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Biochem Block 6
Prostaglandins Block 6
Question | Answer |
---|---|
Three related compounds that are considered eicosanoids? | prostaglandins, leukotrienes, thromboxanes |
Where are eicosaniods (ie. prostaglandins)made? | synthesized in all cells |
How do eicosanoids act? How long? | act locally with very short half-life |
What quantity is needed to elicit a reaction? | very small concentration for desired effect |
What eicosanoid do platelets synthesize? Why? | thromboxane; TXA2, promotes platelet aggregation and local vasoconstriction |
What eicosanoid do vascular endothelial cells synthesize? Why? | prostacylin; PGI2, inhibits platlet aggregation and stimulates vasodilation |
What are the two eicosanoids with opposing actions? From what cells? | thrombaxane from platelets vs. prostacylin from vascular endothelial cells |
Thromboxane causes what reactions? | platelet aggregation vasoconstriction |
Prostacylin causes what reactions? | platelet dispersion vasodilation |
Which type eicosanoid does aspirin affect? | suicide inhibitor for thromboxane - with no nucleus the platelets cannot make more of it. |
What is the most common precursor of prostaglandins? | arachidonic acid |
What is the dietary precursor of a prostaglandin? | linoleic acid |
Where does arachidonic acid come from? | released from membrane-bound phospholipids by phospholipase A2 |
The important enzyme for leukotriene creation | lipoxygenase |
the important enzyme for prostacylin and thromboxanes? | cyclo-oxygenase |
The two enzymes Luchia want you to know regarding prostaglandin production | phospholipase A2 cyclo-oxygenase |
The two important anti-inflammatory drugs that inhibit prostagladins? | steriodal drugs (glucocorticoids) & NSID |
What do glucocorticoids inhibit? | phospholipase A2, thus prevent production of arachidonic acid |
What do Aspirin and other non-steroidal anti-inflammatory drugs inhibit? | cyclooxygenase, thus preventing PGH2 |
What is PGH2? What is the 2? | Prostaglandin endoperoxide - the two indicates where the double bond is located |
Where does glucocorticoid regulation of inflammation reactions (such as asthma attack) occur? | It is steriod - so in nucleus!!! down regulates expression of phospholipase A2 gene |
What is the difference between COX1 and COX2 isozymes? | COX 1 is made constantly in most tissue COX 2 is inducible in a limited tissues |
What is the role of COX1? | maintenance of healthy gastric tissue, renal homeostasis, platelet aggregation |
What is role of COX2? | activated in immune response and inflammation; causes the pain, heat, redness, swelling, and fever. My COX does 2 |
How does aspirin work against COX1 & COX2? | Non Competitive and Non-selective acetylation: irreverisibly inactivates it |
Why does low dose aspirin therapy work? | platelets have life span of 7-10 days, when taken daily aspirin affects them as they are made. |
What effect does aspirin have on vascular endothelial cells? | It mildly minimizes prostacyclin, but the nucleated cells can make more! |
What effect is created by low dose aspirin therapy? | mild defect in hemostasis, or blood clotting. Prevents the thrombus formation in area of atherosclerotic plaque |
Specific area low dose aspirin helps in the vascular tree | coronary arteries |
What is the basis of aspirins and other NSID's toxicity? | systemic inhibition of COX-1 with damage to stomach, kidneys and impaired clotting |
What is the problem with the COX-2 inhibitors | linked to increase in heart attacks |
What does COX-2 do in the body when over produced, such as chronic insult | up-regulates cytokines, endotoxin, growth factors and tumor promotors. |
In healthy endothelium, prostacylin is released into the blood. What effect does this have | plasma prostacyclin binds to receptors activating cAMP. cAMP inhibits release of granules with platlet aggregating agents |
What are platelet aggregating agents | ADP + Serotonin |
TXA2 promotes what 4 things | 1. vasoconstriction 2. platelet aggregation 3. mobilizes intracellular calcium 4. contraction of smooth muscle |
PGI2 promotes what 2 things | 1. vasodilation 2. inhibits platelet aggregation |
Bonus question: PGF2(alpha) does what | smooth muscle contraction stimulate uterine contraction |
Bonus question:PGE2 does what | vasodilation relaxes smooth muscle used to induce labor |
Why would the body secrete TXA2 and PGI2 at the same time? | limits the formation of thrombi to the sight of injury |
If you have asthma what eicosanoids are causing you trouble? | Leukotrienes |
What forms leukotrienes from arachinic acid? | arachidonic acid catalyzed by 5-lipoxygenase to 5-HPETE. This forms different leukotrienes depending on the tissue |
How does aspirin therapy help asthmatics? | It does not help. Must use steriods |