Figure 4

TCDD- mediated down-regulation of vitellogenin and estrogen receptor α mRNAs. Slot blot hybridization analysis of hepatic VTG (A) and estrogen receptor alpha (B) after treatment with 17 β-estradiol (E2) and increasing concentrations of TCDD. After 48 hrs of culture, the cells were co-treated with a constant concentration of E2 (10 nM) and increasing concentrations of TCDD for 12 hrs. Total RNA (7.5 μg) was applied per slot and sequentially hybridized with [α-³²P]dCTP labelled cDNA probes specific for VTG and ERα. Radioactivity in each slot was quantified using phosphoimager as photo stimulated luminiscence (PSL). The cells were treated as follows: Control: Cells treated with dimethylsulfoxid (DMSO) only. E2: Cells treated with 10 nM E2 for 12 hrs. Lane 3 – 7 labelled 0.1, 0.5, 1, 5, and 10: Cells co-treated with 10 nM E2 and increasing concentrations of TCDD (0.1, 0.5, 1, 5, and 10 nM, respectively) for 12 hrs. The PSL values of three independent experiments and their means are shown in the plot diagram. Asterisk indicates significant difference (P < 0.05) with respect to the E2-treated sample (Dunnett's test).