Figure 1.

Recycling of the internalized ¹²⁵I-hCG in cells transfected with the myc-hLHR-wt or myc-hLHR-L457R. 293T cells were transiently transfected with the hLHR-wt (▲) or -L457R (■) and incubated with ¹²⁵I-hCG (1 nM, Kd = 1-3 nM) for 20 min at 37°C. At this time the free and bound hormone were removed and the cells were further incubated at 37°C for 2 h in medium containing an excess of non-radioactive hCG. The amount of recycled ¹²⁵I-hCG (surface bound + intact hormone released, see Table 1) was then measured at the times indicated as described in Materials and Methods. Results are expressed as a percent of the total intracellular ¹²⁵I-hCG radioactivity present at the end of the binding and internalization period (defined as t = 0 in the figure) and they represent the mean ± range of two independent transfections. At t = 20 min the amount of internalized radioactivity varied between 30,000 and 60,000 cpm/well.