Fig. 2.

Immunofluorescence microscopy-based internalisation assay on HEK-sst2 cells. Immunofluorescence microscopy-based internalisation assay with HEK-sst2 cells showing the sst2 internalisation induced by [Tyr³]octreotide (TOC) is efficiently antagonised by SS-03 and SS-04. Control experiment showing membrane bound sst2-receptor in the absence of peptide. The agonist, TOC, triggered massive sst2-receptor internalisation at a concentration of 10 nM. The antagonists SS-03 and SS-04 failed to induce sst2 internalisation even at a concentration of 1 μM. Further, both SS-03 and SS-04 at a concentration of 1 μM efficiently blocked the agonist (TOC, 10 nM)-mediated sst2-receptor internalisation