Butaprost, a structural analog of PGE2, is a selective agonist for the EP2 receptor subtype. EP2 receptors are expressed on human neutrophils and on respiratory, vascular, and uterine smooth muscle. Butaprost binds with about 1/10 the affinity of PGE2 to the recombinant murine EP2 receptor, and does not bind appreciably to any of the other murine EP receptors or DP, TP, FP, or IP receptors. The EC50 for the stimulation of cAMP by butaprost in COS cells transfected with the human EP2 receptor is about 5 µM, while the EC50 for PGE2 in this assay is about 43 nM. Butaprost has frequently been used to pharmacologically define the EP receptor expression profile of various human and animal tissues and cells.