Nitric oxide dependent and independent effects of in vitro incubation or endotoxin on vascular reactivity in rat aorta

Mark Wylam, Andrea P. Metkus, Jason G. Umans

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

We sought to delineate contributions of nitric oxide (NO) and other mechanisms to impairment of contraction and endothelium-dependent relaxation following prolonged in vitro incubation, endotoxin and interleukin-1 exposure in isolated rat aorta. Responses from freshly-dissected (control) rings ±endothelium were compared with those from rings incubated in sterile, antibiotic containing medium ± E. Coli endotoxin (LPS, 100 μg/ml) ± interleukin-1 (IL-1, 40 ng/ml) at 37°C for 20-24 h. In some experiments, medium included dexamethasone (DEX, 1 μg/ml), cycloheximide (10 μg/ml), or NG-nitro-L-arginine (NNLA, 10-4M). After incubation, medium nitrite was measured. Incubation alone, without addition of inflammatory mediators, impaired contraction in an agonist-specific manner, by both NO-dependent and NO-independent mechanisms. Either LPS or IL-1 diminished contraction further, in a similarly heterogeneous manner. For example, contractions were changed in LPS-incubated endothelium-intact rings (vs. fresh controls) by -85%, +115%, -15%, -96%, and -37% for phenylephrine (PE), serotonin, prostaglandin F, angiotensin II, and U46619, respectively. NO synthase inhibition with NNLA either following, or during LPS incubation only partially normalized subsequent PE contractions, an effect which was smaller than that of DEX. Nitrite accumulation was inversely proportional to PE response, even though NO was not the sole mediator of LPS-impaired contraction. LPS and IL-1 nearly abolished ACh-induced relaxation, which was only mildly impaired by incubation alone. We conclude that prolonged incubation impaired vasoconstriction via both NO synthase induction and NO-independent mechanisms. LPS or IL-1 incubation impaired vasoconstriction further, primarily by NO-independent mechanisms. Moreover, vasoconstrictor responses following LPS varied with the agonist's ability to modulate endothelial NO release. These results are in accord with the failure of NO synthase inhibition to fully restore systemic vascular resistance indices in experimental endotoxemia or in hyperdynamic septic patients.

Original languageEnglish (US)
Pages (from-to)455-467
Number of pages13
JournalLife Sciences
Volume69
Issue number4
DOIs
StatePublished - Jun 15 2001

Fingerprint

Endotoxins
Blood Vessels
Aorta
Rats
Interleukin-1
Nitric Oxide
Phenylephrine
Nitric Oxide Synthase
Endothelium
Nitrites
Vasoconstriction
15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
Endotoxemia
Dinoprost
Nitroarginine
Vasoconstrictor Agents
Cycloheximide
In Vitro Techniques
Angiotensin II
Vascular Resistance

Keywords

  • Endothelium
  • Endotoxin
  • Nitric oxide
  • Vascular
  • Vasoconstriction
  • Vasorelaxation

ASJC Scopus subject areas

  • Pharmacology

Cite this

Nitric oxide dependent and independent effects of in vitro incubation or endotoxin on vascular reactivity in rat aorta. / Wylam, Mark; Metkus, Andrea P.; Umans, Jason G.

In: Life Sciences, Vol. 69, No. 4, 15.06.2001, p. 455-467.

Research output: Contribution to journalArticle

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