Eicosanoids
o Eicosanoids are 20 carbon molecules derived mainly from
Arachidonic Acid (AA).
Eicosanoids are classified into four groups: (1)
Prostaglandins (PG) and prostacyclins (PGI), and (2)
thromboxanes (TX); a third type is the leukotrienes (LT)
and a fourth is and lipoxins (LX).
o Prostaglandins and thromboxanes are known as
prostanoids.
They are produced from ω-3 and ω-6 polyunsaturated FA
with 20 carbons (eicosa = 20).
o From essential fatty acids like: linoleic fatty acids
They elicit physiologic (inflammatory) and pathologic
(hypersensitivity) responses:
o Gastric integrity, renal function, smooth muscle
contraction (intestine and uterus), blood vessel
diameter (dilation and constriction), and platelet
homeostasis.
They are not stored.
They have a short half-life.
They are rapidly metabolized to inactive products.
o They are not considered hormones even though they
act like them, because they aren’t stored and they
work in the vicinity (in the neighborhood of cells) and locally (they don’t travel
in the blood).
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, Reasons for naming
Site of synthesis:
o Prostaglandins were originally shown to be synthesized in the prostate
gland then it turned out that they’re produced by different tissues.
o Thromboxanes from platelets (thrombocytes: name of platelets)
o Leukotrienes from leukocytes.
o Lipoxins are inflammation resolving eicosanoids synthesized
through lipoxygenase interactions.
Synthesis from arachidonic acid
Arachidonic Acid (an eicosatetraenoic FA), is the
immediate precursor of PG (AKA series 2 or
those with two double bonds).
AA is derived by the elongation (addition of
acetyl CoA) and desaturation of the linoleic
acid.
AA is incorporated into membrane
phospholipids (typically PI) at carbon 2 and
released by phospholipase A2.
Remember PI (Phosphatidylinositol) composed
of glycerol backbone + stearic acid on C1 + AA
on C2 + inositol group on C3
2|Page
o Eicosanoids are 20 carbon molecules derived mainly from
Arachidonic Acid (AA).
Eicosanoids are classified into four groups: (1)
Prostaglandins (PG) and prostacyclins (PGI), and (2)
thromboxanes (TX); a third type is the leukotrienes (LT)
and a fourth is and lipoxins (LX).
o Prostaglandins and thromboxanes are known as
prostanoids.
They are produced from ω-3 and ω-6 polyunsaturated FA
with 20 carbons (eicosa = 20).
o From essential fatty acids like: linoleic fatty acids
They elicit physiologic (inflammatory) and pathologic
(hypersensitivity) responses:
o Gastric integrity, renal function, smooth muscle
contraction (intestine and uterus), blood vessel
diameter (dilation and constriction), and platelet
homeostasis.
They are not stored.
They have a short half-life.
They are rapidly metabolized to inactive products.
o They are not considered hormones even though they
act like them, because they aren’t stored and they
work in the vicinity (in the neighborhood of cells) and locally (they don’t travel
in the blood).
1|Page
, Reasons for naming
Site of synthesis:
o Prostaglandins were originally shown to be synthesized in the prostate
gland then it turned out that they’re produced by different tissues.
o Thromboxanes from platelets (thrombocytes: name of platelets)
o Leukotrienes from leukocytes.
o Lipoxins are inflammation resolving eicosanoids synthesized
through lipoxygenase interactions.
Synthesis from arachidonic acid
Arachidonic Acid (an eicosatetraenoic FA), is the
immediate precursor of PG (AKA series 2 or
those with two double bonds).
AA is derived by the elongation (addition of
acetyl CoA) and desaturation of the linoleic
acid.
AA is incorporated into membrane
phospholipids (typically PI) at carbon 2 and
released by phospholipase A2.
Remember PI (Phosphatidylinositol) composed
of glycerol backbone + stearic acid on C1 + AA
on C2 + inositol group on C3
2|Page
