ABSTRACT
Cytochrome P450 (CYP) enzymes form a gene superfamily that are involved in the metabolism of a variety of chemically diverse substances ranging from endogenous compounds to xenobiotics, including drugs, carcinogens, and environmental pollutants. Induction of CYP expression by xenobiotics has been reported in mainly ways: induction potential, EC50, and “potency index”. Subsequent studies with DFP indicated that the human oxidative pathways were catalyzed by CYP3A and CYP1A, as demonstrated by turnover with recombinant CYP enzymes. The classical CYP3A probe is testosterone, which is known to undergo CYP3A4-dependent 6ß-hydroxylation. Ferrini et al. have described culture conditions to maintain human hepatocytes for several weeks while retaining CYP inducibility. CYP3A4 activity was assessed with DFB prior to RNA isolation. CYP3A4, CYP3A5, and CYP3A7 mRNA analysis using real-time TaqMan polymerase chain reaction was conducted. The more conventional analytical methodology exemplified by Western blot and substrate probes lack the sensitivity and selectivity to profile all CYPs.
