Presence of PGE1 binding determines the erectile response to PGE1

The clinical benefit of PGE1 in erectile dysfunction in men is well proven, while other species including non-human primates show almost no response. The reason for that difference is still unclear. We examined PGE1 binding in human surgical material (n=27) and from transsexual surgery (n=7) as well as rhesus (n=10) and cynomolgus monkeys (n=8) corpus cavernosum tissue. Erection was judged after intracavernous injection of PGE1 in men (10 microg) and in monkeys (5 microg). Human corpus cavernosum shows high- (binding capacity 24.7+/-3.3 pmol/mg protein) and low-affinity (binding capacity 77.4+/-7.3 pmol/mg protein) PGE1 binding sites. Oestrogen (3 mg/day) for more than one month before transsexual surgery decreases receptor density significantly. In rhesus and cynomolgus monkeys no high-affinity binding could be detected, while they respond on PGE1 with slight tumescence only. These findings indicate a significant correlation between corpus cavernosum PGE1 receptor density and the erectile response.