Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neutrophils migrate to areas of inflammation and, when stimulated, produce O2-, H2O2, and other reactive O2 metabolites. To assess the effects of stimulated neutrophils on enterocytes, rat enterocytes were incubated with peripheral neutrophils. To assess cell viability, trypan blue exclusion and lactate dehydrogenase and protein release were measured. When 10(6) enterocytes/mL were incubated with 2.5 x 10(5) neutrophils/mL stimulated with phorbol myristate acetate, trypan blue exclusion decreased and lactate dehydrogenase and protein release increased. With the addition of 0.10 mg/mL of superoxide dismutase, trypan blue exclusion further decreased and lactate dehydrogenase and protein release increased. This suggests that H2O2- or H2O2/O2(-)-derived metabolites are more damaging to isolated enterocytes than O2-. To test this hypothesis, enterocytes were incubated with xanthine and increasing concentrations of xanthine oxidase in the presence and absence of superoxide dismutase. With increasing concentrations of xanthine oxidase, the cell number decreased and protein release increased. With the addition of superoxide dismutase, fewer cells were present, suggesting that cell lysis occurred. Protein release was further increased by the addition of superoxide dismutase. Enterocytes were then incubated with leucine and increasing concentrations of amino acid oxidase. With increasing concentrations of amino acid oxidase, trypan blue exclusion decreased and protein and lactate dehydrogenase release increased. These effects were ameliorated by the addition of 500 IU catalase/mL. These data suggest that O2- and H2O2, whether created by stimulated neutrophils or an enzyme-generating system, are damaging to isolated enterocytes. Superoxide dismutase did not offer enterocytes protection.
Gastroenterology 1991 Sep
PMID:Rat enterocyte injury by oxygen-dependent processes. 165 Mar 18

Metabolic redox cycling between the stilbene estrogen diethylstilbestrol (DES) and diethylstilbestrol-4',4"-quinone (DES Q) has been demonstrated previously. The xanthine and xanthine oxidase-catalyzed reduction of estrogen quinone has been studied in this work to understand the role of metabolic redox cycling in estrogen metabolism. Xanthine and xanthine oxidase catalyzed the reduction of DES Q to 44% Z-DES and 9% E-DES. This reaction was inhibited by the addition of superoxide dismutase or by a lack of oxygen (under anaerobic conditions). DES Q was also reduced in a non-enzymatic reaction by superoxide radicals generated by potassium superoxide and crown ether. The reaction between the O2-. and DES Q was also investigated by an electron spin resonance spin-trapping technique. The superoxide anion generated in an oxygen-saturated xanthine and xanthine oxidase system was detected as 5,5-dimethyl-1-pyrroline-1-oxide-superoxide adduct. The addition of DES Q or 2,3-estradiol quinone totally inhibited the formation of this adduct. The reduction of DES Q by superoxide radicals was taken as evidence that this reaction was one possible mechanism of xanthine and xanthine oxidase-mediated reduction. In addition, reduction of DES Q by direct electron transfer to quinone by the enzyme may also occur. The intermediate formation of semiquinone free radicals in the reduction is implied by the nature of the single electron transfer reactions and, in addition, has been demonstrated for the catechol estrogen by electron spin resonance measurements. It is concluded that the reduction of estrogen quinones to their hydroquinones by xanthine oxidase occurs by both one electron transfer to the quinone and by formation of superoxide which then reduces the quinone.
Biochem Pharmacol 1991 Sep 27
PMID:Xanthine oxidase-catalyzed reduction of estrogen quinones to semiquinones and hydroquinones. 165 92

Oxygen radical generation in the xanthine- and NADH-oxygen reductase reactions by xanthine oxidase, was demonstrated using the ESR spin trap 5,5'-dimethyl-1- pyrroline-N-oxide. No xanthine-dependent oxygen radical formation was observed when allopurinol-treated xanthine oxidase was used. The significant superoxide generation in the NADH-oxygen reductase reaction by the enzyme was increased by the addition of menadione and adriamycin. The NADH-menadione and -adriamycin reductase activities of xanthine oxidase were assessed in terms of NADH oxidation. From Lineweaver-Burk plots, the Km and Vmax of xanthine oxidase were estimated to be respectively 51 microM and 5.5 s-1 for menadione and 12 microM and 0.4 s-1 for adriamycin. Allopurinol-inactivated xanthine oxidase generates superoxide and OH.radicals in the presence of NADH and menadione or adriamycin to the same extent as the native enzyme. Adriamycin radicals were observed when the reactions were carried out under an atmosphere of argon. The effects of superoxide dismutase and catalase revealed that OH.radicals were mainly generated through the direct reaction of H2O2 with semiquinoid forms of menadione and adriamycin.
J Biochem 1991 Sep
PMID:Allopurinol-insensitive oxygen radical formation by milk xanthine oxidase systems. 166 14

