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Questions and Answers
Which of the following enzymes is responsible for the conversion of arachidonic acid into leukotrienes?
Which of the following enzymes is responsible for the conversion of arachidonic acid into leukotrienes?
- Cyclooxygenase (COX)
- Lipoxygenase (correct)
- Phospholipase A2
- Prostaglandin synthase
Which of the following eicosanoids is known to cause potent bronchoconstriction and chemoattraction of leukocytes?
Which of the following eicosanoids is known to cause potent bronchoconstriction and chemoattraction of leukocytes?
- LTB4 (correct)
- TXA2
- PGE2
- PGI2
Which of the following therapeutic effects is associated with PGE1?
Which of the following therapeutic effects is associated with PGE1?
- Treatment of erectile dysfunction (correct)
- Prevention of platelet aggregation
- Induction of abortion
- Treatment of open-angle glaucoma
What is the primary mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs)?
What is the primary mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs)?
Which prostanoid receptor type corresponds to the receptor that binds to PGD2?
Which prostanoid receptor type corresponds to the receptor that binds to PGD2?
A drug that selectively inhibits COX-2 would primarily target which of the following processes?
A drug that selectively inhibits COX-2 would primarily target which of the following processes?
Which of the following best describes the action of PGF2α?
Which of the following best describes the action of PGF2α?
What is the effect of thromboxane A2 (TXA2) on platelets?
What is the effect of thromboxane A2 (TXA2) on platelets?
How do corticosteroids inhibit the synthesis of eicosanoids?
How do corticosteroids inhibit the synthesis of eicosanoids?
A patient is prescribed misoprostol. What is the drug's mechanism of action, and what condition is it used to treat?
A patient is prescribed misoprostol. What is the drug's mechanism of action, and what condition is it used to treat?
Which of the following is a therapeutic use of prostacyclin (PGI2)?
Which of the following is a therapeutic use of prostacyclin (PGI2)?
What is the role of cyclooxygenase-1 (COX-1) in the body?
What is the role of cyclooxygenase-1 (COX-1) in the body?
Which of the following effects is associated with leukotrienes in the respiratory system?
Which of the following effects is associated with leukotrienes in the respiratory system?
Which eicosanoid is used to maintain vasodilation and patency of the ductus arteriosus in infants undergoing surgery for congenital great vessel transposition?
Which eicosanoid is used to maintain vasodilation and patency of the ductus arteriosus in infants undergoing surgery for congenital great vessel transposition?
What is the mechanism by which latanoprost eye drops reduce intraocular pressure in open-angle glaucoma?
What is the mechanism by which latanoprost eye drops reduce intraocular pressure in open-angle glaucoma?
Which of the following best describes the role of arachidonic acid in the synthesis of eicosanoids?
Which of the following best describes the role of arachidonic acid in the synthesis of eicosanoids?
What is the effect of prostaglandins on the hypothalamus in relation to fever?
What is the effect of prostaglandins on the hypothalamus in relation to fever?
Which of the following is the primary mechanism of action of Enzaprost?
Which of the following is the primary mechanism of action of Enzaprost?
Why are selective COX-2 inhibitors preferred over non-selective NSAIDs in some patients?
Why are selective COX-2 inhibitors preferred over non-selective NSAIDs in some patients?
The mixture of LTC4, LTD4, and LTE4 is referred to as the slow-reacting substance of anaphylaxis (SRS-A). What is the primary effect of SRS-A?
The mixture of LTC4, LTD4, and LTE4 is referred to as the slow-reacting substance of anaphylaxis (SRS-A). What is the primary effect of SRS-A?
What is the primary mechanism by which corticosteroids reduce inflammation?
What is the primary mechanism by which corticosteroids reduce inflammation?
Which of the following scenarios would most warrant the use of a selective COX-2 inhibitor over a non-selective NSAID?
Which of the following scenarios would most warrant the use of a selective COX-2 inhibitor over a non-selective NSAID?
A patient is undergoing cardiopulmonary bypass surgery. Which prostaglandin analog would be most beneficial during this procedure, and why?
A patient is undergoing cardiopulmonary bypass surgery. Which prostaglandin analog would be most beneficial during this procedure, and why?
In the context of eicosanoid synthesis, what is the most critical role of cyclooxygenase (COX) enzymes?
In the context of eicosanoid synthesis, what is the most critical role of cyclooxygenase (COX) enzymes?
What is the primary reason that thromboxanes and leukotrienes have limited clinical applications despite their potent biological activities?
What is the primary reason that thromboxanes and leukotrienes have limited clinical applications despite their potent biological activities?
