Table 3.
Site-specific stimulation of sst2A receptor phosphorylation by somatostatin analogs
| Analog | Receptor phosphorylation |
|||
|---|---|---|---|---|
| Ser341/343 |
Thr353/354 |
|||
| EC50 (nm) | Max response (% of SS14) | EC50 (nm) | Max response (% of SS14) | |
| SS14 | 2.5 ± 0.6 | 100 | 1.1 ± 0.1 | 100 |
| KE108 | 2.5 ± 0.5 | 65.2 ± 3.1 | 17.3 ± 1.5 | 66.5 ± 11.6 |
| SOM230 | >200 | 48.4 ± 9.7 | 49.5 ± 1.1 | 74.8 ± 2.8 |
The dose response for agonist stimulation of sst2A receptor phosphorylation was measured at Ser341/343 and Thr353/354 as described in Fig 3. The values for EC50 and maximal (Max) effect were calculated by nonlinear regression analysis of sigmoidal dose-response curves as described under Materials and Methods and are given as the mean ± sem of the values obtained in at least three independent experiments. The effect of each analog on receptor phosphorylation at distinct sites was analyzed using ANOVA and Dunnett's multiple comparison test. The EC50 values for Ser341/343 phosphorylation differed significantly from the EC50 values for Thr353/354 phosphorylation for both SOM230 (P < 0.05) and KE108 (P < 0.01) but not for SS14.