Prostaglandins and Related Substances

Important essential fatty acids in the diet are linoleic acid (cis,cis-9,12-octadecadienoic acid, 18 2d9,12) and a-linolenic acid (all-cis-9,12,15-octadecatrienoic acid 18 3d9,12,15). The numbering in this conventional system begins with the carboxyl group. The short hand, for example 18 2d9,12, indicates 18 carbon atoms, with two double bonds located between carbon atoms 9 and 10 and 12 and 13. There is an alternative system of numbering in which fatty acids are numbered from the methyl (or a ) terminal. In this case, linoleic acid is designated a -6,9-octadecadienoic acid (18 2ft)6), and a-linolenic acid is o -3,6,9-octadecatrienoic acid (18 3ft)3). This serves to designate two unsaturated fatty acid families, the ft)6 and the a families. 

The mammalian organism is unable to introduce double bonds at a3 and u6 of fatty acids, and this is probably why these families must be present in the diet. These fatty acids can be desaturated and elongated (see Chapter 19) to form derived essential fatty acids, dihomo-T-linoleic acid (20 3o 6), arachidonic acid (20 4ft)6), and eicosapentaenoic acid (20 5ft 3), the three direct precursor acids of PGs. Dihomo-r-linoleic acid, an intermediate in the biosynthesis of arachidonic acid from linoleic acid, is the precursor of PGs of the 1 series. Arachidonic acid and eicosapentaenoic acid are precursors of PGs of the 2 series and 3 series, respectively. 

Interest in eicosapentaenoic acid (EPA, 20 5ft)3) arose from the observation that the Eskimos of Greenland have low incidences of acute myocardial infarction and atherosclerosis, and an increased tendency to bruise and bleed, includ- 

Because arachidonic acid and compounds of the 2 series are predominant in humans, we direct our consideration primarily to these compounds, keeping in mind that biologically active 1 and 3 series compounds are also produced. Likewise, it is far beyond the scope of our discussion here to consider all the possible products of the C20 polyunsaturated fatty acids and their metabolites. 

Very little free AA is found in unstimulated cells. AA, like other polyunsaturated fatty acids, is esterified almost exclusively to membrane phospholipids in the 2-acyl position. Different cells release AA in response to a number of stimuli, such 

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Yamamoto, S. (1983). In Prostaglandins and Related Substances (eds. C. Pace-Ascieak and E. Grandstrom) pp. 171-202. Elsevier, Amsterdam. 

S. Yamamoto, Enzymes in the arachidonic acid cascade. In C.Pace-Asciak and E.Granstrom (eds.), Prostaglandins and Related Substances. Elsevier, Amsterdam etc., 1983, pp. 95-126. 

R. A Coleman, Prostaglandins and Related Substances—A Practical Approach, IRL Press, Oxford, 1987, pp. 267-303. 

Volume 5. Prostaglandins and Related Substances (1983) C. Pace-Asciak and E. Granstrom (Eds.)... 

Pace -Asdak/Granstrom (eds.) Prostaglandins and related substances Elsevier Science Publishers B. K, 1983... 

Benedetto, C., McDonald-Gibson, R.G., Nigam, S. and Slater, T.F. (editors) Prostaglandins and Related Substances. A Practical Approach (1987) IRL Press Ltd, Oxford. 

Manku, M. S., Oka, M., and Horrobin, D. F., 1979, Differential regulation of the formation of prostaglandins and related substances from arachidonic acid and from dihomogammalinolenic acid. II. Effects of vitamin C, Prostaglandins Med. 3 129-137. 

Slater, TF and McDonald-Gibson, RG (1987) Introduction to the eicosanoids. In Prostaglandins and Related Substances A Practical Approach (C Benedetto, RG McDonanld-Gibson, S Nigam and TF Slater, eds), IRL Press, Oxford, pp.1-4. 

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