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This Article Full Text Full Text (PDF) All Versions of this Article: 296/2/H524    most recent 00543.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Casey, D. B. Articles by Kadowitz, P. J. Search for Related Content PubMed PubMed Citation Articles by Casey, D. B. Articles by Kadowitz, P. J.

Pulmonary vasodilator responses to sodium nitrite are mediated by an allopurinol-sensitive mechanism in the rat

¹Department of Pharmacology, Tulane University Health Science Center, and ²Department of Anesthesiology, Ochsner Clinic Foundation, New Orleans, LA

Submitted 22 May 2008 ; accepted in final form 10 December 2008

Recent studies show that pulmonary vasodilator responses to nitrite are enhanced by hypoxia. However, the mechanism by which nitrite is converted to vasoactive nitric oxide (NO) is uncertain. In the present study, intravenous injections of sodium nitrite decreased pulmonary and systemic arterial pressures and increased cardiac output. The decreases in pulmonary arterial pressure were enhanced when tone in the pulmonary vascular bed was increased with U-46619. Under elevated tone conditions, decreases in pulmonary and systemic arterial pressures in response to nitrite were attenuated by allopurinol in a dose that did not alter responses to the NO donors, sodium nitroprusside and diethylamine/NO, suggesting that xanthine oxidoreductase is the major enzyme-reducing nitrite to NO. Ventilation with a 10% O₂ gas mixture increased pulmonary arterial pressure, and the response to hypoxia was enhanced by N^G-nitro-L-arginine methyl ester and not altered by allopurinol. This suggests that NO formed by the endothelium and not from the reduction of plasma nitrite modulates the hypoxic pulmonary vasoconstrictor response. Although intravenous injections of sodium nitrite reversed pulmonary hypertensive responses to U-46619, hypoxia, and N^G-nitro-L-arginine methyl ester, the pulmonary vasodilator response to nitrite was not altered by ventilation with 10% O₂ when baseline pulmonary arterial pressure was increased to similar values in animals breathing room air or the hypoxic gas. These data provide evidence that xanthine oxidoreductase is the major enzyme-reducing nitrite to vasoactive NO, and that this mechanism is not modified by hypoxia.

nitric oxide; xanthine oxidoreductase; pulmonary hypertension; nitric oxide synthase

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