PROSTAGLANDINS

PROSTAGLANDIS Definition They are the group of closely related biologically active lipids. they are the derivatives of polygenic fatty acid. Known as prostanoic acid. they are like hormones, in that they act as chemical messengers, but do not move to other sites, but work within the cell where they are synthesized.

BIOLOGICAL FUNCTION 1.They act as mediators in the inflammatory response, particularly involving the joints (rheumatoid arthritis), skin (psoriasis) and eyes. 2.In pain and fever. 3.Regulation of blood pressure. 4.Relexation & contraction of uterine muscles. 5.The regulation of sleep/wake cycle.

Chemical structure All are the derivatives of 20 carbon fatty acid prostanoic acid, in which carbon atoms 8 to 12 is a cyclopentane ring. PG are unsaturated carboxylic acids consisting of a 20 carbon skeleton that also contain a 5 member ring. They are biochemically synthesized from the fatty acid called ARACHDONIC ACID’’. (5,8,11,14 eicosenoic acid). OR (eicosatetraenoic acid).

Chemical structure

PROSTANOIC ACID PGS are synthesized by cyclization of centre of carbon chain of arachidonic acid forming a cyclopentane ring. Variation in double bonds, OH and keto gps gives rise to several type of PGs. Arachidonic acid is a polyunsaturated fatty acid that has 4 double bonds. The double bond at g4 is the sixth carbon atoms from the terminal CH3 group. Thus making arachidonic acid .

Classification They are classified into 2 main groups: 2. Leukotrienes 1.Prostanoids a. Prostaglandins b. Prostacycline c. Tromboxanes.

Prostaglandins PGS are further classified into 4 main classes. 1.PGE:- PGE-1, PGE-2, PGE-3, 2. PGF:- PGF-1, PGF-2, PGF-3. 3.PGA:- PGA-1, PGA-2, 19-OH PGA-1&2 4.PGB:- PGB-1, PGB-2, 19-OH PGB1&2.

Similarities in structure All the 4 type of PGs have OH group at C15 and a trans double bonds at C13

DIFFERENCE Difference occurs in the cyclopentane ring by variation in double bonds, OH &Keto group in the 5-membered ring.

PHERMACOLOGICAL FUNCTION OF PGS:- Its involved in the relief of asthma and nasal congestion. Prevention of gastro intestinal ulcer.

Formation of prostacyclin & Thromboxane Prostaglandins Serve as precursors for the synthesis of Thromboxane & prostacyclins. (structure is related to prostanoic acid). Prostacyclins are synthesized by the action of prostacyclin synthetase enzyme. While Thromboxanes are synthesized by Thromboxane synthetase enzyme found is Thromboxane (platelets)and act as a potent platelets aggregating factor. The synthesis of PG, prostacyclins & Thromboxane can be blocked by the use of steroids or non-steroidal anti-inflammatory drugs (NSAID), SUCH AS ASPIRIN which inhibits the enzyme endoperoxide synthetase which converts arachidonic acid prostaglandins.

Leucotrienes Arachidonic acid is oxidized at 5, 12 or 15 to form hydroproxi eicosatetraenoic acid. Leucotrienes are synthesized by WBC & mast cells. T-lymphocytes involved in allergic reaction.

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