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Updated: Sep 25, 2026
Alternative Methods for the Detection of Superoxide Anion Generation in Platelets
Published on: March 29, 2024
Electron spin resonance detection of hydrogen peroxide as an endothelium-derived hyperpolarizing factor in porcine
Tetsuya Matoba1, Hiroaki Shimokawa, Keiko Morikawa
1Department of Cardiovascular Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
Objective:
Endothelium-derived hyperpolarizing factor (EDHF) plays an important role in modulating vascular tone, especially in microvessels, although its nature has yet to be elucidated. This study was designed to examine whether hydrogen peroxide (H2O2) is an EDHF in porcine coronary microvessels with use of an electron spin resonance (ESR) method to directly detect H2O2 production from the endothelium.
Methods And Results:
Isometric tension and membrane-potential recordings demonstrated that bradykinin and substance P caused EDHF-mediated relaxations and hyperpolarizations of porcine coronary microvessels in the presence of indomethacin and Nomega-nitro-L-arginine. The contribution of H2O2 to the EDHF-mediated responses was demonstrated by the inhibitory effect of catalase and by the relaxing and hyperpolarizing effects of exogenous H2O2. Endothelial production of H2O2 was quantified in bradykinin- or substance P-stimulated intact blood vessels by ESR spectroscopy. Tiron, a superoxide scavenger that facilitates H2O2 formation, enhanced bradykinin-induced production of H2O2, as well as the EDHF-mediated relaxations and hyperpolarizations. By contrast, cytochrome P-450 inhibitors (sulfaphenazole or 17-octadecynoic acid) or a gap junction inhibitor (18alpha-glycyrrhetinic acid) failed to inhibit the EDHF-mediated relaxations. Involvement of endothelium-derived K+ was not evident in experiments with ouabain plus Ba2+ or exogenous K+.
Conclusions:
These results provide ESR evidence that H2O2 is an EDHF in porcine coronary microvessels.
