| Question |
 |
|
| Answer |
|
|
| How are eicosanoids different from steroid hormones? |
act locally, created then quickly destroyed |
| What do eicosanoids mediate? |
inflammatory response, fever, pain, gastric integrity, blood clotting |
| What physiologic responses do eicosanoids control? |
vasodilation & constriction, platelet aggregation & inhibition, smooth muscle contraction & relaxation |
| What is the precursor for eicosanoids? |
arachidonic acid |
| Where is arachidonic acid stored? |
membrane phospholipids |
| What are the 3 types of eicosanoids? |
prostaglandins, thromboxanes, and leukotrienes |
| What is the precursor for arachidonic acid? |
linoleic acid (essential fatty acid) |
| What regulates amount of eicosanoids? |
phospholipase A2 |
| What enzyme converts arachidonic acid to leukotrienes? |
lipoxygenases |
| What enzyme converts arachidonic acid to prostaglandins & thromboxanes? |
Cox 1 & 2 (cyclooxygenases) followed by cell specific synthases |
| Leukotriene synthesis involves what key intermediate? |
5-HPETE |
| Besides leukocytes, what cell is involved in leukotriene synthesis? |
platelets |
| What 2 signaling mechanisms do eicosanoids use? |
autocrine & paracrine |
| Which eicosanoid mediates inflammation, fever, plateletaggregation and disaggretation,induce labor, maintain stomach lining? |
prostaglandins |
| Which eicosanoid is produced by platelets, promoteaggregation (blood clotting) andvasoconstriction |
thromboxanes |
| Which eicosanoid is produced by mast cells, mediate allergic reactions; SlowReacting Substance of Anaphylaxis(SRS-A), 104X potent than histamineProduced in plasma - smooth musclecell contraction |
leukocytes |
| Which enzyme is blocked by cortisol/anit-inflammatories? |
Phopsholipase A2 |
| Wich enzyme is blocked by NSAIDS? |
COX 1 & 2 |
| Which enzyme is blocked by anti-asthmatics? |
lipoxygenases |
| Why is aspirin imperfect? |
It blocks cox 1 & 2, but cox 1 protects stomach lining via PGE2 |
| What are the drawbacks to COX2 inhibition? |
Since COX2 (PGI2) inhibits platelet aggregation while COX 1 activates it (TGA2), Inhibiting COX 2 can lead to excess clotting |
| How does aspirin prevent heart attacks? |
By covalently modifying COX 1 & 2, aspirin leads to their degradation. Since platelets cannot create new cox 1 & 2, this = anticoagulation (however - not all platelets impacted, so some clotting still occurs) |
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