Role of xanthine oxidase and its inhibitor in hypoxia: reoxygenation injury.
OBJECTIVE
This article reviews the biochemistry and function of xanthine dehydrogenase (XDH) and xanthine oxidase (XO) as well as their role in hypoxia-reoxygenation injury. Possible benefits of XO blockade are discussed.


METHODS
The available literature was reviewed.


RESULTS
It is evident that relatively high activities of XO are restricted to a few organs in man. Because positive effects of XO blockade with allopurinol have been reported even in organs containing relatively low activities of XO, two other possible favorable actions of allopurinol are mentioned. First it may act as an oxygen radical scavenger, and second, it may augment the adenine nucleotides and, hence, adenosine triphosphate concentration in the cell.


CONCLUSIONS
XDH and XO may play an important role in a series of pathophysiologic conditions. Their role in hypoxia-reoxygenation injury has been critically reviewed. However, care should be exercised in starting randomized trials to prevent hypoxia-reoxygenation injury with allopurinol, especially in newborn infants.


CONCLUSIONS
XDH and XO are released from the liver during hypoxic conditions, for instance, and consequently, they may reach a number of organs via the circulation.
Saugstad
O D
OD
Department of Pediatric Research, National Hospital, Oslo, Norway.
D000818:Animals; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D006801:Humans; D000860:Hypoxia / Q000188:drug therapy / Q000201:enzymology*; D010100:Oxygen / Q000009:adverse effects*; D014968:Xanthine Dehydrogenase / Q000037:antagonists & inhibitors* / Q000502:physiology*; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors* / Q000502:physiology*
D004791:Enzyme Inhibitors; D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase; D010100:Oxygen