Table 1

Effect of metyrapone, dexamethasone, and TCDD on the expression of reporter genes driven by a minimal inverted XRE motif and by the human CYP1A1 promoter when transiently transfected into HepG2 cells

TreatmentFold CAT Activity versus Control
pTX1X1/invpBLh1A1CAT
Control1 (arb)1 (arb)
MET1.2  ± 0.21.2  ± 0.13
DEX1.0  ± 0.11.0  ± 0.13
MET + DEX1.5  ± 0.2* 2.1  ± 0.331-a
TCDD8.6  ± 0.5* 4.9  ± 0.471-a
TCDD + DEX8.0  ± 0.5* 7.5  ± 1.01-a

HepG2 cells were transfected with either pTXIX/inv or pBLh1A1CAT and treated with inducers as outlined in Materials and Methods. Control, vehicle solvent (0.1% v/v ethanol); MET, 500 μM metyrapone; DEX, 100 nM dexamethasone; MET + DEX, 500 μM metyrapone and 100 nM dexamethasone; 1 nM TCDD; TCDD + DEX, 1 nM TCDD and 100 nM dexamethasone. Data are expressed as the mean ± S.D. of fold activity versus control of three determinations from the same experiment, typical of two separate experiments.

  • 1-a Statistically different-fold induction versus control using Student's t test (two-tailed), P > 95%.