A researcher is investigating the effects of a novel compound on uterine contractility. Which prostaglandin receptor subtype is most likely to mediate the contractile effects in the uterus?
A researcher is investigating the effects of a novel compound on uterine contractility. Which prostaglandin receptor subtype is most likely to mediate the contractile effects in the uterus?
In the biosynthesis of eicosanoids, what is the immediate precursor to prostaglandins, thromboxanes, and prostacyclin?
In the biosynthesis of eicosanoids, what is the immediate precursor to prostaglandins, thromboxanes, and prostacyclin?
A patient with asthma experiences a severe allergic reaction leading to bronchoconstriction and airway inflammation. Which group of eicosanoids is most directly responsible for these symptoms?
A patient with asthma experiences a severe allergic reaction leading to bronchoconstriction and airway inflammation. Which group of eicosanoids is most directly responsible for these symptoms?
What is the rationale for using prostaglandin analogs like misoprostol in the treatment of peptic ulcers?
What is the rationale for using prostaglandin analogs like misoprostol in the treatment of peptic ulcers?
A researcher aims to study the effects of different eicosanoids on vascular smooth muscle contraction. Which specific eicosanoid and receptor interaction should they target to induce vasoconstriction?
A researcher aims to study the effects of different eicosanoids on vascular smooth muscle contraction. Which specific eicosanoid and receptor interaction should they target to induce vasoconstriction?
A newborn infant presents with a congenital heart defect requiring maintenance of the ductus arteriosus patency prior to surgery. Which prostaglandin is most appropriate to administer, and what is its mechanism of action in this context?
A newborn infant presents with a congenital heart defect requiring maintenance of the ductus arteriosus patency prior to surgery. Which prostaglandin is most appropriate to administer, and what is its mechanism of action in this context?
A patient with glaucoma is prescribed latanoprost eye drops. What is the primary mechanism by which this medication reduces intraocular pressure?
A patient with glaucoma is prescribed latanoprost eye drops. What is the primary mechanism by which this medication reduces intraocular pressure?
Which eicosanoid is primarily responsible for promoting platelet aggregation, and through which receptor does it exert this effect?
Which eicosanoid is primarily responsible for promoting platelet aggregation, and through which receptor does it exert this effect?
In the context of inflammation, what is the role of LTB4?
In the context of inflammation, what is the role of LTB4?
A patient is prescribed dinoprostone to induce labor. What is the mechanism of action of this drug?
A patient is prescribed dinoprostone to induce labor. What is the mechanism of action of this drug?
After an injury, a patient's inflammatory response leads to localized pain and fever. Which of the following eicosanoids is most directly involved in the development of fever?
After an injury, a patient's inflammatory response leads to localized pain and fever. Which of the following eicosanoids is most directly involved in the development of fever?
In the context of renal physiology, how do prostaglandins generally affect renal blood flow (RBF) and water excretion?
In the context of renal physiology, how do prostaglandins generally affect renal blood flow (RBF) and water excretion?
A patient is diagnosed with peripheral vascular disease and requires a medication to prevent platelet aggregation. Which prostaglandin analog is most suitable for this purpose?
A patient is diagnosed with peripheral vascular disease and requires a medication to prevent platelet aggregation. Which prostaglandin analog is most suitable for this purpose?
Concerning the mechanism of action, how do non-selective NSAIDs reduce pain and inflammation?
Concerning the mechanism of action, how do non-selective NSAIDs reduce pain and inflammation?
Which of the following best describes the role of phospholipase A2 in the synthesis of eicosanoids?
Which of the following best describes the role of phospholipase A2 in the synthesis of eicosanoids?
Flashcards
Eicosanoids
Eicosanoids
A class of compounds derived from arachidonic acid. Includes prostaglandins, thromboxanes, and leukotrienes.
Phospholipase A2
Phospholipase A2
Enzyme that acts on phospholipids to release arachidonic acid
Cyclooxygenases (COX)
Cyclooxygenases (COX)
Enzymes that convert arachidonic acid into prostaglandin H2 (PGH2).
PGI2 effects
PGI2 effects
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TXA2
TXA2
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Leukotrienes
Leukotrienes
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LTB4 function
LTB4 function
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Corticosteroids
Corticosteroids
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NSAIDs
NSAIDs
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Alprostadil action
Alprostadil action
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PGE1 use in infants
PGE1 use in infants
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Dinoprostone
Dinoprostone
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Prostacyclin action
Prostacyclin action
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Latanoprost action
Latanoprost action
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COX-1 function
COX-1 function
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COX-2 function
COX-2 function
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Eicosanoid Synthesis
Eicosanoid Synthesis
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COX-1
COX-1
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Misoprostol
Misoprostol
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Classical NSAIDs
Classical NSAIDs
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Fever
Fever
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PGE1
PGE1
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Study Notes
Eicosanoid Biosynthesis
- Eicosanoids are synthesized from arachidonic acid, which is released from phospholipids by phospholipase A2.
