Evaluation of induction of CYP3A mRNA using the HepG2 cell line and reverse transcription PCR

Cytochrome P-450 3A (CYP3A) is a drug-metabolizing enzyme dominant in the h uman liver. We have designed a useful method for evaluation of induction of CYP3A mRNA by various drugs using HepG2 cells known to retain liver-cellul ar functions. Using semi-quantitative reverse transcription-PCR (RT-PCR), w e demonstrated that cultured HepG2 cells constitutively expressed CYP3A mRN A. This mRNA was expressed at high levels in culture for several days and w as further induced by several drugs (e.g. rifampicin (RFP), dexamethasone). Treatment of HepG2 cells with RFP induced CYP3A mRNA in a dose- and time-d ependent manner. Cells in culture for 48 h with 1 and 50 mu mol/l RFP incre ased 2.7- and 5.0-fold in CYP3A mRNA expression in comparison with untreate d controls, respectively. In contrast, no change in the amount of CYP3A mRN A was observed when the cells were treated with cimetidine a which has been shown to inhibit CYP3A activity. Our method using a combination of HepG2 c ells and RT-PCR allowed evaluation of the degree of induction of CYP3A mRNA both easily and rapidly.