Eicosanoids

Question 1

Enzyme that catalyzes the formation of histamine

Answer 1

Histidine-decarboxylase catalyzes the formation of histamine from L-histidine

Question 2

Where is histamine-decarboxylase located

Answer 2

• Mast cells, basophils, cells of the epidermis, cells in the gastric mucosa, neurons, cells of rapidly growing tissues (especially certain tumors)

Question 3

H1 receptor acts via

Answer 3

Gq: increases IP3 and DAG

Question 4

H2 receptor acts via

Answer 4

Gs: increases cAMP

Question 5

H3 receptor acts via

Answer 5

Gi: decreases cAMP

Question 6

H4 receptor acts via

Answer 6

Gi: decreases cAMP

Question 7

H1 receptor is predominantly found in _______ where it ____

Answer 7

1. blood vessels
2. ➢ vasodilation: decreases BP (via NO release)
   ➢ Bronchoconstriction (features of anaphylaxis)

Question 8

H2 receptor is predominantly found in _______ where it ____

Answer 8

stomach

2. stimulates gastric secretion

Question 9

H3 receptor is predominantly found in _______

Answer 9

presynaptic: brain, myenteric plexus, other neurons

Question 10

H4 receptor is predominantly found in _______

Answer 10

Eosinophils. neutrophils, CD4 T-cells

Question 11

Histamine Release Inhibitors

Answer 11

• Beta2-adrenoceptor agonists
• Theophylline
• Cromolyn sodium and nedocromil
• Glucocorticoids (IgE-dependent release)

Question 12

physiologic antagonists

Answer 12

Epinephrine (hence used in anaphylactic shock)

Question 13

Receptor antagonists

Answer 13

• H1 receptor antagonists (antihistamines)

* H2 receptor antagonists