- A stimulus is required for this synthesis.
- Arachidonic acid is then acted upon by either cyclooxygenase (COX-1 and COX-2) to produce PGH2 or by lipoxygenases to produce 12-HETE, 15-HETE, and Leukotrienes (LTs).
- PGH2 is a precursor to various prostaglandins (PGD2, PGE2, PGF2α, PGI2, and TXA2).
Classes of Eicosanoids
- The classes include Prostaglandins (PGs), Thromboxane A2 (TXA2), and Leukotrienes (LTs).
Mechanism of Action
- PGs and other eicosanoids act on cell surface seven-transmembrane receptors (G-protein coupled receptors).
- These receptors are termed DP1-2, EP1-4, FP, IP, and TP.
- Each corresponds to the receptor that binds a specific PG (e.g., DP1-2 receptors bind to PGD2).
Effects of Eicosanoids
- PGE1 and PGE2 cause vasodilation.
- PGE1 and PGE2 cause edema (+).
- PGE1 and PGE2 cause relaxation of the bronchi.
- PGE1 and PGE2 affect the uterus, causing the pregnant uterus to contract and non-pregnant uterus to relax.
- PGE1 and PGE2 increase renal blood flow (RBF) and water excretion in the kidney.
- PGE1 and PGE2 decrease gastric HCl and increase gastric mucus secretion in the stomach.
- PGE1 and PGE2 cause fever in the hypothalamus.
- PGI2 causes vasodilation.
- PGI2 inhibits platelet aggregation.
- PGF2α causes vasoconstriction.
- PGF2α causes constriction of the bronchi.
- PGF2α causes contraction of the uterus.
- PGF2α decreases renal blood flow (RBF) in the kidney.
- TXA2 causes vasoconstriction.
- TXA2 increases platelet aggregation.
- LTB4 causes vasodilation.
- LTB4 causes edema (+++).
- LTB4 causes potent constriction of the bronchi.
- LTB4 causes chemotaxis
- Fever is defined as resetting the thermostat of heat regulating center to a high temperature.
Therapeutic Uses of Prostaglandins
- PGE1 can be used for the treatment of erectile dysfunction in men, promoting smooth muscle relaxation of the corpus cavernosum (Alprostadil).
- PGE1 can be used before and during surgery of congenital great vessels transposition in infants, maintaining vasodilation (VD) and patency of ductus arteriosus and pulmonary vascular bed and preventing hypoxia (Alprostadil).
- PGE1 can be used for the treatment of peptic ulcers, decreasing HCl and increasing gastric mucus secretion (Misoprostol).
- PGE2 can be used for the induction of abortion and facilitation of labor, stimulating uterine contractions (Dinoprostone).
- PGE2 can be used for the treatment of peripheral vascular disease.
- PGI2 (Prostacyclin) can be used for thrombotic disorders, cardiopulmonary bypass surgery, hemodialysis, and retinal artery occlusion, preventing platelet aggregation (Prostacyclin).
- PGI2 (Prostacyclin) can be used for the treatment of pulmonary hypertension and peripheral vascular disease.
- PGF2α can be used for the induction of abortion and facilitation of labor (Enzaprost).
- PGF2α can be used for the treatment of open-angle glaucoma, enhancing uveoscleral outflow of aqueous humor (Latanoprost eye drops).
Leukotrienes
- Leukotrienes are derived from arachidonic acid by the action of lipoxygenase enzyme.
- The four main types of leukotrienes are LTB4, LTC4, LTD4, and LTE4.
- A mixture of LTC4, LTD4, and LTE4 is termed the slow-reacting substance of anaphylaxis (SRS-A) that is released during an inflammatory response.
- LTB4 is a powerful bronchoconstrictor and chemotactic for leukocytes.
Clinical Uses of Thromboxanes and Leukotrienes
- Thromboxanes and leukotrienes have no current clinical uses.
Inhibitors of Eicosanoid Synthesis
- Corticosteroids inhibit phospholipase A2 enzyme and decrease the synthesis of all the eicosanoid family.
- Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) inhibit cyclooxygenase enzyme.
- Classical NSAIDs (e.g., aspirin and ibuprofen) inhibit both COX-1 and COX-2 non-selectively.
- NSAIDs (e.g., celecoxib) selectively inhibit COX-2 enzyme that is induced during inflammation.
- Leukotriene inhibitors are another class of inhibitors.
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