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 antiinflammatory 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.