CHEMBL5737462

Radioligand Binding Assay: Competitive radioligand binding experiments were performed using MEMBRANE TARGET Systems (Perkin-Elmer, Boston, Mass.) for human somatostatin receptors: SSTR1 (ES-520-M400UA), SSTR2A (ES-521-M400UA), SSTR3 (ES523-M400UA), SSTR4 (ES-524-M400UA) and SSTR5 (ES-522-M400UA) receptors. (See Table 1). Respective membrane receptor preparations were prepared in assay buffer (25 mM HEPES, 10 mM MgCl2, 1 mM CaCl2, 0.5% BSA, pH=7.4) at a 1:150 dilution. Binding assays were performed using 1251-Tyr-SRIF 14 (Perkin-Elmer, NEX 3890) dissolved in 1 mM HCl. Binding assays were performed in triplicate for each concentration of ligand in a total volume of 200 μL radioligand (25 μL ligand, 25 μL radioligand, 150 μL receptors) and incubated at room temperature for 90 minutes using a shaking table. Binding was terminated by filtration through GF/B glass fiber filters that were presoaked in 0.5% polyethyleneimine for a minimum of 4 hours. Filters were washed 9× with 1000 μL ice cold wash buffer (50 mM Tris-HCl, pH=7.4, 0.2% BSA). Filters were scored, transferred into plastic test tubes and counted in a gamma counter (Wizard2, Perkin-Elmer). Determination of the Ki for each compound was performed using non-linear regression with GraphPad PRISM-5 software (GraphPad Software, Inc., La Jolla, Calif.).