Synthesis and evaluation of radioiodinated substituted β-naphthylalanine as a potential probe for pancreatic β-cells imaging

A non-invasive imaging technique capable of relating a signal from the β-cells to their mass will be of immense value in understanding the progression of diabetes. Several molecular markers have indeed been identified and investigations are ongoing aimed at accomplishing the said goal. These include pancreatic islet antigen (IC-2), somatostatin receptors (SSTRs), and sulfonylurea receptors (SURs) on the pancreatic β-cells. Therefore investigations exploiting the potential application of the radiolabeled ligands for these receptors for β-cell imaging are receiving intensive research attention. Radioiodinated peptidomimetic based on β-naphthylalanine and n-hexanediamine has been synthesized. The molecule was subjected to in vitro and in vivo evaluation. Radioligand binding studies on CHO cell line expressing the SSTR2 showed very low affinity. Nonetheless, biodistribution in normal mice showed significant uptake in the pancreas. There was partial blockage of the pancreatic uptake when excess of the peptidomimetic was coinjected. The result implies that the pancreatic uptake was receptor mediated but may not involve the SSTR2 and therefore warrants further investigation.