Percoll®
Colloidal PVP-coated silica used for density-gradient centrifugation of cells, viruses and subcellular particles.
perpetrator
a drug that alters the clearance of a victim drug
PgP
P-Glycoprotein. A human ABC transporter also known as MDR1 or ABCB1. It is extensively distributed and expressed in normal cells such as those lining the intestine, liver cells, renal proximal tubular cells, and capillary endothelial cells comprising the blood-brain barrier.
pharmacokinetics
Study of the intake of drugs in the body including absorbtion, distribution, transformation and excretion.
Phase I
Biotransformation, involves hydrolysis, reduction, and oxidation. These reactions expose or introduce a functional group. Many times, this is the rate-determining step of biotransformation.
Phase II
Biotransformation, involves glucuronidation, sulfation, acetylation, methylation, conjugation with glutathione and conjugation with amino acids. Promotes the excretion of foreign chemicals.
PM
Poor metabolizer. A term used to distinguish individuals who, for genetic reasons, do not express an enzyme from those who do. The latter individuals are known as EM, for extensive metabolizers.
polyclonal
Arising from more than one cell. Polyclonal antibodies are derived from animal antisera and contain a variety of antibodies that often recognize multiple antigenic determinants on an immunogen.
polymorphism
Genetic variation. An enzyme that is expressed in some individuals but not others is said to be a polymorphic enzyme, as are enzymes that are encoded by the same gene locus but differ by one or more amino acids. These latter enzymes are also known as allelic variants or allelozymes.
PPARa
The receptor (DNA-binding protein or transcription factor) that mediates the induction of CYP4A enzymes by clofibrate and other peroxisome proliferators. PPARa stands for peroxisome proliferator-activated receptor.
proteins
Large molecules formed from amino acids linked by peptide (amide) bonds. Some proteins are glycosylated (linked to carbohydrates) or modified with other substances.
PXR
The receptor (DNA-binding protein or transcription factor) that mediates the induction of CYP3A enzymes by agents such as rifampin (human) and pregnenolone-16a-carbonitrile (rodents). PXR stands for pregnane X receptor.