Background: Beetroot has attracted much attention because of its blood pressure-lowering properties. Although beetroot contains various nutritional compounds, including inorganic nitrate, some of their physiological properties are not fully understood. In this study, we examined whether betanin, a beetroot component, has a regulatory effect on vascular tone.
Methods: Mechanical responses of isolated porcine coronary, mesenteric, and pulmonary arteries were assessed by organ chamber technique. In some cases, the vascular reactivity was observed in the presence of a physiological concentration of betanin (10 µM).
Results: Betanin did not induce vasorelaxation at physiological concentrations both in endothelium-intact and -denuded coronary, mesenteric, and pulmonary arteries. The endothelium-dependent agonists, bradykinin and A23187 induced vasorelaxation of endothelium-intact coronary arteries, both of which were not affected by exposure to betanin. Likewise, endothelium-independent vasorelaxation induced by sodium nitrite and sodium nitroprusside was also not affected by the presence of betanin. In addition, exposure of endothelium-intact coronary arteries to betanin did not attenuate prostaglandin F2α- and endothelin-1-induced vasocontraction.
Conclusions: These findings suggest that betanin does not have a vasorelaxant activity. It is unlikely that betanin is a component directly responsible for the beetroot-induced acute blood pressure-lowering effect in a nitrate-independent manner.
Keywords: beetroot; betanin; blood pressure; hypertension; vasorelaxation.
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