Prostaglandins and other eicosanoids

Earlier observation that human seminal fluid exerts direct muscle eontractions of uterine tissues was thought to be eaused by an acidic vasoactive substance produced in the prostate gland, that was subsequently named as prostaglandin (referred to as PG). It was revealed later on that the aeidie substanee eontained a number of structurally similar prostaglandin products. 

Prostaglandins (IGA through PGF) are a group of cyclopentane derivatives formed from 20-carbon polyunsaturated fatty aeids. They exert a good number of physiologic properties. They are usually termed as local hormones because of the two cardinal facts, namely /irst, they influence biologic processes near their point of release and secondly, they display mechanisms for their inactivation near the locus of release. 

Prostaglandin (PG) is based on the following hypothetical compoimd prostanoic acid  

A-type compounds E-type compounds F-type compounds a-designation 

PG of F series (containing 2 ring OH fimctions) having the OH at C-9 in the a-configuration and 2 double-bonds at C-5 and C-13, 

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Wang D, Mann JR, DuBois RN The role of prostaglandins and other eicosanoids in the gastrointestinal tract. Gastroenterology 2005 128 1445. [PMID 15887126]... 

Cyclooxygenase (COX), one of the two activities of prostaglandin endoperoxide synthase (PGHS), is the key enzyme in the conversion of arachidonic acid derived from lipids of the cell membrane to prostaglandins and other eicosanoids (Fig. 3). 

The biosynthetic pathway of prostaglandins and other eicosanoids is outlined in Figure 15-2. Basically, these compounds are derived from a 20-carbon essential fatty acid. In humans, this fatty acid is usually arachi-donic acid,68,73 which is ingested in the diet and stored as a phospholipid in the cell membrane. Thus, the cell has an abundant and easily accessible supply of this... 

The most important known effects of the prostaglandins and other eicosanoids are the contraction and relaxation of smooth muscles ... 

The early stages in the biosynthesis of prostaglandins and other eicosanoids in mammals are outlined in Scheme 6. From what is known at this stage, the pathway is very similar in invertebrates.130... 

C. St. Stiirzebecher, M. Haberey, B. Muller, E. Schillinger, G. Schroder, W. Skuballa, and G. Stock, K. Schror, Ed., Prostaglandins and Other Eicosanoids in the Cardiovascular Slys-tem, Karger, Basel, Switzerland, 1985, pp. 485-491. 

Prostaglandins and other Eicosanoids (ii) Antilipedemic Drugs Hi) Hormone Antagonists... 

Stanley-Samuelson, D.W. (1987) Physiological roles of prostaglandins and other eicosanoids in invertebrates. Biol. Bull. Woods Hole, 173,92-109... 

Figure 1. There are two important families of PUFA the n-6 family based on linoleic add, and the n-3 family based on a-linolenic acid. Since animals - including humans - cannot produce linoleic or a-linolenic acids themselves, these acids are essential parts of the diet, obtainable only from vegetable sources or from animals which have already derived these acids from a plant source. Once ingested, the two Cjj acids can be metabolized to important and acids through a series of changes involving desaturation and elongation. The same enzymes are required for both famiUes of adds and there is competition for these. The most important acids in these sequences are arachidonic addin the h-6 series, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the n-3 series. All these adds are important components of phospholipid membranes, and the two acids are also precursors of prostaglandins and other eicosanoids. The locations of the double bonds are indicated in brackets after the abbreviated structure of each fatty acid.

Some viruses affect the metabolism of arachidonic acid (20 4(06), including the production of prostaglandins and other eicosanoids involved in mammalian immune responses to microbial infection (318-321). A recent report supports the presence of at least one gene in orthopoxviruses that redirects host eicosanoid metabolism, and these metabolites are an obligate requirement for viral replication (322). Fatty acid oxygenase products are discussed in more detail below. 

DiBenedetto FE, Bito LZ. Transport of prostaglandins and other eicosanoids by the choroid plexus its characterization and physiological significance. J Neurochem 1986 46 1725-1731. 

Pickard, J. D., Walker, V., 1984b Current concepts of the role of prostaglandins and other eicosanoids in acute cerebrovascular disease. In Neurotransmitters and the Cerebral Circulation. LERS (MacKenzie, E. T., ed.), V0I.2, pp. 191-218. New York Raven Press. 

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