Progressive dysfunction of nitric oxide synthase in a lamb model of chronically increased pulmonary blood flow: a role for oxidative stress

Am J Physiol Lung Cell Mol Physiol. 2008 Nov;295(5):L756-66. doi: 10.1152/ajplung.00146.2007. Epub 2008 Aug 29.

Abstract

Cardiac defects associated with increased pulmonary blood flow result in pulmonary vascular dysfunction that may relate to a decrease in bioavailable nitric oxide (NO). An 8-mm graft (shunt) was placed between the aorta and pulmonary artery in 30 late gestation fetal lambs; 27 fetal lambs underwent a sham procedure. Hemodynamic responses to ACh (1 microg/kg) and inhaled NO (40 ppm) were assessed at 2, 4, and 8 wk of age. Lung tissue nitric oxide synthase (NOS) activity, endothelial NOS (eNOS), neuronal NOS (nNOS), inducible NOS (iNOS), and heat shock protein 90 (HSP90), lung tissue and plasma nitrate and nitrite (NO(x)), and lung tissue superoxide anion and nitrated eNOS levels were determined. In shunted lambs, ACh decreased pulmonary artery pressure at 2 wk (P < 0.05) but not at 4 and 8 wk. Inhaled NO decreased pulmonary artery pressure at each age (P < 0.05). In control lambs, ACh and inhaled NO decreased pulmonary artery pressure at each age (P < 0.05). Total NOS activity did not change from 2 to 8 wk in control lambs but increased in shunted lambs (ANOVA, P < 0.05). Conversely, NO(x) levels relative to NOS activity were lower in shunted lambs than controls at 4 and 8 wk (P < 0.05). eNOS protein levels were greater in shunted lambs than controls at 4 wk of age (P < 0.05). Superoxide levels increased from 2 to 8 wk in control and shunted lambs (ANOVA, P < 0.05) and were greater in shunted lambs than controls at all ages (P < 0.05). Nitrated eNOS levels were greater in shunted lambs than controls at each age (P < 0.05). We conclude that increased pulmonary blood flow results in progressive impairment of basal and agonist-induced NOS function, in part secondary to oxidative stress that decreases bioavailable NO.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Blood Pressure / drug effects
  • Chronic Disease
  • Disease Models, Animal
  • Female
  • HSP90 Heat-Shock Proteins / metabolism
  • Lung / enzymology
  • Lung / pathology
  • Lung / physiopathology
  • Nitrates / blood
  • Nitric Oxide Synthase / metabolism*
  • Nitric Oxide Synthase Type III / metabolism
  • Nitrites / blood
  • Oxidative Stress* / drug effects
  • Pulmonary Artery / drug effects
  • Pulmonary Artery / enzymology
  • Pulmonary Artery / pathology
  • Pulmonary Artery / physiopathology
  • Pulmonary Circulation / drug effects
  • Pulmonary Circulation / physiology*
  • Sheep
  • Superoxides / metabolism

Substances

  • HSP90 Heat-Shock Proteins
  • Nitrates
  • Nitrites
  • Superoxides
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type III
  • Acetylcholine