MEMBRANES AND RECEPTORS

Looking at the classical receptor, usually the drug will interact with the cell membrane…

ie. Epinephrine


Drug receptors are proteins, often embedded within cell membranes. Membrane-bound proteins are inserted within the lipid bilayer (many have catalytic functions or are enzymes), and are often stabilized by polysaccharide chains on the cell surface, which gives greater stability to the protein.


Classical receptors’ binding sites are specific for specific extracellular endogenous transmitters which then illicit some effect.


An example of a non-classical receptor system:

Dihydrofolate reductase is an enzyme involved in cell proliferation. Some cancer cells are inhibited if dihydrofolate reductase is inhibited by a drug called methotrexate. When methotrexate is bound to the enzyme, the dihydrofolate reductase enzyme is inactivated .. THIS IS NOT A CLASSICAL RECEPTOR SYSTEM, because dihydrofolate reductase is NOT bound to a cell membrane, but is an intracellular enzyme… so methotrexate must enter the cell and find dihydrofolate reductase. Thus, we are now expanding beyond our classical theory, and pharmacology is in a period of transition beyond what we would call classical receptor theories. So we are continually redefining our understanding of receptors.

Category: Pharmacology Notes