biochem eicosanoids

7/27/2019 Biochem Eicosanoids

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EicosanoidsProstaglandin, Leukotriene, Thromboxane


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What are Eicosanoids?

They are signaling molecules made by oxidation of20-carbon fatty acids.

They exert complex control over many bodily

systems, mainly in inflammation or immunity, andas messengers in the central nervous system.

They are hormone-like substances present inmany tissues and body fluids.

They are not hormones as they are not producedby glands. They are made by a chemical reactionat the site where they are needed and can bemade in nearly all the organs in the body.


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Eicosanoids

regulation of platelet aggregation

lowering of blood pressure

regulation of body temperature function of nerve transmission

action of certain hormones

control of inflammation and vascularpermeability

E I C O S A N O I D S A R E V I T A L R E G U L A T O R S - T H E Y C O N T R O L E V E R Y

C E L L A N D O R G A N I N T H E B O D Y . T H E I R F U N C T I O N S I N C L U D E :


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Eicosanoids

Prostaglandins

Leukotriene

Thromboxane

T H E R E A R E 3 M A J O R T Y P E S O F E I C O S A N O I D S :


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Prostaglandin

Prostaglandins are found in most tissues

and organs.

They are produced by almost all nucleatedcells.

They are autocrine and paracrine lipid

mediators that act upon platelets,endothelium, uterine and mast cells.


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Prostaglandin E series or PGE

dilate arterioles and capillaries to bringabout a drop in blood pressure

relax vascular smooth muscle open the bronchi of the lungs

enhance blood flow through the kidneys

increase urinary volume as well as theexcretion of sodium ion

cause contraction of gut muscle in humans

T H E P G E S E R I E S A R E K N O W N T O :


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Prostaglandin F series or PGF

cause venule vasoconstriction which

increases blood pressure

constrict the bronchi of the lungs produce contractions of the uterus

induced abortion or labor at term in some

instances

T H E P G F S E R I E S I S K N O W N T O :


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Leukotrienes

The Leukotrienes are most commonly found in theleukocytes, mast cells, platelets, and vasculartissue of the lung and heart.

They are produced by basophils and mast cells bybreakdown of the membrane phospholipids.

Leukotrienes are involved in several immune-mediated inflammatory reactions of anaphylaxis

and are constituents of substances originallycalled "slow-reacting substance of anaphylaxis."


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Leukotrienes

Leukotrienes are important mediators of

the inflammatory response and are more

potent than histamines in constrictingairways and promoting tissue edema

formation.

They also function in adherence and aschemotactic agents for phagocytes


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Leukotrienes

They contract smooth muscle,

Affect vascular permeability,

Strong attractants of polymorphonuclearleukocytes.

L E U K O T R I E N E S A R E K N O W N T O :


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Thromboxane

Thromboxane is a vasoconstrictor and a

potent hypertensive agent, and it facilitates

platelet aggregation. Thromboxane is named for its role in clot

formation (Thrombosis)


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Thromboxane

constricts blood vessels,

suppress cyclic AMP,

promotes platelet aggregation

T H R O M B O X A N E I S K N O W N T O :


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Thromboxane

Thromboxane occurs in two known forms:

TXA2, the active form

TXB2 the inactive


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TXA2

It is produced by activated platelets.

It stimulates activation of new platelets as

well as increases platelet aggregation. Thromboxane A2 is also a known

vasoconstrictor and is especially important

during tissue injury and inflammation.


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TXB2

Thromboxane B2 is an inactive

metabolite/product of thromboxane A2.

It itself is not involved in platelet activationand aggregation in case of a wound, but

its precursor, thromboxane A2, is.

biochem eicosanoids

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