title: Involvement of endothelium/nitric oxide in vasorelaxation induced by purified green tea (-)epicatechin.
abstract: The present study investigated the involvement of endothelial nitric oxide in relaxation induced by purified green tea (-)epicatechin in rat isolated mesenteric arteries. (-)Epicatechin caused both endothelium-dependent and -independent relaxation. NG-Nitro-L-arginine methyl ester (L-NAME, 100 microM) and methylene blue (10 microM) significantly attenuated (-)epicatechin-induced relaxation in endothelium-intact tissues. L-Arginine (1 mM) partially antagonized the effect of L-NAME. (-)Epicatechin-induced relaxation was inhibited by Rp-guanosine 3',5'-cyclic monophosphothioate triethylamine. In contrast, indomethacin and glibenclamide had no effect. (-)Epicatechin (100 microM) significantly increased the tissue content of cyclic GMP and NG-nitro-L-arginine (100 microM) or removal of the endothelium abolished this increase. (-)Epicatechin (100 microM) induced an increase in intracellular Ca2+ levels in cultured human umbilical vein endothelial cells. Iberiotoxin at 100 nM attenuated (-)epicatechin-induced relaxation in endothelium-intact arteries and this effect was absent in the presence of 100 microM L-NAME. In summary, (-)epicatechin-induced endothelium-dependent relaxation is primarily mediated by nitric oxide and partially through nitric oxide-dependent activation of iberiotoxin-sensitive K+ channels. In addition, there may be a causal link between increased Ca2+ levels and nitric oxide release in response to (-)epicatechin.
authors.affiliation: Department of Physiology, Chinese University of Hong Kong, Faculty of Medicine, Shatin, Hong Kong. yu-huang@cuhk.edu.hk
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
authors.forename: N W
authors.initials: NW
authors.lastname: Chan
authors.forename: C W
authors.initials: CW
authors.lastname: Lau
authors.forename: X Q
authors.initials: XQ
authors.lastname: Yao
authors.forename: F L
authors.initials: FL
authors.lastname: Chan
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Chen
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000032:analysis; D002392:Catechin / Q000494:pharmacology*; D006152:Cyclic GMP / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010656:Phenylephrine; D051381:Rats; D017207:Rats, Sprague-Dawley; D013662:Tea; D014664:Vasodilation
chemical_list: D015220:Calcium Channels; D013662:Tea; D010656:Phenylephrine; D009569:Nitric Oxide; D002392:Catechin; D006152:Cyclic GMP