( Key words: ...)The development of a somatostatin sst4 receptor-binding assay using the LEADseeker Multimodality Imaging System

Key words: somatostatin • receptor binding assay • LEADseeker • SPA Imaging Beads

Somatostatin (SS) is a neurotransmitter/hormone with a wide range of biological actions (1–3) and a reduction in cortical SS levels has been reported in Alzheimer’s and Parkinson’s diseases. The SS analog, octreotide (SMS 201–995), is used clinically in the treatment of certain tumors, carcinoid syndrome, and glucagonoma. Somatostatin inhibits cell proliferation and growth hormone secretion through interaction with SS receptors (4). Five SS receptors have been cloned and many studies have investigated the tissue distribution, expression, binding affinity to SS, and down-stream signal transduction pathways of these five receptors (5, 6). It has also been shown that SS receptors are G protein coupled. All five SS receptors have similar binding affinities to their natural ligand SS; however, they bind SS analogs, such as octreotide, at different affinities.

This application note describes a 384-well somatostatin sst4 receptor-binding assay which has been developed on the LEADseeker™ Multimodality Imaging System.

Materials
Reagents and instrumentation
LEADseeker Multimodality Imaging System 18-1140-71

Polyethyleneimine (PEI) PS SPA Imaging Beads RPNQ0098

(3-[¹²⁵I] iodotyrosyl¹¹) Somatostatin-14(tyr¹¹), IM161-50UCI
1.85 MBq, 50 µCi

Other material required
Human recombinant somatostatin sst4 receptor membrane preparation (Euroscreen, ES-524-M)

Somatostatin-28 (Sigma, S-6135)

Octreotide (Sigma, O-1014)

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