Pharmacological and functional characterization of novel EP and DP receptor agonists: DP1 receptor mediates penile erection in multiple species.
BACKGROUND
Despite the widespread use of prostaglandin E(1) as an efficacious treatment for male erectile dysfunction for more than two decades, research on prostanoid function in penile physiology has been limited.


OBJECTIVE
To characterize the pharmacological and physiological activity of novel subtype-selective EP and DP receptor agonists.


METHODS
Radioligand binding and second messenger assays were used to define receptor subtype specificity of the EP and DP agonists. Functional activity was further characterized using isolated human and rabbit penile cavernosal tissue in organ baths. In vivo activity was assessed in rabbits and rats by measuring changes in cavernous pressure after intracavernosal injection of receptor agonists.


METHODS
Receptor binding and signal transduction, smooth muscle contractile activity, erectile function.


RESULTS
In organ bath preparations of human cavernosal tissue contracted with phenylephrine, EP2- and EP4-selective agonists exhibited variable potency in causing relaxation. One of the compounds caused mild contraction, and none of the compounds was as effective as PGE(1) (EC(50) = 0.23 microM). There was no consistent correlation between the pharmacological profile (receptor binding and second messenger assays) of the EP agonists and their effect on cavernosal tissue tone. In contrast, the DP1-selective agonist AS702224 (EC(50) =29 nM) was more effective in relaxing human cavernosal tissue than either PGE(1), PGD(2) (EC(50) = 58 nM), or the DP agonist BW245C (EC(50) =59 nM). In rabbit cavernosal tissue, PGE(1) and PGD(2) caused only contraction, while AS702224 and BW245C caused relaxation. Intracavernosal administration of AS702224 and BW245C also caused penile tumescence in rabbits and rats. For each compound, the erectile response improved with increasing dose and was significantly higher than vehicle alone.


CONCLUSIONS
These data suggest that AS702224 is a potent DP1-selective agonist that causes penile erection. The DP1 receptor mediates relaxation in human cavernosal tissue, and stimulates pro-erectile responses in rat and rabbit. Thus, rabbits and rats can be useful models for investigating the physiological function of DP1 receptors.
EMD Serono Research Institute-Medicinal Chemistry, Rockland, MA, USA.
Nadia
N
Brugger
Noel N
NN
Kim
Gian Luca
GL
Araldi
Abdulmaged M
AM
Traish
Stephen S
SS
Palmer
D000368:Aged; D000527:Alprostadil / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006827:Hydantoins / Q000494:pharmacology; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000187:drug effects*; D010410:Penile Erection / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D015230:Prostaglandin D2 / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D011982:Receptors, Prostaglandin / Q000819:agonists*; D018078:Receptors, Prostaglandin E / Q000819:agonists* / Q000502:physiology; D058307:Receptors, Prostaglandin E, EP2 Subtype; D013045:Species Specificity; D014665:Vasodilator Agents / Q000494:pharmacology
D006827:Hydantoins; C545644:PTGER2 protein, human; D010726:Phosphodiesterase Inhibitors; C545646:Ptger2 protein, rat; D011982:Receptors, Prostaglandin; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D014665:Vasodilator Agents; C501562:prostanoid D receptor 1, human; D010656:Phenylephrine; C030669:BW 245C; D000527:Alprostadil; D015230:Prostaglandin D2