Cardiovascular Effects of Isorhamnetin and Quercetin in Isolated Rat and Porcine Vascular Smooth Muscle and Isolated Rat Atria

Abstract

Isorhamnetin and quercetin produced endothelium-independent vasodilator effects in rat aorta, rat mesenteric arteries, rat portal vein and porcine coronary arteries. The effects of the two flavonoids were similar in arteries stimulated by noradrenaline, KCl, U46619 or phorbol esters but the two flavonoids were more potent in the coronary arteries than in the aorta. At high concentrations, they also induced a positive inotropic effect in isolated rat atria. Therefore, at least part of the in vivo effects of quercetin may result from its conversion to isorhamnetin which is the main metabolite of quercetin found in plasma. The arterial, venous and coronary vasodilator effects may contribute to the protective effects of flavonoids in ischaemic heart disease observed in epidemiological studies.

Abbreviations

cyclic AMP:Adenosine 3′:5′-cyclic monophosphate

cyclic GMP:Guanosine 3′:5′-cyclic monophosphate

E_max:Maximal effect

NO:Nitric oxide

pD₂:Half-maximal effective concentration (as -log[M])

PMA:Phorbol 12-myristate-13-acetate

S.E.M.:Standard Error of the Mean

SIN-1:3-Morpholino-sydnonimine

SNP:Sodium nitroprusside

U46619:Thromboxane A₂ mimetic

Key words

Quercetin - isorhamnetin - atria - coronary artery - portal vein

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