6-[124I]Iodo-9-pentylpurine for imaging the activity of the sodium iodide symporter in the brain

Iodide homeostasis and thyroid hormone metabolism in the brain are potentially related to changes in activity of the sodium iodide symporter (NIS). No radiotracers are currently available for imaging brain NIS activity. Here, we synthesized 6-[124I]iodo-9-pentylpurine that can noninvasively measure iodide efflux from the brain and showed that the efflux rate of [124I]I− in NIS knockout mice was 84% lower than that of wild-type mice. Thus, 6-[124I]iodo-9-pentylpurine would be useful for imaging brain NIS activity.