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)

Reactive O2 species appear to be generated both during hypoxia and at reoxygenation, but it has not been established whether these species interact with heart tissue and cause injury. Oxidative changes were evaluated in isolated rat heart perfused with Krebs-Henseleit medium containing 10 mM glucose and 2.5 mM calcium. After 5-10 min hypoxia, tissue glutathione (GSH) decreased while glutathione disulfide (GSSG), protein carbonyls, and thiobarbituric acid reactive substances (TBARS) increased compared with controls. Similarly, sarcolemmal and sarcoplasmic reticular Ca-ATPase activity (an enzyme susceptible to oxidative inactivation) decreased in response to 10 min hypoxia. These changes were more pronounced after 60 min of hypoxia when protein-GSH mixed disulfides were also increased. There were no further oxidative changes after 4 min reoxygenation when the release of lactate dehydrogenase (LDH) was maximal. Myocardial protein thiol and alpha-tocopherol contents were not significantly changed by either hypoxia or reoxygenation. Mitochondria also exhibited oxidative changes but with more pronounced increases in GSSG and mixed disulfides. There was no change in GSH or GSSG efflux into the coronary effluent during hypoxia, although, in parallel with LDH release, both increased after reoxygenation. Diamide (200 microM), t-butylhydroperoxide (20 microM), or purine (2.3 mM) + xanthine oxidase (0.01 U/ml) were infused for 10 min. Except for large diamide-induced changes in protein thiols and mixed disulfides, the magnitude of the changes produced by these oxidants was similar to those produced by hypoxia. These data show that changes consistent with oxidative processes occur in whole heart and mitochondria in response to hypoxia. The absence of marked signs of oxidation at reoxygenation suggest that enzyme release at this time is unrelated to oxidative stress.
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PMID:Oxidative changes in hypoxic rat heart tissue. 203 61

The effects of oxidant stress (xanthine oxidase plus hypoxanthine or photoactivation of rose bengal) on the Na(+)-Ca(2+)-exchange current were studied in guinea pig ventricular myocytes with the use of voltage-clamp techniques. Oxidant stress depressed both the Ni(2+)-sensitive and extracellular calcium concentration ([Ca2+]o)-activated current in a time-dependent manner (e.g., xanthine oxidase plus hypoxanthine inhibited the Ni(2+)-sensitive current at +60 mV from 6.81 +/- 3.24 to 5.54 +/- 0.48 pA/pF; n = 6; P < 0.05). This effect was independent of the [Ca2+] of the pipette solution. Diamide, an alkylating agent that modifies protein sulfhydryl groups, also decreased the Ni(2+)-sensitive current (at + 60 mV: from 5.76 +/- 1.55 to 3.43 +/- 0.99 pA/pF; n = 6; P < 0.05). The stoichiometry (n) and partition coefficient (gamma) of the electrogenic Na(+)-Ca(2+)-exchange current seemed unchanged. Our results suggest that oxidant stress causes a direct or indirect sulfhydryl group-mediated decrease of the Na(+)-Ca2+ exchanger.
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PMID:Oxidant stress inhibits Na-Ca-exchange current in cardiac myocytes: mediation by sulfhydryl groups? 816 Aug 39

Time courses of total (GSH-t), disulfide (GSSG), and mixed disulfide (PSSG) forms of glutathione were studied in chicken blood submitted to oxidative stress induced by diamide or by the reactive oxygen species (ROS)-producing system xanthine/xanthine oxidase (X/XO). Diamide-treated blood induced an immediate increase in GSSG and PSSG, while X/XO produced a slow and sustained stress with increased values of GSSG and PSSG only after 30 and/or 60 min of incubation. Both total protein S-thiolation (mixed disulfide with glutathione) and dethiolation and hemoglobin A S-thiolation and dethiolation were clearly observed. Hemoglobin A (Hb A) was the major S-thiolated protein. We further characterized chicken Hb S-thiolation through the reaction of Hb with GSSG or the GSH/GSSG redox couple. Methemoglobin levels did not change with diamide or with X/XO treatment. Present results suggest that the most reactive cysteine pair of Hb A, the major chicken Hb, might function as an antioxidant under in vivo oxidative stress conditions.
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PMID:Oxidative stress causes intracellular reversible S-thiolation of chicken hemoglobin under diamide and xanthine oxidase treatment. 978 42