Prostaglandin E2 (PGE2) is a primary product of arachidonic acid metabolism in many cells. Like most eicosanoids, it does not exist preformed in any cellular reservoir. When cells are activated or exogenous free arachidonate is supplied, PGE2 is synthesized de novo and released into the extracellular space. In vivo, PGE2 is rapidly converted to an inactive metabolite (13,14-dihydro-15-keto PGE2) by the prostaglandin 15-dehydrogenase pathway. The half-life of PGE2 in the circulatory system is approximately 30 seconds and normal plasma levels are 3-12 pg/ml. Our PGE2 ELISA has been validated for use with urine, plasma, and culture media samples. In general, urine and culture media samples can be diluted, if necessary, and added directly to the assay well. Plasma samples should be purified prior to use. Because of the rapid metabolism of PGE2, the determination of in vivo PGE2 biosynthesis is often best accomplished by the measurement of PGE2 metabolites. Our Prostaglandin E Metabolite assay (Cay-514531) converts all major PGE2 metabolites into a single stable derivative which is easily measurable by ELISA.