Assay Method Information

Assay Name:  SSTR4 I-125 Somatostatin Competition Binding Assay
Description:  This membrane-based assay measures the ability of compounds to competitively inhibit binding of I-125 labeled somatostatin to SSTR4 in membranes from CHO-K1 that overexpress SSTR4. Membranes from CHO-K1 cells overexpressing SSTR4 are purchased from Perkin Elmer (catalog number ES-524-M400UA). Test compounds are suspended in DMSO and then diluted in assay buffer (25 mM HEPES pH 7.4, 10 mM MgCl2, 1 mM CaCl2), 0.5% BSA) plus 0.2 nM I-125 labeled somatostatin (Perkin Elmer catalog number NEX389). Fifty μL of compound/I-125 somatostatin in assay buffer are added per well to 96-well poly-propylene plate. Then 1 μg of SSTR4 membranes in 50 μL assay buffer are added per well. The Plate is incubated for 60 minutes at room temperature. FilterMat A filters (Perkin Elmer catalog number 1450-421) are pre-soaked in 0.5% PEI (Sigma catalog number P3143). The contents of the assay plate are transferred to filters with a TomTech harvester and washed 5 times with 20 mM HEPES, 100 mM NaCl. The filters are dried in a microwave oven then transferred to sample bag containing a scintillator sheet (Perkin Elmer catalog number 1450-441). The scintillator sheets are melted to filters using a heat block. The filters are then read in a MicroBeta scintillation counter. Binding Ki curves are generated using Activity Base for Screening Data Management and the results are reported as pIC50.
Affinity data for this assay
 

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