Glucagon-like peptide-1 receptor (GLP-1R) is a molecular target for imaging of pancreatic beta cells. We compared the ability of [Nle14,Lys40(Ahx-NODAGA-64Cu)NH2]-exendin-4 ([64Cu]NODAGA-exendin-4) and [Nle14,Lys40(Ahx-NODAGA-68Ga)NH2]-exendin-4 ([68Ga]NODAGA-exendin-4) to detect native pancreatic islets in rodents.Procedures
The stability, lipophilicity and affinity of the radiotracers to the GLP-1R were determined in vitro. The biodistribution of the tracers was assessed using autoradiography, ex vivo biodistribution and PET imaging. Estimates for human radiation dosimetry were calculated.Results
We found GLP-1R-specific labelling of pancreatic islets. However, the pancreas could not be visualised in PET images. The highest uptake of the tracers was observed in the kidneys. Effective dose estimates for [64Cu]NODAGA-exendin-4 and [68Ga]NODAGA-exendin-4 were 0.144 and 0.012 mSv/MBq, respectively.Conclusion
[64Cu]NODAGA-exendin-4 might be more effective for labelling islets than [68Ga]NODAGA-exendin-4. This is probably due to the lower specific radioactivity of [68Ga]NODAGA-exendin-4 compared to [64Cu]NODAGA-exendin-4. The radiation dose in the kidneys may limit the use of [64Cu]NODAGA-exendin-4 as a clinical tracer.