Prostaglandins numbering system

The omega (<0) numbering system is also used for unsaturated fatty acids. The co-family describes the position of the last double bond relative to the end of the chain. The omega designation identifies the major precursor fatty add, e.g., arachidonic add is formed from linoleic acid (co-6 family). Arachidonic acid is itself an important precursor for prostaglandins, thromboxanes, and leukotrienes. 

Because renal vasodilatation and hyperfiltration are often associated with a natriuretic response, a number of activators or inhibitors of endogenous vasoactive systems can cause increased NaCl excretion, and some of these may be developed into compounds of clinical interest in special situations. Such agents include natriuretic pqDtides most notably B-type natriuretic peptide (nesiritide), neutral endopeptidase (NEP) inhibitors (thiorphan, phosphoramidon), mixed NEP and ACE inhibitors (omapatrilat), guanylin and uroguanylin, kinins, prostaglandins of the E series, adrenomedullin, relaxin, prolactin, and others. 

Prostaglandins are a group of lipid autacoids known as eicosanoids. They are produced from membrane phospholipids and found in almost every tissue and body fluid. They are involved in a number of physiological processes including inflammation, smooth muscle tone and gastrointestinal secretion. In the central nervous system they have been reported to produce both excitation and inhibition of neuronal activity. 

The cytochrome P450 (CYP450) enzyme superfamily is the primary phase I enzyme system involved in the oxidative metabolism of drugs and other chemicals. These enzymes also are responsible for all or part of the metabolism and synthesis of a number of endogenous compounds, such as steroid hormones and prostaglandins. 

Leukocytes typically express minimal amounts of procoagulant activity in the unstimulated state (55). Cytokines such as interleukin-1 (IL-1) and tumor necrosis factor (TNF) can elicit the expression of tissue factor on endothelial and mononuclear cells (56). Monocyte procoagulant activity is also induced by endotoxin, the complement system, phorbol esters, prostaglandins, and a number of other agonists (57). Procoagulant activity associated with leukocytes is not limited... 

Strengthens the immune system and tolerance to infections (limits synthesis of prostaglandins, depresses number of free radicals)... 

Individual prostaglandins are described by a system of abbreviation in which the name prostaglandin is designated PG, followed by a third letter (A-I) that indicates the nature of the substituents on the cyclopentane ring. A numerical subscript indicates the total number of double bonds in the aliphatic chains. 

---