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Flashcards in Prostaglandins Deck (48):
1

Eicosanoids

enzyme derived products of arachadonic acid

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eicosanoids catalyzed by cyclooxygenase

Prostanoids

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five types of prostanoids

PGD2, PGE1/2, PGF2a, PGI2, TXA2

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isoeicosanoids

free radical catalyzed products of AA

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arachadonic acid (AA)

one of the fatty acids that makes up the phospholipid bilayer

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phospholipase A2 (PLA2)

required for the release of AA from cell membranes

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role of COX in AA pathway

converts free AA to an intermediary compound that is rapidly converted by isomerases and syntheses into prostanoids

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what enzyme converts intermediate into TxA2?

thromboxane synthase (in platelets)

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what enzyme converts intermediate into PGE2?

PGE2 isomerase (in GI endothelial cells)

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what enzyme converts intermediate to PGI2?

PGI2 isomerase (in vascular endothelial cells)

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activation of PLA2

by diverse stimuli such as inflammation, chemical, and physical stimuli

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two forms of PLA2

cytosolic and inducible

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cytosolic PLA2

constitutive, present in concentrations high enough for regulatory functions of the cell.

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inducible PLA2

activated in setting of inflammation or cancer. responsible for greater proportion of free AA in these conditions

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isoforms of COX

COX1 (constitutively) and COX2 (inducible)

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expression of COX1

constitutive. but does contribute some degree of prostanoid formation during inflammation

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expression of COX2

expressed in times of inflammation and cancer

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function of COX1

housekeeping functions: cytoprotective in GI, platelet function

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what cells only express COX1?

platelets

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tissue distribution of COX1

broad distribution

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what induces COX2 up regulation?

inflammatory stimuli, cytokines, growth factor, tumor promoters

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COX2 is the predominant isoform in what cells?

endothelial cells

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distribution of COX2

kidney, brain, synovial cells, macrophages, monocytes

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what down regulates COX2

glucocorticoid

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cellular mechanism of action of prostanoids

GPCR binding specific to prostaglandin activates second messenger system

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catabolism of prostanoids

made quickly and degraded quickly. use as drugs is therefore limited unless made into stable analogs

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what cells produce TxA2

platelets, macrophages, kidney parenchymal cells

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COX isoform responsible for TxA2

COX1

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TxA2 activity

induces platelet aggregation, vasoconstriction and smooth muscle cell proliferation

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where is prostacyclin I2 (PGI2) produced?

endothelial cells

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COX isoform for PGI2

COX2

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activity of PGI2

inhibits platelet aggregation and smooth muscle cell proliferation, vasodilates, proinflammatory

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role of prostaglandin E (PGE1/2)

cytoprotection in the GI by inhibition of gastric acid secretion (COX1), regulates renal blood flow via vasodilation (COX2), regulates salt via renin (COX2), induces uterine/GI smooth muscle contraction (COX1/2), cryogenic role for body temp (COX1/2), pro inflammatory effects (COX2)

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role of prostaglandin F2a (PGF2a)

induces vascular smooth muscle and uterine contraction (luteal regression), vasoconstriction (COX1/2)

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role of PGD2

cutaneous dilation, inhibits platelet aggregation, promotes sleep, mast cell product, chemotaxis of Th2, hair follicles

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role of inflammation in prostanoid release

increases sPLA2, which increases AA release, which increases prostanoid production via increased COX2 expression

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prostanoids involved in dolor

nocioception: PGE1/2, PGI2

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prostanoids involved in rubor

vasodilation: PGE1/2, PGI2

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prostanoids involved in calor

fever: PGE1/2

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prostanoids involved in tumor

vasodilation, edema, leukocyte infiltration, chemotaxis: PGI2, PGE2, PGD

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steroids

reduce the release ofAA from cell membrane by targeting PLA2

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NSAIDs

reduce the production of intermediary compounds by targeting COX

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Ridogrel

reduces production of TxA2 by targeting thromboxane synthase

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antagonist to prostanoid

none known

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carbaprost

PGF2 analog used as abortifacient, post-partum bleeding to expel placenta

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misoprostol

PGE analogue used as abortifacient and for gastric cytoprotection

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dinoprostone

PGE analogue used to induce labor

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treatment for PDA

PGE analog