Prostaglandin E2 (PGE2) is formed in a variety of cells from prostaglandin H2, which is synthesized from arachidonic acid by the enzyme prostaglandin synthetase. PGE2 has a number of biological actions, including vasodilation, both anti- and proinflammatory action, modulation of sleep/wake cycles, and facilitation of human immunodeficiency virus replication. It elevates cAMP levels, stimulates bone resorption and has thermoregulatory effects. It has been shown to be a regulator of sodium excretion and renal hemodynamics.