FIGURE 4.  Dose response of agonist-induced sst₃ internalization. HEK-sst₃ cells were treated with 1 nmol/L, 10 nmol/L, 100 nmol/L, 1 µmol/L, or 10 µmol/L of somatostatin-28 or KE108. Also included are cells treated with 100 nmol/L somatostatin-28 plus 5 µmol/L sst₃-ODN-8 or with 1 µmol/L somatostatin-28 plus 50 µmol/L sst₃-ODN-8. After incubation with peptides, cells were processed for immunocytochemistry, and internalized sst₃ was quantified. This experiment shows that somatostatin-28 and KE108 are of similar potency in inducing sst₃ internalization. Somatostatin-28–induced internalization effect is efficiently abolished by excess of sst₃-ODN-8