The vascular effect of flavonoid isoquercitrin was investigated in the perfused mesenteric vascular bed of rats. In preparations with functional endothelium isoquercitrin (100, 300 and 1000nmol) dose-dependently reduced the perfusion pressure by 13±2.2, 33±3.9, and 58±3.7mm Hg, respectively. Endothelium removal or inhibition of the nitric oxide synthase enzymes by l-NAME did not change the effects of 100 and 300 nmol isoquercitrin, but reduced by 30-40% the vasodilation induced by 1000 nmol isoquercitrin. Perfusion with nutritive solution containing 40mM KCl abolished the vasodilatory effect of all isoquercitrin doses. Treatment with glibenclamide, a Kir6.1 (ATP-sensitive) potassium channel blocker, inhibited vasodilation induced by 100 and 300 nmol isoquercitrin, but only partially reduced the effect of 1000 nmol isoquercitrin. The non-selective KCa (calcium-activated) potassium channel blocker tetraethylammonium, but not the selective KCa1.1 channel blocker iberiotoxin, reduced by around 60% vasodilation induced by all isoquercitrin doses. In addition, association of tetraethylammonium and glibenclamide, or l-NAME and glibenclamide, fully inhibited isoquercitrin-induced vasodilation. Our study shows that isoquercitrin induces vasodilation in resistance arteries, an effect mediated by K(+) channel opening and endothelial nitric oxide production.
Keywords: Acetylcholine chloride (Pubchem CID 6060); Glibenclamide (PubChem CID: 3488); Iberiotoxin (PubChem CID 16132435); Indomethacin (PubChem CID 3715); Isoquercitrin; Isoquercitrin (PubChem CID 5280804); Mesenteric arterial bed; N-Nitroarginine methyl ester (PubChem CID 39836); Phenylephrine hydrochloride (PubChem CID: 5284443); Potassium channel; Tetraethylammonium chloride (PubChem CID 5946); Vasodilation.
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