Functional prostaglandin E (EP) receptors in human penile corpus cavernosum

In this study, we have characterized functional EP receptors in human corpus cavernosum (HCC) tissue and in HCC smooth muscle cells (SMC). Using RNase protection assays, we determined expression of EP2, EP3I and EP3II receptor mRNA. In organ bath preparations of HCC tissue strips, PGE1 caused dose-dependent relaxation at concentrations below 300 nM. At concentrations greater than 300 nM, PGE1 caused contraction. Addition of the EP1/EP2/EP3 receptor antagonist AH6809 inhibited this contraction and facilitated further relaxation through concentrations above 1 microM of PGE1. The EP1/EP3 receptor selective agonist 17-phenyltrinor-PGE2 caused dose-dependent contraction that was partially attenuated by SC51322, an EP1 selective antagonist. In cultures of HCC SMC, PGE1 stimulated cAMP accumulation in a dose-dependent manner. Interestingly, AH6809 significantly attenuated PGE1-induced cAMP accumulation. Sulprostone, a selective EP3 receptor agonist, induced weak contractions in HCC tissue strips but augmented forskolin-induced cAMP synthesis in HCC SMC. The data in this study suggest that HCC and cultured smooth muscle cells express EP1, EP2 and EP3 receptors. These receptors mediate their responses via different biochemical pathways and are expected to have different responses in regulating smooth muscle tone. Thus, we suggest that the ultimate response in erectile tissue to various prostanoids is the integration of responses elicited by individual EP receptor subtypes to a given ligand.