RESUMO
<p><b>OBJECTIVE</b>To investigate the vasorelaxant effect of puerarin in rat aortic rings and the mechanism.</p><p><b>METHOD</b>The isolated thoracic aortic rings of male Sprague-Dawley rats were mounted on the organ bath and the contractile responses of the vessel were recorded.</p><p><b>RESULT</b>Puerarin completely relaxed the contractions induced by phenylephrine in a concentration-dependent manner in endothelium-intact and endothelium-denuded rat aorta, but it had no effect on those preconstricted by a high concentration of potassium chloride (KCl, 60 mmol x L(-1)). The relaxant effect of puerarin was significantly inhibited by pretreatment of endothelium-denuded aorta with potassium channel antagonists tetraethylammonium, 4-aminopyridine but not glibenclamide.</p><p><b>CONCLUSION</b>Puerarin induces an endothelium-independent relaxation in rat aortic rings. The mechanisms may involve the reduction in Ca2+ influx through the calcium channels operated by alpha-adrenergic receptor and the activation of the potassium channels (Kv and BKca, but not KATP).</p>