Quantitative Analysis of Vasodilatory Action of Quercetin on Intramural Coronary Resistance Arteries of the Rat In Vitro

Background

Dietary quercetin improves cardiovascular health, relaxes some vascular smooth muscle and has been demonstrated to serve as a substrate for the cyclooxygenase enzyme.

Aims

1. To test quantitatively a potential direct vasodilatory effect on intramural coronary resistance artery segments, in different concentrations. 2. To scale vasorelaxation at different intraluminal pressure loads on such vessels of different size. 3. To test the potential role of prostanoids in vasodilatation induced by quercetin.

Methods

Coronary arterioles (70–240 µm) were prepared from 24 rats and pressurized in PSS, using a pressure microangiometer.

Results

The spontaneous tone that developed at 50 mmHg was relaxed by quercetin in the 10⁻⁹ moles/lit concentration (p<0.05), while 10⁻⁵ moles/lit caused full relaxation. Significant relaxation was observed at all pressure levels (10–100 mmHg) at 10⁻⁷ moles/lit concentration of quercetin. The cyclooxygenase blocker indomethacin (10⁻⁵moles/lit) induced no relaxation but contraction when physiological concentrations of quercetin were present in the tissue bath (p<0.02 with Anova), this contraction being more prominent in smaller vessels and in the higher pressure range (p<0.05, Pearson correlation). A further 2–8% contraction could be elicited by the NO blocker L-NAME (10⁻⁴ moles/lit).

Conclusion

These results demonstrate that circulating levels of quercetin (10⁻⁷ moles/lit) exhibit a substantial coronary vasodilatory effect. The extent of it is commeasurable with that of several other physiological mechanisms of coronary blood flow control. At least part of this relaxation is the result of an altered balance toward the production of endogenous vasodilatory prostanoids in the coronary arteriole wall.