Definitions of Commonly Used
Pharmacological Terms
Absorbance
Absorbance is used for assays such as ELISA
assays, protein and nucleic acid quantification or enzyme activity assays (i.e.
in the MTT assay for cell viability). A light source illuminates the sample
using a specific wavelength (selected by an optical filter, or a
monochromator), and a light detector located on the other side of the well
measures how much of the initial (100 %) light is transmitted through the
sample: the amount of transmitted light will typically be related to the
concentration of the molecule of interest.
ADME
An acronym in pharmacokinetics and
pharmacology for absorption, distribution, metabolism, and excretion, and
describes the disposition of a pharmaceutical compound within an organism.
Agonist
A drug that binds to and activates a
receptor. Can be full, partial or inverse. A full agonist has high efficacy,
producing a full response while occupying a relatively low proportion of
receptors. A partial agonist has lower efficacy than a full agonist. It
produces sub-maximal activation even when occupying the total receptor
population, therefore cannot produce the maximal response, irrespective of the
concentration applied. An inverse agonist produces an effect opposite to that
of an agonist, yet binds to the same receptor binding-site as an agonist.
Allosteric Modulator
A drug that binds to a receptor at a site
distinct from the active site. Induces a conformational change in the receptor,
which alters the affinity of the receptor for the endogenous ligand. Positive
allosteric modulators increase the affinity, whilst negative allosteric
modulators decrease the affinity.
Antagonist
A drug that attenuates the effect of an
agonist. Can be competitive or non-competitive, each of which can be reversible
or irreversible. A competitive antagonist binds to the same site as the agonist
but does not activate it, thus blocks the agonist's action. A non-competitive
antagonist binds to an allosteric (non-agonist) site on the receptor to prevent
activation of the receptor. A reversible antagonist binds non-covalently to the
receptor, therefore can be "washed out". An irreversible antagonist
binds covalently to the receptor and cannot be displaced by either competing
ligands or washing.
AUC
The area under the plasma (serum, or blood)
concentration versus time curve.It is used in toxicology, biopharmaceutics and
pharmacokinetics.
BALB/c
An albino strain of laboratory mouse from
which a number of common substrains are derived. BALB/c substrains are
"particularly well known for the production of plasmacytomas on injection
with mineral oil," an important process for the production of monoclonal
antibodies. They are also reported as having a "low mammary tumour
incidence, but do develop other types of cancers in later life, most commonly
reticular neoplasms, lung tumours, and renal tumours.
Bmax
The maximum amount of drug or radioligand,
usually expressed as picomoles (pM) per mg protein, which can bind specifically
to the receptors in a membrane preparation. Can be used to measure the density
of the receptor site in a particular preparation.
C57BL/6
C57BL/6 often referred to as "C57
black 6" or just "black 6" is a common inbred strain of lab
mouse. Dark brown, nearly black, coat. Easily irritable temperament. They have
a tendency to bite. The immune response of mice from the C57BL/6 strain
distinguish it from other inbred strains like BALB/c.
CYP
The cytochrome P450 superfamily. The
function of most CYP enzymes is to catalyze the oxidation of organic
substances. The most common reaction catalyzed by cytochromes P450 is a
monooxygenase reaction. RH (organic substrate) + O2 + 2H+ + 2e– → ROH + H2O.
CYP families in humans divided among 18 families of cytochrome P450 genes and
43 subfamilies.
Cheng-Prusoff Equation
Used to determine the Ki value from an IC50
value measured in a competition radioligand binding assay:
Cheng-prusoff EquationWhere [L] is the
concentration of free radioligand, and Kd is the dissociation constant of the
radioligand for the receptor.