TABLE 2

Efficacy for stimulation of [³H]IP, internalization, and down-regulation of wild-type and mutant GRP receptors

Stimulation of increases in [³H]IP was determined as described in Fig. 2. The efficacy of [³H]IP stimulation is expressed as the fold increase over basal in total cellular [³H]IP determined as described in Fig. 2 legend. Internalization was assessed as described in Fig. 4 and is expressed as the percentage of total saturable bound ¹²⁵I-[Tyr⁴]Bn that was not removed by acid-stripping. t₈₀ is the time in minutes that was needed for internalizing 80% of maximal calculated as described under Materials and Methods. Down-regulation is expressed as the percentage of decrease in the receptor number (B_max) of cells pretreated with 10 nM Bn compared with control cells processed in parallel. Wild-type GRP-R were down-regulated 61 ± 3% compared with cells not treated with 10 nM Bn. Data are expressed as the mean ± S.E.M. of at least three separate experiments and for each experiment each point was determined in duplicate.