Eicosanoids are a family of powerful, short-lived hormone-like compounds produced in the body from essential fatty acids. They are responsible for many of the benefits of essential fatty acids. Some eicosanoids, however, are potentially harmful if excessive amounts build up in the body. Arachidonic Acid (AA), is an eicosanoid derived from omega 6 fatty acid that can be potentially harmful if excessive amounts build up in the body.
Prostaglandins, derived from both omega 6 and omega 3, regulate cellular activity on a moment to moment basis. They regulate heart rate, blood pressure, blood clotting, fertility, conception, inflammatory responses, insulin sensitivity, immune responses, anabolic/catabolic process and hundreds of other functions known and yet unknown. There are three series of prostaglandins.
Both series 1 and series 2 prostaglandins are eicosanoids derived from the same precursor, linoleic acid (omega-6 essential fatty acid), while series 3 prostaglandins, or PGE3, are derived from linolenic acid (omega-3 essentail fatty acid). PGE1 is derived from gamma linolenic acid (GLA) - a non-essential fatty acid which can be produced from Omega 6 or consumed directly as in Evening Primrose oil
Series 1 prostaglandins promote performance. Series 2 prostaglandins disrupt performance and series 3 prostaglandins block the formation of series 2 prostaglandins. Since most of our diets are rich in omega 6 and deficient in omega 3, an unhealthy balance is created. The body must maintain a delicate balance between these three prostaglandins. The body must produce enough beneficial eicosanoids such as PGE1 and PGE3, otherwise the strong pro-inflammatory, blood-vesel-constricting and blood-clotting effects of PGE2 will overwhelm the system. It is for this reason you want to maintain the proper balance of Omega 3 and Omega 6 essential fatty acids in your diet. (http://www.mens-total-fitness.com/eicosanoids.html)