Histamines Flashcards
where is histamine synthesized
Mast cells and basophils
Where is histamine stored
granules
How is histamine metabolized
Methylated, oxidized or conjugated and excreted
2 types of histamine releases from mast cells
Antigen mediated release and non-antigen mediated release
Describe antigen mediated release
Mast cells bind to IgEs. When they encounter an antigen, they undergo degranulation of mast cell and release histamine
Describe mechanism of mast cell degranulation
binding of IgE to FcER
binding of antigen to IgE antibodies
clustering of FcER receptors
Influx of Ca2+ via CRAC
How does binding of antigen to antibodies affect Ca2+
Causes an increase in cytoplasmic Ca2+
What are the two drugs that prevent histamine release
Cromolyn sodium
Nedocromil
H1 receptor location
Vascular endothelium
H1 receptor physiologic effects
Vasodilation (due to increase in NO)
Contraction of endothelial cells
Effect of NO in H1
Causes vasodilation, even though H1 causes constriction in endothelial cells
Where are H2 receptors found
Vascular muscle
H2 effect on vasculature
Vasodilation
Pathway of H1
Gq
pathway of H2
Gs
effects of histamine on CVS
Heart- moderate increase in force and rate of contraction (mediated by h2 causes increase in SA conduction)
vasodilation- H1 in endothelium
H2 in smooth muscle
Effects of histamine on respiratory
H1 mediated constriction of bronchial smooth muscle
What class does chloromphenamine belong to? structure?
Alkylamines, Two carbons attatched to nitrogen
What class does diphenhydramine belong to? structure?
Instead of just two carbons and an amine, Oxygen is added before carbons
What class does pyrilamine belong to? structure
Ethylene diamines. Instead of an O, we have two nitrogens on either side of the carbons
What class does promethazine belong to? structure?
Phenothiazine, has sulfur
What class does cyproheptadine belong to?
piperadines. Six member ring with an N
What class does hydroxyzine belong to? structure?
Two N in six member ring
Name the 4 2nd gen antihistamines
Loratidine (claratin)
allegra (fexofenadine)
deslovatidine(clarinex)
etrizine (zyrtec)
role of fluticasone and budesonide in treating allergic rhinitis
Slow onset, slow absorption, treats allergic rhinitis
