Describe the basic mechanism of drug receptors and the four mechanisms for transmembrane signaling which are well understood.
Most drug receptors are proteins,or polypeptides, whose shape and electric charge provide a match to a drug's corresponding chemical shape or charge. Drug receptor proteins include receptors on cell surfaces and within the cell.
Lipid-soluble drugs cross the cell membrane and act on intracellular receptors, to initiate the drug response. Ex-Corticosteroids,vitamin D, thyroid hormone
Intracellular Receptor Activation -The drug attaches to the extracellular portion of a protein receptor, which projects into the cell cytoplasm (transmembrane protein) and activates an enzyme system, such as tyrosine kinase, in the intracellular portion to initiate and effect. Ex- Insulin, platelet-derived growth factor PDGF
Drug-regulated Ion channels-The drug attaches to a surface receptor, which regulates the opening of an ion channel. Ex-Acetylcholine receptors on skeletal muscle, y-aminobutyric acid GABA
Receptors linked to G proteins-The drug attaches to a transmembrane receptor that is coupled to an intracellular enzyme by a G protein (guanine nucleotide-regulating protein). Ex- B-adrenergic agents, acetylcholine at paracsympathetic nerve endings