Xanthine oxidase (XO0 derived from xanthine dehydrogenase (XD) during ischemia plays important roles in tissue damage by generating superoxide radicals. In the present study, we examined in vivo regulations of XD-XO activities of various organs
by
environmental oxygen tesion. Mice were exposed to 100% oxygen for 3, 10, or 30 h, or 7% oxygen (73% nitrogen) for 4th. XD-XO activities of liver, kidney, lung and brain were measured. The enzyme activities in both liver and kidney were markedly
increased by the treatment with 100% oxygen. In the liver the enhanced activity was sustained until 30 h, while the elevated renal activity was found only in the mouse treated for 10 h. XD-XO activities were decreased in lung and brain by the
treatment
with 100% oxygen. When mice were exposed to 7% oxygen, XD-XO activity was markedly decreased in lung and brain, while the activities in liver and kidney ere not significantly changed. These results indicate that XD-XO can be regulated by the
environmental oxygen tension. And the regulation is organ-specific.
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