 9-hydroxy- and 9-hydroperoxy-octadecadienoic acid towards reactive oxygen species from guinea-pig pulmonary macrophages. 255 Feb 27

Free radical formation was studied with electron spin resonance during 2 h of intestinal ischemia in the cat, at a blood flow less than 5 ml.min-1.100 g-1, followed by 30-min reperfusion. A modification of the spin trapping technique was used to stabilize highly reactive free radicals. The rate of secondary radical formation was 0.32 +/- 0.06 mumol.min-1.100 g intestine-1 before ischemia and increased to a maximum of 0.66 +/- 0.09 mumol.min-1.100 g-1 during the first minutes of reperfusion (mean +/- SE, n = 5). This could be prevented either by maintaining intestinal blood flow at 8-15 ml.min-1.100 g-1, by administering allopurinol before and during ischemia, or by perfusing the intestinal lumen with an O2-saturated buffer solution during ischemia, resulting in maximum rates of radical production during reperfusion of 0.37 +/- 0.04 (n = 6), 0.33 +/- 0.04 (n = 5), and 0.39 +/- 0.13 mumol.min-1.100 g-1 (n = 5), respectively. The results demonstrate that free radicals are produced in the intestine during reperfusion after a period of reduced blood flow below a certain critical level, and that inhibition of xanthine oxidase and prevention of hypoxia will eliminate this radical production.
Am J Physiol 1989 Sep
PMID:Radical production during in vivo intestinal ischemia and reperfusion in the cat. 255 Nov 84

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.
Am J Physiol 1989 Sep
PMID:Mechanism for depression of heart sarcolemmal Ca2+ pump by oxygen free radicals. 255 Nov 90


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