FIGURE 1.

Dissociation of prebound ¹²⁵I-TSH from cells stably expressing the TSH holoreceptor (A) and TSHR ECD-GPI (B). Confluent holoreceptor- and TSHR ECD-GPI-expressing cells in 24-well plates were preincubated for 4 h at room temperature in binding buffer containing ¹²⁵I-TSH. After rinsing to remove unbound ¹²⁵I-TSH, the cells were incubated at room temperature for the indicated times in binding buffer lacking ¹²⁵I-TSH (see “Experimental Procedures”). Where indicated (+ TSH), the buffer was supplemented with 100 milliunits/ml bovine TSH. After buffer removal, the cells were solubilized, and residual radioactivity was measured. Each point represents the mean ± range of values from duplicate wells of cells. Similar data were obtained in replicate experiments with the TSH holoreceptor (n = 7) and TSHR ECD-GPI (n = 2).