A new technique for in vivo imaging of specific GLP-1 binding sites: first results in small rodents

M. Gotthardt, G. Lalyko, J. van Eerd-Vismale, B. Keil, T. Schurrat, M. Hower, P. Laverman, T. Behr, O. Boerman, B. Göke and M. Béhé

Department of Nuclear Medicine, Radboud University Nijmegen Medical Center, Postbus 9101, 6500 HB Nijmegen, The Netherlands. m.gotthardt@nucmed.umcn.nl
Dec, 2006



In vivo imaging of GLP-1 receptor-positive tissues may allow examination of physiologic and pathophysiologic processes. Based on the GLP-1 analog Exendin 4, we have developed a radiolabeled compound specifically targeting the GLP-1 receptor (DTPA-Lys40-Exendin 4). This work aims to detect GLP-1 receptor-positive tissues by biodistribution studies and in vivo small animal imaging studies. For in vivo imaging, a high-resolution multi-pinhole SPECT (single photon emission computed tomography) system was used in conjunction with an MRI (magnetic resonance imaging) system for image fusion.DTPA-Lys40-Exendin 4 can be labeled with 111In to high specific activity (40 GBq/micromol). The radiochemical purity reliably exceeded 95\%. Using this compound for in vivo small animal imaging of rats and mice as well as for biodistribution studies, specific GLP-1 binding sites could be detected in stomach, pancreas, lung, adrenals, and pituitary. Receptor-positive tissues were visualized with a high-resolution SPECT system with a resolution of less than 1 mm.The new technique using DTPA-Lys40-Exendin 4 allows highly sensitive imaging of GLP-1 receptor-positive tissues in vivo. Therefore, intra-individual follow-up studies of GLP-1 receptor-positive tissue could be conducted in vivo.