Background and Objective: Radiotracer diagnosis of insulinoma, can be done using somatostatin
or glucagon-like peptide 1 (GLP-1). Performance of GLP-1 antagonists tends to be better
than of agonists.
Methods: We investigated the uptake of the antagonist exendin (9-39), radiolabeled with technetium-
99m. Two different sites of the biomolecule were selected for chelator attachment.
Results: HYNIC-βAla chelator attached to serine (C- terminus) of exendin, was associated with
higher tumor uptake than to aspartate (N- terminus).
Conclusion: The chelator position in the biomolecule influenced receptor uptake.