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(-)epicatechin induces and modulates endothelium-dependent relaxation in isolated rat mesenteric artery rings
Zhen-Yu Chen1, Xiao-Qiang Yao, Franky Leung Chan
1Department of Biochemistry, Chinese University of Hong Kong, China.
Aim:
The present study was aimed to examine the role of endothelial nitric oxide in the relaxant response to green tea (-)epicatechin and its modulation of endothelium-mediated relaxation in the isolated rat mesenteric artery rings.
Methods:
Changes in the isometric tension were measured with Grass force-displacement transducers.
Results:
The (-)epicatechin-induced relaxation was largely dependent on the presence of intact endothelium and was reversed by NG-nitro-L-arginine methyl ester 10 micromol/L or methylene blue 10 micromol/L, the inhibitors of nitric oxide-mediated relaxation. L-Arginine at 1 mmol/L antagonized the effect of L-NAME or methylene blue. Pretreatment of endothelium-intact rings with (-)epicatechin 10 micromol/L enhanced the relaxation induced by endothelium-dependent vasodilator, acetylcholine, while this concentration did not influence the endothelium-independent relaxation induced by sodium nitroprusside in the endothelium-denuded artery rings.
Conclusion:
The results indicate that the endothelium-dependent vasodilation by (-)epicatechin is mainly mediated through nitric oxide and low concentration of (-)epicatechin augments endothelium-dependent vasorelaxation in the rat mesenteric arteries.