Isosteviol acts on potassium channels to relax isolated aortic strips of Wistar rat.
Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, which is commonly used as a noncaloric sugar substitute in Japan and Brazil. In the present study, the role of potassium channels in the vasodilator effect of isosteviol was investigated using potassium channel blockers on isosteviol-induced relaxation of isolated aortic rings prepared from Wistar rats. Isosteviol dose-dependently relaxed the vasopressin (10(-8) M)-induced vasoconstriction in isolated aortic rings with or without endothelium. However, in the presence of potassium chloride (3x10(-2) M), the vasodilator effect of isosteviol on arterial strips disappeared. Only the inhibitors specific for the ATP-sensitive potassium (K(ATP)) channel or small conductance calcium-activated potassium (SK(Ca)) channel inhibited the vasodilator effect of isosteviol in isolated aortic rings contracted with 10(-8) M vasopressin. Also; since the isosteviol-induced relaxation was unchanged by methylene blue, a role of nitric oxide and/or endothelium in the vasodilatation produced by isosteviol could be ruled out. The obtained results indicated that vasodilatation induced by isosteviol is related to the opening of SK(Ca) and K(ATP) channels.
Graduate Institute of Medical Science, Taipei Medical University, Taipei 106, Taiwan.
Kar-Lok
KL
Wong
Paul
P
Chan
Hung-Yu
HY
Yang
Feng-Lin
FL
Hsu
I-Min
IM
Liu
Yu-Wan
YW
Cheng
Juei-Tang
JT
Cheng
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology*; D004224:Diterpenes / Q000378:metabolism / Q000494:pharmacology*; D045786:Diterpenes, Kaurane; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D015394:Molecular Structure; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014664:Vasodilation
D004224:Diterpenes; D045786:Diterpenes, Kaurane; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C012042:steviol; D006162:Guanylate Cyclase