<P> In chemical structure, arachidonic acid is a carboxylic acid with a 20 - carbon chain and four cis - double bonds; the first double bond is located at the sixth carbon from the omega end . </P> <P> Some chemistry sources define' arachidonic acid' to designate any of the eicosatetraenoic acids . However, almost all writings in biology, medicine and nutrition limit the term to all - cis - 5, 8, 11, 14 - eicosatetraenoic acid . </P> <P> Arachidonic acid is a polyunsaturated fatty acid present in the phospholipids (especially phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositides) of membranes of the body's cells, and is abundant in the brain, muscles, and liver . Skeletal muscle is an especially active site of arachidonic acid retention, accounting for roughly 10 - 20% of the phospholipid fatty acid content on average . </P> <P> In addition to being involved in cellular signaling as a lipid second messenger involved in the regulation of signaling enzymes, such as PLC - γ, PLC - δ, and PKC - α, - β, and - γ isoforms, arachidonic acid is a key inflammatory intermediate and can also act as a vasodilator . (Note separate synthetic pathways, as described in section below .) </P>

Where is arachidonic acid stored in the body