A technique for the separation of neutrophils from macrophages-epithelial cells in samples of nonmastitic bovine milk with low cell counts has been developed. The procedure is based on centrifugation in a discontinuous metrizamide gradient and is rapid, taking less than 40 min. The recovery of the neutrophils is about 30% and their viability about 90%. The isolated neutrophils showed an appreciable unstimulated luminol- and lucigenin-dependent chemiluminescence, which was due to NADPH oxidase rather than to xanthine oxidase. The neutrophils had a higher rate of ingestion of C3-opsonized particles than macrophages-epithelial cells, whereas no significant differences in phagocytosis of IgG-opsonized yeast or unopsonized yeast were detected between the two cell populations. The macrophages-epithelial cells produced no luminol-dependent chemiluminescence and induced considerably lower activity in the lucigenin-dependent system than neutrophils, indicating that these cells contain no myeloperoxidase. Analyses of the activity of the neutrophils in response to C3-opsonized yeast particles showed that the luminol-dependent chemiluminescence of cells isolated from residual milk increased significantly over the lactation period. Moreover, a tendency to a higher phagocytosis and chemiluminescence of neutrophils isolated from residual milk than from stripping milk was indicated.
J Dairy Sci 1991 Sep
PMID:Isolation and phagocytic properties of neutrophils and other phagocytes from nonmastitic bovine milk. 172 16

The rates of NADH oxidation in presence of xanthine oxidase increase to a small and variable extent on addition of high concentrations of lactate dehydrogenase and other dehydrogenases. This heat stable activity is similar to polyvanadate-stimulation with respect to pH profile and SOD sensitivity. Isocitric dehydrogenase (NADP-specific) showed heat labile, SOD-sensitive polyvanadate-stimulated NADH oxidation activity. Polyvanadate-stimulated SOD-sensitive NADH oxidation was also found to occur with riboflavin, FMN and FAD in presence of a non-specific protein, BSA, suggesting that some flavoproteins may possess this activity.
Mol Cell Biochem 1991 Sep 18
PMID:Stimulation of NADH oxidation by xanthine oxidase and polyvanadate in presence of some dehydrogenases and flavin compounds. 178 72

In cytosolic fraction of adult Paragonimus westermani, superoxide dismutase activity was identified (4.3 units/mg of specific activity) using a xanthine-xanthine oxidase system. The enzyme was purified 150 fold in its activity using the ammonium sulfate precipitation, DEAE-Trisacryl M anion-exchange chromatography and Sephadex G-100 molecular sieve chromatography. The enzyme exhibited the enhanced activity at pH 10.0. The enzyme activity totally disappeared in 1.0mM cyanide while it remained 77.8% even in 10 mM azide. These findings indicated that the enzyme was Cu, Zn-SOD type. Molecular mass of the enzyme was estimated to be 34 kDa by gel filtration and 17 kDa on reducing SDS-polyacrylamide gel electrophoresis which indicated a dimer protein.
Kisaengchunghak Chapchi 1991 Sep
PMID:Purification and characterization of a Cu, Zn-superoxide dismutase from adult Paragonimus westermani. 178 52

A series of experiments have been done to investigate the role of oxygen free radicals in ischemia/reperfusion injury. The following results were found: Myocardial MDA content increased significantly after post-ischemic reperfusion in vivo and in vitro. A blockade of the xanthine oxidase pathway for free radical generation could provide effective protection against ischemia/reperfusion injury. Exogenous reactive oxygen intermediates H2O2, .OH and O2- could induce changes in the contractility and electrophysiological properties of myocardial cells similar to those seen in ischemia/reperfusion. An outburst of free radical generation was detected by ESR spectroscopy at low temperature (-173 degrees C) and with the spin trapping technique during the very early phase of reperfusion. The authors emphasize the important role of free radicals in the pathogenesis of myocardial ischemia/reperfusion injury.
Chin Med Sci J 1991 Sep
PMID:The role of oxygen free radicals in myocardial ischemia/reperfusion injury. 179 73

