Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Metastases in rat liver were generated experimentally by intraportal injection of colon cancer cells to investigate the effects of cancerous growth on the metabolism of surrounding liver tissue. Maximum activities (capacity) of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, lactate dehydrogenase, succinate dehydrogenase, alkaline phosphatase, 5'-nucleotidase, xanthine oxidoreductase, purine nucleoside phosphorylase and adenosine triphosphatase have been determined. Two types of metastases were found, a small type surrounded by stroma and a larger type in direct contact with hepatocytes. Both types affected the adjacent tissue in a similar way suggesting that the interactions were not mediated by stroma. High capacity of the degradation pathway of extracellular purines released from dead cells of either tumours or host tissue was found in stroma and sinusoidal cells. Metastases induced both an increase in the number of Kupffer cells and proliferation of hepatocytes. The distribution pattern in the liver lobulus of most enzymes investigated did not change distinctly. However, activity of alkaline phosphatase, succinate dehydrogenase and phosphogluconate dehydrogenase was increased in hepatocytes directly surrounding metastases. These data imply that the overall metabolic zonation in liver lobuli is not dramatically disturbed by the presence of cancer cells despite the fact that various metabolic processes in liver cells are affected.
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PMID:Experimentally induced colon cancer metastases in rat liver increase the proliferation rate and capacity for purine catabolism in liver cells. 822 8

Freeze-substituted rat liver embedded in glycol methacrylate (GMA) has been used to demonstrate the activities of several enzymes. The following enzymes could be detected in GMA-sections by the indicated histochemical procedure(s): 5'-nucleotidase (lead salt, cerium-diaminobenzidine), alkaline phosphatase (indoxyl-tetrazolium salt), catalase (diaminobenzidine), acid phosphatase (diazonium salt), lactate dehydrogenase (tetrazolium salt) and glutamate dehydrogenase (tetrazolium salt). The activities of all these enzymes were dramatically decreased compared with the activities demonstrated in unfixed cryostat sections, with the exception of catalase. The activities of the following enzymes could not be detected in GMA-sections: glucose-6-phosphate dehydrogenase (tetrazolium salt), xanthine oxidoreductase (tetrazolium salt), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide) and glucose-6-phosphatase (cerium-diaminobenzidine). The possible role of restricted penetration of reagents into the resin was studied by measuring cytophotometrically the enzyme activities in GMA-sections of 3 and 6 microns in thickness. For all the enzymes that could be detected, the 6 microns:3 microns ratio varied from 1.4 to 2.7. An eventual retarded penetration of reagents into the resin was investigated by measuring cytophotometrically the amount of final reaction product during incubation for acid phosphatase and glutamate dehydrogenase activities. In both cases linear relationships without a lag phase were found for the specific enzyme activities with incubation time. Chemical denaturation of proteins or masking of active sites in proteins due to embedding in the resin monomer may be considered to be the main cause of decreased enzyme activities.
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PMID:Quantitative aspects of enzyme histochemistry on sections of freeze-substituted glycol methacrylate-embedded rat liver. 827 44

We studied the effect of allopurinol (ALL) on the activity of xanthine dehydrogenase (XDH), xanthine oxidase (XOX), superoxide dismutase (SOD), and catalase (CAT) in rat liver during ischemia followed by 60 min of reperfusion. We induced 60-min ischemia in the median and left lobes by clamping the hepatic artery and portal branches. The percentage XOX relative to total oxidase activity increased significantly in the control group, from 10% during the stabilization period to 18% after 60 min of reperfusion. The XDH activity decreased during reperfusion. Activity of both XDH and XOX was almost completely blocked by ALL. The activity of SOD and CAT did not differ significantly between the ALL group and controls after 60 min of reperfusion. ALL treatment did not affect liver injury parameters, as concentrations of lactate dehydrogenase (LDH) and alanine transferase (ALT) increased in plasma after ischemia, both in controls and in the ALL-treated group. We concluded that ischemia promotes conversion of XDH to XOX during reperfusion. XOX may not be the main source of free radical production, since intracellular scavengers (SOD and CAT) did not differ significantly between controls and the ALL-treated group, despite the fact that ALL blocked XOX activity completely.
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PMID:Normothermic liver ischemia in rats: xanthine oxidase is not the main source of oxygen free radicals. 827 74

