(-)epicatechin induces and modulates endothelium-dependent relaxation in isolated rat mesenteric artery rings.
OBJECTIVE
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.


CONCLUSIONS
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.
Chen
Zhen-Yu
ZY
Department of Biochemistry, Chinese University of Hong Kong, China.
Yao
Xiao-Qiang
XQ
Chan
Franky Leung
FL
Lau
Chi-Wai
CW
Huang
Yu
Y
D000818:Animals; D002392:Catechin / Q000302:isolation & purification / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects*; D008751:Methylene Blue / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism; D013662:Tea / Q000737:chemistry*; D014664:Vasodilation / Q000187:drug effects*
D013662:Tea; D010656:Phenylephrine; D002392:Catechin; D019001:Nitric Oxide Synthase; D008751:Methylene Blue; D019331:NG-Nitroarginine Methyl Ester