Regulation of intracellular xanthine oxidase by endothelial-derived nitric oxide

Claudia G. Cote, Feng Sheng Yu, Javier J. Zulueta, Robert J. Vosatka, Paul M. Hassoun

Research output: Contribution to journalArticlepeer-review


We have previously shown that nitric oxide (NO) donors, such as nitrosoglutathione, inhibit endothelial cell (EC) xanthine dehydrogenase (XD)/xanthine oxidase (XO) activity. The purpose of this study was to assess whether endothelial-derived NO plays any role in the regulation of intracellular XD/XO. We exposed rat pulmonary microvascular EC to L-arginine (precursor of NO) or inhibitors of nitric oxide synthase (NOS), i.e., N(G)- nitro-L-arginine methyl esther (L-NAME) and N(G)-nitro-L-arginine, in conditions of normoxia, hypoxia, and hypoxia followed by reoxygenation. Hypoxia alone caused a 1.9- and a 6.6-fold increase in XO and a 5-fold increase in XO + XD activities after 24 and 48 h of exposure, respectively. The combination of hypoxia and L-NAME (300 μM) treatment amounted at 48 h to a 10- and 7.5-fold increase in XO and XO + XD activities, respectively, compared with normoxic untreated cells. L-NAME also prevented the decline in XD/XO activity that occurred in untreated EC after hypoxia-reoxygenation. On the other hand, treatment with L-arginine caused a dose-dependent decrease in XD/XO activity in hypoxic EC compared with cells provided with L-arginine- free medium. In separate experiments, we assessed the role of L-arginine supplementation on the in vivo regulation of lung XD/XO by exposing male adult Sprague-Dawley rats for a period of 5 days to a hypoxic hypobaric atmosphere (0.5 atm). Exposure to hypoxia produced a significant increase in lung tissue XO activity and an increase in the ratio of XO to XD, L-Arginine supplementation in the drinking water prevented the increase in lung XO and the XO-to-XD ratio in hypoxic rats and caused a significant decrease in XO and XD in rats exposed to normoxia. In conclusion, this study suggests that endogenous NO has a significant role in the regulation of XD/XO both in vitro and in vivo. By inhibiting XD/XO activity, NO may have a modulating effect in conditions of hypoxia and hypoxia-reoxygenation, where this enzyme is thought to be important.

Original languageEnglish (US)
Pages (from-to)L869-L874
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Issue number5 15-5
StatePublished - Nov 1996
Externally publishedYes


  • L-arginine
  • N(G)-nitro-L-arginine methyl ester
  • hypoxia
  • nitric oxide synthase

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology


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