Figure 8

The effects of E2 on the TCDD-stimulated expression of the cytochrome P4501A (CYP1A) gene. After 48 hrs of culture the fish hepatocytes were left untreated or were treated with a fixed concentration of TCDD or TCDD plus increasing concentration of E2. Following a 12-h treatment period, total cellular RNA was isolated. Total RNA (20 μg per lane) was electrophoresed through a formaldehyde-containing agarose gel, transferred to a nylon membrane and sequentially hybridized to [α-³²P]dCTP labelled cDNAs specific for cytochrome P4501A (CYP1A) and β-actin. The results shown are from a representative experiment repeated three times. The numbers correspond to treatments as follows: #1: Control sample (cells treated with DMSO); #2: Cells treated with 10 nM TCDD; #3, 4, 5 and 6: Cells treated with 10 nM TCDD plus increasing concentrations of E2 (0.1, 1, 10 and 100 nM respectively); #7: Cells treated with 10 nM TCDD+ 1 μM testosterone; #8: Cells treated with 10 nM TCDD + 10 nM E2 + 1 μM tamoxifen; #9: Cells treated with 10 nM TCDD + 100 nM E2 + 1 μM tamoxifen; #10: Cells treated with 10 nM TCDD + 1 μM tamoxifen.