Diagnostic agents for the brain and myocardium using radioactive iodine for labelling nuclide

Development of radioactive diagnostic agents focusing on the introduction of radioactive iodine for labelling nuclide is reported. 123I-3-iodo-α-methyl-L-tyrosine (123I-L-AMT) was selected. The accumulation, clearance, and inhibition of 125I-L-AMT was evaluated using mice, and compared with those of 14C-L-Tyr. Higher accumulation and clearance of 125I-L-AMT was observed in the brain of mice. In rat brain slices, the effects of inhibition on 125I-L-AMT accumulation was almost comparable to that of 14C-L-Tyr. In the experiment using dogs, brain orbitomeatal axial tomography was performed using SPECT, revealing high accumulation. As for myocardium, 123I-3-iodo-p-hydroxy-l-norephedrine (123I-PHNE) which has similar chemical structure to AMT was used. In the experiment of mice, 125-PHNE showed high accumulation, however, clearance time was short. High accumulation was also observed in mice. Therefore, further study of development of metabolic function diagnostic agent using radioactive iodine as a labelling nuclide is anticipated. (S.Y.)