Prostaglandins are produced by the metabolism of arachidonic acid. Prostaglandin E2 is one of the five physiologically significant prostanoids known. Its wide spectrum of physiologic and pharmacologic effects in various tissues is mediated through binding to the Prostaglandin E2 receptors (EP1, EP2, EP3 & EP4). These include effects on the immune, endocrine, cardiovascular, renal and reproductive systems as well as smooth muscle. It is also one of the most abundant of the prostanoid family in the brain where it plays an important role in many neural functions, particularly in newborn babies, and as a mediator of inflammation. Prostaglandin E2 signals through a family of G-protein coupled receptors known as EP receptors. There are 4 subtypes of EP receptors, known as EP1, EP2, EP3 and EP4. EP2 receptors are 358 amino acid proteins with a short third intracellular loop. EP2 receptors stimulate adenylyl cyclase by their coupling to Gs and do not undergo Prostaglandin E2 induced internalization. The EP2 receptors is involved with the contration and relaxation of smooth muscle tissue. These receptors are mainly localized in lung and placental tissues and in smooth muscle.