title: Unaltered vasoconstrictor responsiveness after iNOS inhibition in lungs from chronically hypoxic rats.
abstract: Previous studies suggest that inducible (i) nitric oxide synthase (NOS) expression within the pulmonary vasculature is increased in rats with chronic hypoxia (CH)-induced pulmonary hypertension. We therefore hypothesized that enhanced iNOS expression associated with CH causes attenuated pulmonary vasoconstrictor responsiveness. To test this hypothesis, we examined the effect of selective iNOS blockade with L-N6-(1-iminoethyl)lysine dihydrochloride (L-NIL) and nonselective NOS inhibition with Nomega-nitro-L-arginine (L-NNA) on vasoconstrictor responses to U-46619 in isolated saline-perfused lungs from both control and CH (4 wk at 380 mmHg) rats. We additionally measured pulmonary hemodynamic responses to L-NIL in conscious CH rats (fraction of inspired O2 = 0.12). Finally, iNOS mRNA levels were assessed in lungs from each group of rats using ribonuclease protection assays. Despite a significant increase in iNOS mRNA expression after exposure to CH, responses to U-46619 were unaltered by L-NIL but augmented by L-NNA in lungs from both control and CH rats. Pulmonary hemodynamics were similarly unaltered by L-NIL in conscious CH rats. We conclude that iNOS does not modulate pulmonary vasoconstrictor responsiveness after long-term hypoxic exposure.
authors.affiliation: Departments of Cell Biology and Physiology, and Pediatrics, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: Resta
authors.forename: T L
authors.initials: TL
authors.lastname: O'Donaughy
authors.forename: S
authors.initials: S
authors.lastname: Earley
authors.forename: L G
authors.initials: LG
authors.lastname: Chicoine
authors.forename: B R
authors.initials: BR
authors.lastname: Walker
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D002908:Chronic Disease; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D000860:Hypoxia / Q000201:enzymology* / Q000503:physiopathology*; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D008168:Lung / Q000201:enzymology* / Q000503:physiopathology*; D008239:Lysine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D019335:Nitroarginine / Q000494:pharmacology; D011652:Pulmonary Circulation / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; C090663:N(6)-(1-iminoethyl)lysine; D014662:Vasoconstrictor Agents; D019335:Nitroarginine; D009569:Nitric Oxide; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D008239:Lysine