Oxygen radical-mediated reduction in basal and agonist-evoked no release in isolated rat heart

Nazareno Paolocci, Roberto Biondi, Marco Bettini, Chang Il Lee, Carlos O. Berlowitz, Ruggero Rossi, Yong Xia, Giuseppe Ambrosio, Antonio L'Abbate, David A. Kass, Jay L. Zweier

Research output: Contribution to journalArticlepeer-review

Abstract

Oxygen free radicals (OFR) play a primary role in ischemia - reperfusion-mediated vascular dysfunction and this is paralleled by a loss of endothelial nitric oxide synthase (eNOS) activity. The authors tested whether a direct exposure to OFR may affect vascular relaxation by altering nitric oxide (NO) release. Effects of electrolysis(EL)-generated OFR on basal and agonist-evoked NO release were monitored in isolated rat hearts by oxyhemoglobin assay. Electrolysis-induced changes were compared with those obtained after 30 min perfusion with NOS and cyclooxygenase (COX) inhibitors NG-nitro-L-arginine methyl ester (L-NAME. 100 μM) and indomethacin (INDO. 1 mM). Electrolysis-generated hydroxyl radical (·OH) formed by ·O2- and H2O2 via the Fenton reaction as revealed by Electron Paramagnetic Resonance (EPR). After EL, basal NO release declined by 60% and coronary perfusion pressure (CPP) increased by ≅70%. L-NAME/INDO perfusion similarly lowered NO release (-63%) but increased CPP less than EL (56 ± 3%; P<0.03 ν post-EL). In presence of excess substrates and cofactors eNOS activity was not affected by EL. Both acetylcholine (ACh; 1 μM) and bradykinin (BK; 10 nM) had minimal effect in reversing EL-induced vasocontriction, whereas both partially reversed L-NAME/INDO-mediated constriction. Sodium nitroprusside (SNP. 1 μM) completely reversed L-NAME/INDO constriction and partly countered that after EL (-38 ± 2.5. P<0.001). Acetylcholine-evoked NO release was nearly abolished by both treatments whereas BK still elicited partial NO release after eNOS/cyclooxygenase inhibition (P<0.001) but not after EL. In conclusion. OFR severely impair NO-mediated coronary vasorelaxation affecting both basal and agonist-evoked NO release but not eNOS activity. However, EL also significantly blunts NOS/COX-independent vasodilation suggesting alteration of other vasodilatative pathways.

Original languageEnglish (US)
Pages (from-to)671-679
Number of pages9
JournalJournal of Molecular and Cellular Cardiology
Volume33
Issue number4
DOIs
StatePublished - 2001

Keywords

  • Acetylcholine
  • Bradykinin
  • Coronary flow
  • Electrolysis
  • Endothelial nitric oxide synthase
  • Nitric oxide
  • Oxygen free radicals
  • Sodium nitroprusside

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

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