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

Am J Physiol Heart Circ Physiol. 2009 Feb;296(2):H524-33. doi: 10.1152/ajpheart.00543.2008. Epub 2008 Dec 12.


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% O(2) 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% O(2) 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.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / pharmacology
  • Allopurinol / pharmacology*
  • Animals
  • Blood Pressure / drug effects
  • Cardiac Output / drug effects
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Enzyme Inhibitors / pharmacology*
  • Hydrazines / pharmacology
  • Hypoxia / enzymology
  • Hypoxia / physiopathology
  • Injections, Intravenous
  • Male
  • NG-Nitroarginine Methyl Ester / pharmacology
  • Nitric Oxide / metabolism*
  • Nitric Oxide Donors / pharmacology
  • Nitric Oxide Synthase / antagonists & inhibitors
  • Nitric Oxide Synthase / metabolism
  • Nitroprusside / pharmacology
  • Oxypurinol / pharmacology
  • Pulmonary Artery / drug effects*
  • Pulmonary Artery / enzymology
  • Rats
  • Rats, Sprague-Dawley
  • Sodium Nitrite / administration & dosage
  • Sodium Nitrite / pharmacology*
  • Time Factors
  • Vasoconstrictor Agents / pharmacology
  • Vasodilation / drug effects*
  • Vasodilator Agents / administration & dosage
  • Vasodilator Agents / pharmacology*
  • Xanthine Oxidase / antagonists & inhibitors*
  • Xanthine Oxidase / metabolism


  • Enzyme Inhibitors
  • Hydrazines
  • Nitric Oxide Donors
  • Vasoconstrictor Agents
  • Vasodilator Agents
  • Nitroprusside
  • Nitric Oxide
  • Allopurinol
  • 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
  • 1,1-diethyl-2-hydroxy-2-nitrosohydrazine
  • Nitric Oxide Synthase
  • Xanthine Oxidase
  • Oxypurinol
  • Sodium Nitrite
  • NG-Nitroarginine Methyl Ester