Tellurium-123m-labeled 23-(isopropyl telluro)-24-nor-5α-cholan-3β-ol: a new potential adrenal imaging agent

Tellurium-123m-labeled 23-(isopropyl telluro)-24-nor-5α-cholan-3β-ol (24-telluracholestanol, or 23-ITC) has been prepared as a potential adrenal-imaging agent. The new agent was synthesized by the coupling of 3β-acetoxy-23-bromo-24-nor-5α-cholan with Te-123m-labeled sodium isopropyl tellurol. Tissue distribution experiments in both male and female rats indicate a high adrenal concentration of radioactivity following administration of this agent. In female rats the adrenal glands accumulated 4.5% of the injected radioactivity only 1 day after administration of Te-123m-23-ITC. The adrenal-to-liver ratio was 42 after 1 day, and this increased to 100 after 3 days. Chromatographic analyses of lipid extracts from adrenal, ovary, liver, and lungs suggest that this agent is metabolized by these tissues. Examination of the rats' excretory products has indicated that approximately 50% of the administered radioactivity is excreted in the feces with 5 days after injection of Te-123m-23-ITC. Moreover, the adrenals and ovaries of rats have been clearly imaged with this agent, both with a rectilinear scanner and with an RC type of proportional-counter camera