Effect of Rho-kinase inhibition on vasoconstriction in the penile circulation

A recent report from this laboratory (Chitaley K, Wingard C, Webb R, Branam H, Stopper V, Lewis R, and Mills T. Nature Medicine 7: 119-122, 2001) show ed that inhibition of Rho-kinase increased the erectile response (intracave rnosal pressure and mean arterial pressure) by a process that does not requ ire nitric oxide or cGMP. The present study investigated whether vasoconstr ictor agents, which are active in the penis, act via the Rho-kinase pathway . Western analysis revealed RhoA and Rho-kinase protein in the penis. Treat ment with the selective Rho-kinase inhibitor Y-27632 significantly increase d the magnitude of the erectile response. Intracavernous administration of endothelin-1 (ET-1; 50 pmol) or methoxamine (10 mug/kg) reduced the erectil e response to autonomic stimulation. If Y-27632 was given before ET-1 or me thoxamine, the vasoconstrictor effect was reduced, and intracavernosal pres sure and mean arterial pressure remained elevated. However, when given afte r methoxamine, Y-27632 had a reduced vasodilatory effect, and Y-27632 had n o vasodilatory effect when given after ET-1. These findings suggest that ET -1 and methoxamine increase Rho-kinase activity in the cavernous circulatio n and support the hypothesis that the vasoconstriction that maintains the p enis in the nonerect state is mediated, in part, by the Rho-kinase pathway.