Contraction and relaxation induced by some prostanoids in isolated human penile erectile tissue and cavernous artery

Abstract

Contractant and relaxant effects of prostaglandins (PG) F2 alpha, E1 and E2, prostacyclin (PGI2), the thromboxane A2 agonist U46619 and the prostaglandin endoperoxide analogue U44069 were investigated in isolated preparations of the human corpus cavernosum, corpus spongiosum and cavernous artery. In corpus cavernosum and corpus spongiosum preparations, PGF2 alpha produced concentration-dependent contractions showing rhythmic variations in tension. The contractions were effectively relaxed by carbachol and vasoactive intestinal polypeptide. U46619, U44069 and PGI2 also contracted corpus cavernosum and corpus spongiosum strips at resting tension, U46619 being the most potent drug. PGE1 and PGE2, but not PGI2 relaxed corpus cavernosum and corpus spongiosum preparations contracted by noradrenaline (NA) and PGF2 alpha. PGE1 was the more effective agent; high concentrations of PGE2 produced contraction. In cavernous artery segments, PGF2 alpha produced concentration-dependent contractions. No oscillations in tension were observed; carbachol had no relaxant action, but VIP effectively relaxed the vessels. U46619 and U44069, but not PGI2 had contractant effects on cavernous artery segments at resting tension. PGE1 and PGI2, but not PGE2 relaxed NA contracted vessel preparations; all agents (PGE2 less effectively) relaxed PGF2 alpha contracted vessel segments. It is concluded that cavernous artery and erectile tissue proper (corpus cavernosum and corpus spongiosum) differ importantly in their reaction to various prostanoids. It cannot be excluded that products of the arachidonate cascade can be involved in the control of penile tumescence and erection.