Comparative Studies of KATP Channel Openers in Penile Erection: Minoxidil, Diazoxide and Pinacidil

Moon, Du Geon; Kim, Je Jong; Koh, Sung Kun

Abstract

PURPOSE: Currently available K+-channel openers are exclusively KATP channel openers. Among the KATP channel openers, minoxidil and diazoxide have been already used as antihypertensive agents clinically but their erectogenic activities have not been demonstrated. We performed this study to identify the effects of intracavernosal minoxidil and diazoxide on feline penile erection and also to compare that of pinacidil, relatively well-demonstrated K+-channel opener.
MATERIALS AND METHODS
Using a feline model, the magnitude of penile erection caused by pinacidil was compared with that caused by minoxidil and diazoxide. With control erectile responses of intracavernosal PGE1 and papaverine, synergistic effects of erectogenic agents with KATP channel openers were also investigated in twenty-eight male cats in vivo.
RESULTS
Intracavernosal injection of pinacidil increased intracavernosal pressure (ICP) in a dose-dependent fashion but minoxidil and diazoxide did not affect ICP significantly. Furthermore, pinacidil (10-5M/ml) enhanced the increase of ICP by PGE1 or papaverine but minoxidil and diazoxide did not. Noteworthy, pinacidil induced cavernous relaxation to the following erectogenic agents even in refractory cases to higher concentration (10-1M/ml) of erectogenic agent alone (n=7, p<0.01).
CONCLUSIONS
These result suggests that minoxidil and diazoxide, which have been used as antihypertensive agents clinically, do not affect intracavernosal pressure. Among the KATP channel openers, pinacidil seems to be promising in producing penile erection as an alternate component of previous intracavernous injection. Also, pinacidil may be useful clinically because of the potential therapeutic effects as an intracavernosal agents in combination with PGE1 or papaverine.