FIG. 1.

Ligand binding confers thermal stability to Sprague–Dawley rat hepatic cytosolic AhR. Unoccupied receptor: Rat hepatic cytosol (2 mg/ml) was incubated at the indicated temperature and aliquots (500 μl) were removed at the indicated times incubated with 2nM [³H]TCDD in the absence or presence of 200nM TCDF for 2 h. Occupied receptor: Rat hepatic cytosol (2 mg/ml) was incubated with 2nM [³H]TCDD in the absence or presence of 200nM TCDF for 2 h, stripped with DCC to remove free and loosely bound ligand, and then incubated with cold TCDF (to 200nM) for the indicated times at the indicated temperatures. For both unoccupied and occupied receptor incubations, specific binding of [³H]TCDD was determined using the HAP assay and data are presented as the mean ± SD of triplicate incubations.