Molecular Cloning and Characterization of Bovine Prostaglandin E2 Receptors EP2 and EP4: Expression and Regulation in Endometrium and Myometrium during the Estrous Cycle and Early Pregnancy

Prostaglandins (PGs) play important functions in the reproductive system, and PGE2 appears necessary for recognition of pregnancy. We have found that PGE2 is able to increase cAMP generation in the bovine endometrium. There are two PGE2 receptors (EP), EP2 and EP4, that are coupled to adenylate cyclase to generate cAMP, but these receptors have not been studied in the bovine. We have cloned and characterized bovine EP2 and EP4 receptors and studied their expression in the uterus. The amino acid sequences of bovine EP2 and EP4 possess a high degree (>80%) of identity with the other mammalian homologs. EP2 is expressed in most tissues, and EP4 is expressed only in intestine and testis. EP2 mRNA and protein are expressed in endometrium and myometrium during the estrous cycle, whereas EP4 is undetectable. The Western analysis indicates that EP2 is maximally expressed in both endometrium and myometrium between d 10 and 18 of the estrous cycle. Immunohistochemical localization reveals that EP2 protein is expres...