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Flashcards in Eicosanoids Deck (36):
1

Eicosanoids are important bio-active agents synthesized form what?

PUFAs - 20 carbons long

2

Prostanoids are synthesized by the ___ pathway

cyclooxygenase (COX)

3

The leukotrienes and lipoxins are synthesized by the ____ pathway

lipoxygenase

4

Both the COX pathway and the lipoxygenase pathway start with a 20 carbon PUFA, usually ____ acid

arachidonic

5

The arachidonic acid is derived from membrane ____. It is released by the action of ____ ___

phospholipid; phospholipase A2

6

What is the rate-limiting step in prostaglandin synthesis?

hydrolysis of arachidonic acid

7

Agents which stimulate the production of prostaglandins do so by stimulating the activity of what?

phospholipase A2

8

The other C20 PUFAs may serve as precursors. EPA (C20:5) is obtained from what? It is a w-__ acid

diet; 3

9

PGH2 is the first prostaglandin product and is the common intermediate of what?

1. the other important prostaglandins
2. the thromboxanes

10

Prostaglandin synthase (PGS) has two components: cylclooxygenase (COX) and PG hydroperoxidase. What do these two components catalyze?

1. COX: catalyzes synthesis of PGG2
2. PG hydroperoxidase catalyzes the formation of PGH2 from PGG2

11

PG hydroperoxidase requires what?

GSH

12

The number of double bonds in the side chains depends on the PUFA precursor. IF the precursor is eicosatrienoic acid, the product would be ____. If the precursor is eicosapentaenoic acid, the product would be ___.

PGH1; PGH3

13

There are two forms of COX. COX1 is a ____ enzyme found where?

constitutive; found in gastric mucosa, platelets, vascular endothelium and kidney

14

There are two forms of COX. COX2 is a ___ enzyme found where?

inducible; found in activated macrophages and monocytes which have been stimulated by PAF, IL-1, or LPS; also found in smooth muscle cells, epithelial cells and neurons

15

COX2 induction is inhibited by ____

glucocorticoids

16

The ____ inhibit COX.
ex: aspirin, ibuprofen etc.

NSAIDS

17

Aspirin inhibits COX__ more than COX__

2; 1

18

Aspirin's mechanism of action involves ___ of the COX enzyme

acetylation

19

Steroid anti-inflammatory drugs (hydrocortisone, prednisone) act by inhibiting this enzyme's activity.

phospholipase A2

20

PGE2 and PGF2 are major prostaglandins produced where?

kidney and spleen

21

PGE2 is produced by what?

macrophages, mast cells, and B cells

22

PGD2 is produced by ___ cells

mast

23

PGI2 and PGF2 are major prostaglandins produced by ___ ___

blood vessels

note: PGI2 is an important inhibitor of platelet aggregation

24

Thromboxane A2 (TXA2) is a major prostaglandin produced by ____

platelets

note: stimulates platelet aggregation

25

The half-life of TXA2 is very long. True or false?

False; very short - it is rapidly converted to the inactive TXB2

26

In what 3 ways do prostaglandins mediate inflammation?

1. induce redness and heat
2. increase capillary permeability
3. pyrogens activate synthesis of prostaglandins

27

Prostaglandins stimulate ____ contraction and inhibit ____ acid secretion

uterine; gastric

28

HPETEs are highly reactive intermediates that are rapidly converted to their analogous _____ acids or to ____

HETEs; leukotrienes

29

The most important products of lipoxygenases in humans is ____-____ since these are converted into the leukotrienes

5-HPETE

30

Leukotrienes are important secretory products of ____ and each one contains a conjugated ___ group

leukocytes; trienoic

note: the subscript number refers to the total number of double bonds

31

Leukotrienes mediate ____ disorders

inflammatory

32

SRS-A is a mixture of LTC4, LTD4, and LTE4 and is a potent stimulator of the ___ ___ musculature

bronchial airway

33

LTB4, LTC4, LTD4, and LTE4 increase ___ ___

vascular permeability

34

inhibition of angiogenesis, clearance of pulmonary edema, and protection of reperfusion injury are all actions of what?

lipoxins

35

Current drugs for ___ include 5-LOX inhibitors, and LT-receptor antagonists

asthma

36

Eicosanoids act via a __ trans-membrane __ ___ coupled receptor

7; G protein