A functional cDNA clone for the mouse prostaglandin I PG) E receptor EP 2 subtype was isolated from a mouse cDNA library. The mouse EP2 receptor consists of 362 amino acid residues with seven putative transmembrane domains. [3H]PGE2 bound specifically to the membrane of Chinese hamster ovary tells stably expressing the cloned receptor. This binding was displaced by unlabeled prostanoids in the order of PGEz = I'GEt >> iloprost, a stable PGI 2 agonist > PGFz~ > PGDz. Binding was also inhibited by butaprost (an EP2 agonist) and to a lesser extent by M&B 28767 (an EP 3 agonist), but not by sulprostone (an EP~ and EP 3 agonis0 or SC-19220 (an EP~ antagonist). PGE 2 and butaprost increased the cAMP level in the Chinese hamster ovary cells in a concentration-dependent manner. Northvrn blot analysis revealed that EP 2 mRNA is expressed most abundantly in the uterus, followed by the spleen, lung, thymus, ileum, liver, and stomach.