Regulation of xanthine dehydrogenase and xanthine oxidase activity by hypoxia.
The present study determined the effect of hypoxia on xanthine dehydrogenase ( XDH) and xanthine oxidase (XO) activity and gene and protein expression in cultured bovine aortic endothelial cells (BAEC). BAEC were exposed to hypoxia (3% O2) or anoxia (0% O2) for 24 or 48 h and to 24 h of hypoxia followed by 24 h of reoxygenation. Hypoxia- and anoxia-exposed BAEC demonstrated a greater than twofold increase in XDH/XO activity at 24 and 48 h compared with timed controls. Hypoxic cells that were subsequently reoxygenated in 21% O2 also demonstrated a similar increase in XDH/XO activity vs. timed controls. No differences were seen in mRNA levels at any time point. Similarly, no difference was noted in XDH/XO protein expression after hypoxic exposure, as determined by Western blot analysis. The increase in XDH/XO activity was not prevented by cyclohexamide, indicating that protein synthesis was not required. Thus the increased XDH/XO activity observed in response to hypoxia in the present study was due to posttranslational modulation of the enzyme.[1]References
- Regulation of xanthine dehydrogenase and xanthine oxidase activity by hypoxia. Poss, W.B., Huecksteadt, T.P., Panus, P.C., Freeman, B.A., Hoidal, J.R. Am. J. Physiol. (1996) [Pubmed]
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