Materials and Methods: To identify PDE messenger RNA in human cavernous tissue, we constructed primers for 14 published PDE isoforms. Expression of the genes was then analyzed by reverse transcriptase polymerase chain reaction under standard conditions and by subsequent sequencing.

Results: Messenger RNA was detected in human corpus cavernosum for the human phosphodiesterase isoenzymes and isoforms PDE1A, PDE1B, PDE1C, PDE2A, PDE3A, PDE4A, PDE4B, PDE4C, PDE4D, PDE5A, PDE7A, PDE8A and PDE9A.

Conclusions: A total of 13 PDE genes were expressed in human cavernous tissue, indicating a role of these enzymes in penile erection regulation. The intracellular mechanisms of hydrolyzing cyclic adenosine monophosphate and cyclic guanosine monophosphate by PDEs are more complex than assumed previously. These findings open up new possibilities in the development of drugs for the treatment of erectile dysfunction.