title: Role of endothelium/nitric oxide in vascular response to flavonoids and epicatechin.
abstract: 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.
authors.affiliation: Departments of Physiology and Biochemistry, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China. yu-huang@cuhk.edu.hk
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
authors.forename: X Q
authors.initials: XQ
authors.lastname: Yao
authors.forename: S Y
authors.initials: SY
authors.lastname: Tsang
authors.forename: C W
authors.initials: CW
authors.lastname: Lau
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Chen
mesh_terms: 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
chemical_list: D044950:Flavanones; D005419:Flavonoids; D019335:Nitroarginine; D009569:Nitric Oxide; C038044:baicalin; C006680:baicalein; D002392:Catechin