Eicosanoids, or Icosanoids function as autocrine and paracrine mediators, and are oxygenated hydrophobic derivatives of 20-carbon polyunsaturated essential fatty acids, predominantly arachidonic acid (AA) in humans. Dihomo-gamma-linolenic acid (DGLA) and eicosapentaenoic acid (EPA, icosapentaenoic acid, timnodonic acid) also serve as eicosanoid precursors. Eicosanoids include leukotrienes with four double bonds and prostanoids with two double bonds (prostaglandins and prostacyclins with five-membered rings, and thromboxanes with heterocyclic oxane structures).

Eicosanoid biosynthesis begins with phospholipase catalyzed release from phospholipids (A2) or diacylglycerol (C) of a 20-carbon essential fatty acid (EFA) containing three, four, or five double bonds (ω-6 DGLA, ω-6 AA or ω-3 EPA, respectively).

Physiological activity of the short-lived eicosanoids is mediated by specific receptors:
● CysLT1 (Cysteinyl leukotriene receptor type 1)
● CysLT2 (Cysteinyl leukotriene receptor type 2)
● BLT1 (Leukotriene B4 receptor)
● PGD2: DP-(PGD2)
● PGE2:
● EP1-(PGE2)
● EP2-(PGE2)
● EP3-(PGE2)
● EP4-(PGE2)
● PGF2α: FP-(PGF2α)
● PGI2 (prostacyclin): IP-(PGI2)
● TXA2 (thromboxane): TP-(TXA2)

 Eicosanoid Actions



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