FIGURE 5.  sst₅ internalization is induced by native somatostatin-28 but not by high-affinity synthetic sst₅ agonists. HEK-sst₅ cells were treated either with vehicle (no peptide); with 1 nmol/L, 10 nmol/L, 100 nmol/L, or 1 µmol/L somatostatin-28; or with 1 µmol/L KE108, 1 µmol/L BIM-23244, or 1 µmol/L L-817,818. After incubation with peptides, cells were processed for immunocytochemistry. Dose-response experiment with somatostatin-28 shows that it can elicit sst₅ internalization. This is, however, not true for sst₅ agonists KE108, BIM-23244, and L-817,818. Note also presence of intracellular sst₅ even when cells were treated with vehicle alone (no peptide). All images are composed of 2 single pictures.