Effects of estradiol and progesterone on cytochrome P4501A1 expression in Hepa 1c1c7 cells.

The effects of estradiol and progesterone on the expression of cytochrome P4501A1 were investigated in Hepa 1c1c7 cells. Both steroids, at 10 microM concentration, increased P4501A1-mediated 7-ethoxyresorufin O-deethyalase activity and amounts of its immunoreactive protein and CYP1A1 mRNA. Gel shift assay revealed that the steroids could induce both AhR transformation and binding of the ligand-AhR complex to its specific DNA recognition site. Transient transfection demonstrated that 5'flanking region of CYP1A1 could respond to the steroid action. The competitive binding assay showed that the steroids bound to AhR with moderate affinity. These results suggested that steroidal structure can be AhR ligands and induce CYP1A1 expression in AhR-dependent manner.