Autocoids - histamine and antihistamine Flashcards
what is an autocoid
what is it formed by
what do they function as
self medicinal agent (greek word)
formed by the tissues on which they act
they function as local hormones
where is histamine found (high concentrations)
lungs, skin, gastrointestinal tract
At a cellular level where is histamine found
in mast cells and basophils
where does non mast cell histamine occur
in histaminoytes in the stomach and in histaminergic neurone in the brain
how is histamine formed?
formed from histidine by the action of histidine decarboxylase
where is histamine stored in mast cells and basophils
intracellular granules in complex with acidic protein
what is histamine released in response to
inflammatory and allergic stimuli
Draw a diagram to explain histamine release
and explain the steps
draw on whiteboard
in what conditions do we release histamine
Tissue injury - a physical or chemical agent which causes injury to the tissue or skin triggers release of histamine from mast cells
allergic reactions - exposure of an antigen to a previously sensitised individual can trigger allergic reactions through IgE antibody action
drugs and other foreign compounds - morphine, dextran, antimalarial drugs, penicillins trigger histamine release
How many histamine receptors are there
4 - H1, H2, H3, H4
Where do H1 receptors mediate effects on
smooth muscle, leads to vasodilation and increased vascular permeability
what does intradermal injection of histamine cause
H1 mediated reddening of the skin, accompanied by a wheal and surrounding flare (triple response)
intravenous injection of histamine leads to
similar symptoms of anaphylactic shock and allergic reactions
