title: Endothelium-independent vasorelaxation effects of Sigesbeckia glabrescens (Makino) Makino on isolated rat thoracic aorta.
abstract: The present study aimed to investigate the vasorelaxant effect of the methanol extract of Sigesbeckia glabrescens (Makino) Makino (MESG) on rat aortic rings and mechanism of action. MESG inhibited both noradrenaline bitartrate (NA)- and potassium chloride (KCl)-induced contraction of endothelium-intact aortic rings in a concentration-dependent manner. Removal of the endothelium did not influence the effect of MESG on NA-precontracted aortic rings. Pretreatment with MESG (250 µg/mL) inhibited calcium chloride-induced vasocontraction of NA- or KCl-precontracted endothelium-denuded aortic rings. It also relaxed phorbol-12-myristate-13-acetate-induced contraction of aortic rings in a concentration-dependent manner. In addition, Bay K8644 (an L-type calcium channel opener) vasocontracted in MESG pretreated aortic rings. On the other hand, the inositol 1,4,5-triphosphate receptor, the ryanodine receptor, the Rho-kinase inhibitor (Y-27632), a soluble guanylyl cyclase blocker (1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one), and K⁺ channel blockers (glybenclamide, tetraethylammonium, and 4-aminopyridine) did not affect the effect of MESG. These results suggested that the mechanism underlying the vasorelaxant effect of MESG is mediated by endothelium-independent pathways. This specifically refers to blockade of the influx of extracellular Ca²⁺ via receptor-operative Ca²⁺ channels and voltage-dependent Ca²⁺ channels and inhibition of a protein kinase C-mediated cellular pathway.
authors.affiliation: Department of Herbology, College of Korean Medicine, Kyung Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul 130-701, Republic of Korea.
authors.forename: Kyungjin
authors.initials: K
authors.lastname: Lee
authors.forename: Jinho
authors.initials: J
authors.lastname: Jung
authors.forename: Gabsik
authors.initials: G
authors.lastname: Yang
authors.forename: Inhye
authors.initials: I
authors.lastname: Ham
authors.forename: Youngmin
authors.initials: Y
authors.lastname: Bu
authors.forename: Hocheol
authors.initials: H
authors.lastname: Kim
authors.forename: Ho-Young
authors.initials: HY
authors.lastname: Choi
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D019659:Asteraceae / Q000737:chemistry*; D020746:Calcium Channels, L-Type / Q000187:drug effects; D004730:Endothelium, Vascular / Q000502:physiology; D006162:Guanylate Cyclase / Q000378:metabolism; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology*; D015221:Potassium Channels / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000577:Amides; D020746:Calcium Channels, L-Type; D010703:Phorbol Esters; D010936:Plant Extracts; D015221:Potassium Channels; D011725:Pyridines; D014665:Vasodilator Agents; C108830:Y 27632; C119222:phorbol-12-myristate; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D054460:rho-Associated Kinases; D006162:Guanylate Cyclase; D009638:Norepinephrine
keywords: Sigesbeckia glabrescens; protein kinase C; rat aortic rings; receptor-operative Ca2+ channel; vasorelaxation; voltage-dependent Ca2+ channel