2.
Prostaglandins and related compounds are collectively known
as eicosanoids, they all contain 20C parent cyclopentane ring.
Discovered by Ulf Von Euler (1930), extracted from human
semen (prostate gland).
Produced & released by nearly all mammalian cells;(Except
RBCs)
Perform a variety of functions
Produced in minute amounts and are not stored.
Have a half-life of 5 minutes or less, hence they are destroyed
very rapidly in the body.
INTRODUCTION
4.
The structure of PG is based on 20C parent saturated acid
called “Prostanoic Acid”
STRUCTURE
All PGs are 20C fatty acids containing a cyclopentane
ring.
All PGs have:
-OH group at 15th position, some at 19th
trans double bond at 13th position
6.
Arachidonic acid (precursor for most of the
prostaglandins)
Arachidonic acid is released from membrane bound
phospholipids by phospholipase A2.
It occurs due to a specific stimuli by hormones
(epinephrine or bradykinin)
Oxidation & cyclization of arachidonic acid to PGG2
which is then converted to PGH2 by peroxidase.
BIOSYNTHESIS OF PROSTAGLANDINS
7.
PGH2 (immediate precursor for the synthesis of a
number of prostaglandins, including prostacyclins &
thromboxane)
This is known as cyclic pathway of arachidonic acid.
CONTD…
8.
Act as local hormones:
Regulation of blood pressure : PGE, PGA & PGl2 increased
blood flow and decreased peripheral resistance to lower the
blood pressure.
Inflammation: PGEI & PGE2 induce the symptoms of
inflammation (redness, swelling, edema etc.) due to arteriolar
vasodilation.
Reproduction: PGE2 & PGF2 are used for the medical
termination of pregnancy & induction of labor.
Regulation of gastric secretion: PGs stimulate pancreatic
secretion & increase the motility of intestine which often causes
diarrhea.
BIOCHEMICAL ACTIONS OF
PROSTAGLANDINS
9.
Influence on immune system: Macrophages secrete PGE
which decreases the immunological functions of B-& T-
lymphocytes.
Platelet Aggregation:
PGI2: Inhibit Aggregation (Released by endothelial cells)
PGE2 & TXA2: ( Promote Clotting Process)
CONTD…
10.
(NSAIDs)
Non-steroidal anti-inflammatory drugs
(NSAIDs), such as aspirin and derivatives
of ibuprofen, inhibit cyclooxygenase
activity of PGH2 Synthase.
• They inhibit formation of prostaglandins
involved in fever, pain, & inflammation.
Ibuprofen and related compounds block
the hydrophobic channel by which
arachidonate enters the cyclooxygenase
active site.
INHIBITOR(S)
CH
COOH
H3C
CH2
CH
CH3
H3C
Ibuprofen
12.
Aspirin acetylates a serine hydroxyl group near the active site,
preventing arachidonate binding.
The inhibition by aspirin is irreversible.
Anti inflammatory Drugs inhibit Eicosanoid Synthesis
13.
Yes aspirin-like drugs inhibited the formation of
prostaglandins , but it does have some side effects.
Aspirin is not recommended for patients with low risk of heart
attack or stroke or those having history of gastric ulcers or have
genetic problem like clotting such as Hemophilia.
Aspirin is not also recommended for babies and children
because it may cause Reye’s syndrome which involves life
threatening damage to both the liver and brain
CONCLUSION