Figure 1.

Binding and signaling of TAL to TRH-R1 and TRH-R2. Competition binding for [³H]MeTRH stimulation of inositol-1,4,5-trisphosphate production (by measuring its degradation product inositolmonophosphate) and stimulation of intracellular calcium release by various doses of TAL in HEK293 cells stably expressing TRH-R1 or TRH-R2 were measured as described in Materials and Methods. The maximal levels of IP1 in a typical experiment were: 2735±47 nmol for TRH at TRH-R1; 3590±91 nmol for TAL at TRH-R1; 3923±77 nmol for TRH at TRH-R2; and 3841±78 nmol for TAL at TRH-R2. The data represent the mean of 2–4 replicates in three experiments.