RGD Reference Report - Hyperoxia and xanthine dehydrogenase/oxidase activities in rat lung and heart. - Rat Genome Database

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Hyperoxia and xanthine dehydrogenase/oxidase activities in rat lung and heart.

Authors: Elsayed, N M  Tierney, D F 
Citation: Elsayed NM and Tierney DF, Arch Biochem Biophys. 1989 Sep;273(2):281-6.
RGD ID: 13209004
Pubmed: PMID:2549869   (View Abstract at PubMed)

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.



RGD Manual Disease Annotations    Click to see Annotation Detail View

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
XDHHumanHyperoxic Lung Injury  ISOXdh (Rattus norvegicus) RGD 
XdhRatHyperoxic Lung Injury  IEP  RGD 
XdhMouseHyperoxic Lung Injury  ISOXdh (Rattus norvegicus) RGD 

Gene Ontology Annotations    Click to see Annotation Detail View

Molecular Function

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
XdhRat2 iron, 2 sulfur cluster binding  IDA  RGD 
XdhRatidentical protein binding  IPIXdh (Rattus norvegicus)homodimerizationRGD 

Objects Annotated

Genes (Rattus norvegicus)
Xdh  (xanthine dehydrogenase)

Genes (Mus musculus)
Xdh  (xanthine dehydrogenase)

Genes (Homo sapiens)
XDH  (xanthine dehydrogenase)


Additional Information