Hypoxia and reoxygenation (H/R) generate oxygen free radicals that result in renal cell injury. We tested the roles of calcium and calmodulin in mediating xanthine oxidase-derived oxygen free radical production during H/R. Lowering extracellular Ca2+ attenuated lethal cell injury. H/R increased superoxide radical production over basal levels, whereas removing extracellular Ca2+ before hypoxia decreased superoxide radical production to basal levels. Pretreatment with either 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride or thapsigargin, to inhibit release or deplete stores of intracellular Ca2+, did not affect injury following H/R. Ionomycin increased lactate dehydrogenase release during H/R but did not increase superoxide radical to levels greater than that observed for H/R alone. The calmodulin inhibitors trifluoperazine, calmidazolium, or N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide decreased cell injury to varying degrees. Trifluoperazine also decreased superoxide radical production during H/R and was shown to inhibit the conversion of xanthine dehydrogenase to xanthine oxidase. Cell injury and superoxide radical production correlated with cytosolic free Ca2+ during H/R as determined with the Ca(2+)-sensitive fluoroprobe indo 1. Cytosolic free Ca2+ increased slightly during hypoxia and showed a dramatic increase as soon as cells were reoxygenated. Cells incubated in a Ca(2+)-free medium actually showed a small decrease in intracellular Ca2+ despite H/R. In summary, Ca2+ derived from extracellular sources promoted superoxide radical production and renal cell injury by a calmodulin-dependent conversion of xanthine dehydrogenase to xanthine oxidase, a major source of oxygen free radicals during H/R.
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PMID:Calcium and free radicals in hypoxia/reoxygenation injury of renal epithelial cells. 830 79

The purpose of the present study was to investigate whether local prevention of luminal superoxide-mediated biological damage in the rat jejunal mucosa could be achieved by use of cationized superoxide dismutase (SOD). Mucosal damage was induced in a closed circulating intestinal loop of the rat either by a mixture of xanthine and xanthine oxidase or by a mixture of xanthine, xanthine oxidase, and chelated ferrous sulfate. Thus, superoxide radicals or hydroxyl (OH.) radicals were induced. The mucosal activity of intracellular lactate dehydrogenase and the levels of cellular potassium ions were used to quantitatively characterize the tissue damage. SOD was cationized by reaction with N,N'-dimethyl-1,3-propanediamine to yield a soluble product or with polyhistidine to yield an insoluble product. The cationization yield and the activity of the modified enzymes were assessed, and the ability of the cationized enzymes to protect the rat jejunal mucosa against oxidative stress was studied. It was found that cationized SOD provided significant protection against mucosal damage induced by OH. radicals. The findings indicate the potential role of cationized enzymes in the local protection of the intestinal epithelium against pathological processes associated with oxidative stress.
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PMID:Protection of the rat jejunal mucosa against oxidative injury by cationized superoxide dismutase. 830 14

Allopurinol is a potent xanthine oxidase inhibitor that has been administered to animals to protect tissues from oxidant injury. We hypothesized that allopurinol may protect against oxidant injury by inhibiting the inflammatory response. Male Sprague-Dawley rats were injected daily with vehicle or allopurinol and compared with noninjected controls. Animals were exposed to room air or 90% oxygen for 14 days. At the end of the exposure period, all animals were lavaged and bronchoalveolar lavage fluid (BALF) was examined for cell counts, lactate dehydrogenase (LDH), and protein. BALF neutrophils were significantly increased in oxygen-exposed noninjected controls (33 +/- 7 x 10(3)/mm3) and also in the vehicle-inoculated oxygen-exposed animals (43 +/- 6 x 10(3)/mm3). Allopurinol treatment resulted in a decrease in the neutrophilic alveolar response in oxygen-exposed animals (5.3 +/- 4 x 10(3)/mm3, P < 0.001). These data reveal that oxygen exposure produces a neutrophilic alveolar response that is attenuated by allopurinol treatment. BALF protein and LDH were significantly increased in all inoculated and noninoculated oxygen-exposed animals compared with air-exposed animals. Therefore, allopurinol decreases the neutrophilic alveolar response produced by a hyperoxic exposure in the rat but does not decrease lung injury as assessed by alveolar LDH and protein release.
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PMID:Allopurinol inhibition of neutrophilic alveolar response during hyperoxia. 837 86

In this article the spontaneous chemiluminescence and the steady-state concentration of hydrogen peroxide were determined in rat liver as indicators of oxidative stress in the tissue. Hydroperoxide-initiated chemiluminescence and the activity of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) were also measured to evaluate antioxidant defenses and serum activity of lactate dehydrogenase and aspartate aminotransferase. Mitochondrial morphology and mitochondrial respiratory control ratio were measured as indicators of cell and mitochondrial damage. Xanthine dehydrogenase and xanthine oxidase activities were determined as a possible source of oxyradicals. No significant changes were observed after 10 or 30 min of vena cava occlusion in any of the measured parameters. In contrast, 10 min of occlusion followed by 10 min of reperfusion increased chemiluminescence (from 18 +/- 3 to 32 +/- 5 cps/cm2), hydrogen peroxide (from 0.10 +/- 0.01 to 0.17 +/- 0.01 mumol/L), lactate dehydrogenase (from 80 +/- 2 to 330 +/- 30 U/L), and aspartate aminotransferase (from 42 +/- 2 to 100 +/- 10 U/L). Liver reperfusion was also associated with mitochondrial swelling and decreased mitochondrial respiratory control (from 5.6 +/- 0.3 to 2.6 +/- 0.1). The activity of the antioxidant enzymes and xanthine oxidase was instead without change. After 30 min of vena cava occlusion and 10 min of reperfusion a more marked increase in chemiluminescence (37 +/- 5 cps/cm2), hydrogen peroxide (0.30 +/- 0.01 mumol/L), lactate dehydrogenase (730 +/- 10 U/L) and aspartate aminotransferase (140 +/- 10 U/L) was observed. No further changes were found in either mitochondrial morphology or respiratory control (2.4 +/- 0.1) in isolated mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oxidative stress produced by suprahepatic occlusion and reperfusion. 840 64

