Role of endothelium/nitric oxide in vascular response to flavonoids and epicatechin.
OBJECTIVE
To examine the role of endothelium in the vascular responses to flavonoids, baicalein, baicalin, cardamonin, alpinetin, and to purified jasmine green tea (-)epicatechin in the isolated rate mesenteric artery rings.


METHODS
The isometric contraction was measured by Grass force-displacement transducers.


RESULTS
Both baicalein and baicalin enhanced the phenylephrine-induced contractile response in the endothelium-intact rings. This enhancement was abolished by pretreatment with the nitric oxide inhibitor NG-nitro-L-arginine or in the absence of the endothelium. Both flavonoids also inhibited the acetylcholine-induced endothelial nitric oxide-dependent relaxation. In contrast, cardamonin, alpinetin or (-)epicatechin induced both endothelium-dependent and -independent relaxation. NG-nitro-L-arginine meyhyl ester or endothelium denudation attenuated the endothelium-dependent relaxation to the same extent.


CONCLUSIONS
Baicalein and baicalin enhanced the phenylephrine-induced contraction most likely through inhibiting production or/and release of endothelial nitric oxide. Whilst, cardamonin-, alpinetin- or (-)epicatechin-induced endothelium-dependent relaxation is primarily mediated through endothelial nitric oxide.
Huang
Y
Y
Departments of Physiology and Biochemistry, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China. yu-huang@cuhk.edu.hk
Yao
X Q
XQ
Tsang
S Y
SY
Lau
C W
CW
Chen
Z Y
ZY
D000818:Animals; D002392:Catechin / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000502:physiology*; D044950:Flavanones; D005419:Flavonoids / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects*; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine; D051381:Rats; D017207:Rats, Sprague-Dawley
D044950:Flavanones; D005419:Flavonoids; D019335:Nitroarginine; D009569:Nitric Oxide; C038044:baicalin; C006680:baicalein; D002392:Catechin