Endothelium-Independent Vasorelaxant Effect of Lidocaine in Rat Aortic Rings

In the present study, lidocaine relaxed, in a concentration-dependent manner, the contractions induced by either phenylephrine or a high concentration of KCl (60 mM) in endothelium-intact rat aortic rings. Mechanical removal of endothelium did not significantly modify lidocaine-induced vasorelaxation. In endothelium-denuded aortic rings depolarized by 60 mM KCl, lidocaine inhibited Ca²⁺-induced contraction. Lidocaine also reduced the transient contraction elicited by phenylephrine in Ca²⁺-free medium. Pretreatment of endothelium-denuded aorta nonspecific K⁺with tetraethylammonium, a channel blocker, had no effect on the relaxant effect of lidocaine. These results indicate that lidocaine induces an endothelium-independent relaxation in rat aortic rings. The main mechanisms may include suppression in Ca²⁺through the voltage-sensitive Ca²⁺influx intracellular Ca²⁺channels and inhibition of release in the vascular smooth muscle cells.