Involvement of protein kinase C and Na+/K+-ATPase the contractile response induced by myricetin in rat isolated aorta

The role of PKC and Na+/K+-ATPase in the vascular smooth muscle responses induced by the bioflavonoid myricetin was investigated. KC1 induced a concentration-dependent relaxation in arteries exposed to K+-free solution that was mainly mediated by an activation of Na+/K+-ATPase. Myricetin (50 muM) partially inhibited this vasorelaxant effect induced by KC1 in intact rings, being unaffected in the endothelium-denuded rings. This inhibitory effect induced by myricetin was suppressed by the PGH(2)-TXA(2) receptor antagonist, SQ 29,548, and the PKC inhibitor, staurosporine. Myricetin also induced an endothelium-dependent contractile response which was increased in the presence of PMA and reduced by staurosporine. In conclusion, myricetin both modulates Na+/K+-ATPase-induced vasodilatation acting as a functional inhibitor of Na+/K+-ATPase activity and activates protein kinases, including PKC, to induce contraction. These effects appear to be related to the activation of PGH(2)-TXA(2) receptors on vascular smooth muscle by the TXA(2) released from endothelium.