The plasma malonaldehyde (MDA), xanthine oxidase (XO) and uric acid (UA) levels and erythrocyte superoxide dismutase (SOD) were measured in 10 cases during cardiopulmonary bypass (CPB) operation. These examinations were taken at pre-aortic clamping, 15 min after aortic clamping, 30, 60, 120 and 180 min after reperfusion respectively. The results showed that MDA, XO and UA rise but SOD decreases after reperfusion. We believe that a lot of oxygen free radicals (OFR) release during peri-operative period and the XO may be an important pathway of OFR release.
Hua Xi Yi Ke Da Xue Xue Bao 1991 Sep
PMID:[Consecutive observation of the plasma MDA, XO and UA levels and erythrocyte SOD in 10 cases of cardiopulmonary bypass]. 181 15

Many reports concerning the involvement of active oxygen free radicals in the pathogenesis and progression of acute pancreatitis have been published. In this study, the direct toxic effect of active oxygen free radicals on the rat pancreas was evaluated in vivo. Superoxide anions, generated via the xanthine/xanthine oxidase (X/XO) system, and hydrogen peroxide (H2O2) were used. After continuous arterial injection of X/XO into the celiac artery hemorrhage and extensive edema developed. However, additional continuous injection of superoxide dismutase (SOD) into the external jugular vein completely suppressed the hemorrhage and relieved the edema. When hydrogen peroxide (100 microM/Kg/hour) was injected continuously through the celiac artery made hemorrhage and edema were recognized in the pancreas, both of which were suppressed by continuous injection of catalase (10 mg/Kg/hour) or gabexate mesilate (10 mg/Kg/hour) into the external jugular vein. The amylase and lipase levels in the intraperitoneal fluid rose to more than 10 times the preoperative values 5 hours after drug administration. These levels were lowered to 2 times the preoperative values by the continuous venous injection of SOD or catalase (which are specific scavengers of superoxide anions or hydrogen peroxide, respectively) or by gabexate mesilate. On the other hand, serum amylase and lipase levels remained almost constant throughout the entire experiment. Thus, the administration of active oxygen free radicals caused acute pancreatitis, which was suppressed by the systemic administration of specific scavengers for each free radical. Active oxygen free radicals were shown to have a direct, toxic effect on the pancreas.
Nihon Geka Hokan 1991 Sep 01
PMID:[Effect of oxygen free radicals on the rat pancreas in vivo]. 182 4

Reperfusion after reversible ischemia has been shown to result in prolonged depression of contractile function ("myocardial stunning"). Recent studies suggest that oxygen free radicals may mediate postischemic dysfunction. Since heart sarcolemmal membranes, which contain several types of enzymes, ion channels and receptors play important roles to maintain cell functions, the present study was undertaken to examine the effects of oxygen free radicals on heart sarcolemmal membrane functions in vitro. In the presence of a superoxide anion radical-generating system (2mM xanthine plus 0.03 U/ml xanthine oxidase), sarcolemmal Ca(2+)-stimulated ATPase activity and ATP-dependent Ca2+ accumulation were inhibited in an incubating time-dependent manner. Both lipid peroxidation (r = 0.82) and sulfhydryl group content (r = 0.95) showed significant correlations with Ca(2+)-stimulated ATPase activity. ATP-independent Ca2+ bindings were increased upon treating the membranes with xanthine plus xanthine oxidase. Voltage-dependent Ca(2+)-channels were also affected by oxygen free radicals. The maximal number of binding sites (Bmax) for [3H]-nitrendipine binding was depressed without any changes in dissociation constant (Kd). The effects of oxygen free radicals on adrenergic receptors were more complex. Bmax for [3H]-dihydroalprenolol (DHA) binding (beta-receptor) was increased whereas Bmax for [3H]-prazosin binding [alpha 1-receptor) was decreased after incubating the membrane with xanthine plus xanthine oxidase. Kd for [3H]-DHA or [3H]-prazosin binding was increased. Superoxide dismutase showed protective effects on the changes in these membrane functions due to xanthine plus xanthine oxidase. It is suggested that oxygen free radicals damage heart sarcolemmal membrane functions which may lead to cardiac dysfunction in the stunned myocardium.
Jpn Circ J 1991 Sep
PMID:Stunned myocardium and oxygen free radicals--sarcolemmal membrane damage due to oxygen free radicals. 183 72


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