We studied the toxicity of free radicals to human mesothelial cells in vitro and to the peritoneal membrane of rats during peritoneal dialysis. Free radicals cause damage to mesothelial cells as measured by release of cytosolic markers such as 86Rb and lactate dehydrogenase. Vitamin E neutralized the toxic effect of free radicals in vitro. Human mesothelial cells exposed over 6 h to a mixture of essential and nonessential amino acids in medium are more vulnerable to the cytotoxic effect of free radicals than control cells exposed to medium alone. Cells exposed previously to glucose or glycerol are less vulnerable than controls. In rats free radicals generated intraperitoneally by a xanthine-xanthine oxidase system induce changes in peritoneal permeability similar to those observed during peritonitis: loss of ultrafiltration, increased glucose absorption from the dialysate and augmented transperitoneal loss of albumin. In addition lipids in the peritoneum became peroxidated. The addition of vitamin E to the peritoneal fluid with xanthine-xanthine oxidase prevents peroxidation of lipids and the subsequent loss of ultrafiltration. Our results show that free radicals may exert a potentially toxic effect on the peritoneal membrane during peritonitis. In such circumstances the addition of free radical scavenger to the dialysis fluid may preserve intact structure and function of peritoneum.
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PMID:Toxicity of free radicals to mesothelial cells and peritoneal membrane. 841 93

In the present investigation alterations in the free radical generating and scavenging enzymes in platelets, neutrophils (PMNLs), heart and lung homogenates following rat pulmonary thromboembolism have been studied. Thrombosis was induced by intravenous infusion of collagen and adrenaline. Levels of malonaldehyde (MDA) were elevated in the PMNLs after thrombosis. Activities of superoxide dismutase (SOD) and catalase (CAT) were found to increase in platelets and PMNLs respectively. However, there was no significant alteration in the lactate dehydrogenase (LDH), lysozyme (LYS), ratio of xanthine oxidase to dehydrogenase (XO/XH) and PMNLs O2- generation before and after thrombosis. Migration of PMNLs following thrombosis was indicated by increased activity of myeloperoxidase (MPO) in the heart. In addition, pretreatment with allopurinol, a xanthine oxidase inhibitor and indomethacin, a cyclooxygenase inhibitor offered protection against thromboembolism induced death/paralysis. Results suggest the involvement of free radicals in thrombosis.
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PMID:Free radical scavenging mechanisms during pulmonary thromboembolism in rats. 846 69

The effect of storage of unfixed cryostat sections from rat liver for 4 h, 24 h, 3 days and 7 days at -25 degrees C was studied on the activities of lactate dehydrogenase, glucose-6-phosphate dehydrogenase, xanthine oxidoreductase, glutamate dehydrogenase, succinate dehydrogenase (all demonstrated with tetrazolium salt procedures), glucose-6-phosphatase (cerium-diaminobenzidine method), 5'-nucleotidase (lead salt method), dipeptidyl peptidase II, acid phosphatase (both simultaneous azo coupling methods), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide procedure) and catalase (diaminobenzidine method). The effect of drying of the cryostat sections at room temperature for 5 and 60 min was investigated as well. The enzyme activities were quantified by cytophotometric measurements of test and control reactions. The test minus control reaction was taken as a measure for specific enzyme activity. It was found that the activities of all the enzymes investigated, with one exception, were affected neither by storage of the cryostat sections at -25 degrees C for up to 7 days, nor by drying of the sections at room temperature for up to 60 min. The exception was xanthine oxidoreductase, whose activity was reduced by 20% after 5 min drying of sections or after 4 h storage. Therefore, only incubations for xanthine oxidoreductase activity have to be performed immediately after cutting cryostat sections, whereas for the other enzymes a considerable margin appears to exist.
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PMID:The effects of storage on the retention of enzyme activity in cryostat sections. A quantitative histochemical study on rat liver. 846 85


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