Chapter 3 – Measurement and Expression of Drug Effects

Publisher Summary The biological activity of a drug is linked to its ability to bind to specific recognition sites located on intracellular proteins or on proteins that are integrated in the lipid bilayer of cellular membranes. These proteins possess, or are linked to other proteins that possess, the ability to generate an intracellular biochemical signal. The diversity of signaling systems may be better appreciated when considering the following examples: G-protein-coupled receptors, ligand-gated ion channels, voltage-operated cation channels, tyrosine kinase receptors, and transporters. Increasing knowledge of the molecular basis of a given pathology (pathophysiology) unravels the potential implication of one or more proteins in the disease process and it is expected that pharmacological modification of the function of these proteins may afford treatment of the disease. Ligand–receptor or drug–enzyme interaction is expected to alter cellular function but in intact cells, a number of functional events may interfere with the initial intracellular signaling and modify the final response. The aim of in vivo experiments is to confirm that the compound has the therapeutic efficacy expected, that is, that it would interfere with a pathological mechanism involved in an illness and induce beneficial effects.