Prostaglandin (PG) E2 is involved in a number of physiological and pathophysiological events in many tissues throughout the body. The biological effects of PGE2 are mediated through interaction with specific membrane-bound G-protein coupled prostanoid EP receptors. There are four subtypes of the EP receptor, termed EP1, EP2, EP3 and EP4, which have been defined on the basis of their different pharmacological profiles and signal transduction pathways¹.

EP1 is characterized by the presence of a helical bundle consisting of seven hydrophobic transmembrane helices (TM1-TM7), which are connected through six alternating extracellular and intracellular loops. The N-terminus is located on the extracellular side of the membrane, whereas the C-terminus is located on the intracellular side².

EP1 receptors are thought to mediate contraction of smooth muscle in various tissues such as the gastrointestinal tract, respiratory tract, vas deferens, myometrium and the iris sphincter muscle and may also be important for absorption inhibition in the small intestine as well as enhancement of neuronal activity³.

Human colon cancer cells express the EP1 receptor. Furthermore, EP1 receptor antagonists inhibit chemically induced breast cancer development in rats and reduce the number of skin tumors per mouse following UVB exposure^4,5.