Medical Definition of Down-regulation
1.
Development of a refractory or tolerant state consequent upon repeated administration of a pharmacologically or physiologically active substance.
It is the process that decreases ligand and receptor interactions or reduces the responsiveness of a cell to a stimulus following first exposure.
This is often accompanied by an initial decrease in affinity of receptors for the agent and a subsequent reduction in the number of available receptors expressed on the surface which can result from internalisation of the ligand:receptor complex or from decreased expression of the receptor.
Classically the concept referred to hormone receptors but contemporary usage includes other cell surface receptors.
(03 Jul 1999)
Lexicographical Neighbors of Down-regulation
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