Phosphodiesterase 2A is a cGMP stimulated, cAMP/cGMP dual-specific phosphodiesterase whose hydrolytic activity is stimulated by the presence of cGMP binding to the GAF domain. PDE2A has been implicated in penile erectile dysfunction and in the regulation of fluid and inflammatory cell transit across the endothelial cell barrier (i.e., venous and capillary). PDE2A activity is inhibited by erythro-9-(2-hydroxyl-3-nonyl)adenine (EHNA). At least three isoforms have been reported (PDE2A1, PDE2A2, and PDE2A3).