title: Mechanism of vasorelaxation induced by eupatorin in the rats aortic ring.
abstract: Previous studies demonstrated that eupatorin content in Orthosiphon stamineus fractions correlated with their vasorelaxation activity. Even with previous studies, there is still very little information on the vasorelaxation effect of eupatorin, and not many scientific studies had been carried out. Therefore, the present study was designed to investigate the vasorelaxation activity and mechanism of action of eupatorin. The vasorelaxation activity and the underlying mechanisms of eupatorin was evaluated on thoracic aortic rings isolated from Sprague Dawley rats. Eupatorin caused the relaxation of aortic rings pre-contracted with phenylephrine with and without endothelium (pD2=6.66±0.13, EMAX=99.72±6.39%; pD2=6.10±0.22, EMAX=65.78±8.01%), and also the relaxation of endothelium-intact aortic rings pre-contracted with potassium chloride (pD2=6.20±0.30, EMAX=71.89±12.25%). In the presence of Nω-nitro-l-arginine methyl ester (pD2<4.60, EMAX=24.91±6.39%), methylene blue (pD2=6.05±0.38, EMAX=66.79±9.69%), ODQ (pD25.84±0.32, EMAX=60.47±9.6%), indomethacin (pD2=6.27±0.21, EMAX=76.03±9.45%), tetraethylammonium (pD2=6.09±0.35, EMAX=69.35±11.31%), 4-aminopyridine (pD2=6.34±0.12, EMAX=76±6.1%), barium chloride (pD2=6.47±0.14, EMAX=79.61±10.02%), atropine (pD2=6.36±0.29, EMAX=86.47±12.95%) and propranolol (pD2=6.49±0.26, EMAX=83.2±12.01%), relaxation stimulated by eupatorin was significantly reduced. Eupatorin was also found to be active in reducing Ca(2+) release from sarcoplasmic reticulum and in blocking calcium channels. The present study demonstrates the vasorelaxation effect of eupatorin involving NO/sGC/cGMP and indomethacin pathways, calcium and potassium channels, and muscarinic and beta-adrenergic receptors.
authors.affiliation: College of Pharmacy, Fujian University of Traditional Chinese Medicine, 1 Qiuyang Road, Shangjie, Minhou, Fuzhou 350122, Fujian, China; School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia.
authors.forename: Mun Fei
authors.initials: MF
authors.lastname: Yam
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia. Electronic address: weazley90@hotmail.com.
authors.forename: Chu Shan
authors.initials: CS
authors.lastname: Tan
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia.
authors.forename: Mariam
authors.initials: M
authors.lastname: Ahmad
authors.affiliation: College of Pharmacy, Fujian University of Traditional Chinese Medicine, 1 Qiuyang Road, Shangjie, Minhou, Fuzhou 350122, Fujian, China. Electronic address: 1554850002@qq.com.
authors.forename: Ruan
authors.initials: R
authors.lastname: Shibao
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000502:physiology*; D002122:Calcium Chloride / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D005419:Flavonoids; C103110:eupatorin; D002122:Calcium Chloride
keywords: Calcium and potassium channels; Eupatorin; Muscarinic and beta-adrenergic receptors; NO/sGC/cGMP pathway