Synthesis and biological evaluation of 17-[131I]iodo-9-telluraheptadecanoic acid, a potential imaging agent.

A method has been developed for the preparation of terminal halogenated tellurium fatty acids (X-R-Te-R'-COOH). The synthesis and physical properties of 17-bromo- and 17-iodo-9-telluraheptadecanoic acid (17-iodo-9-THDA) are described. The radiohalogenated agents are of interest as a result of their expected pronounced and prolonged heart uptake and potential use for evaluation of regional myocardial fatty acid metabolism. Evaluation in rats indicates that the myocardial uptake of 17-[131I]iodo-9-telluraheptadecanoic acid (17-[131I]iodo-9-THDA) is accompanied by significant in vivo deiodination. A comparison of the heart uptake and deiodination of 17-[131I]iodo-9-THDA and 16-[131I]iodopalmitic acid has demonstrated a close similarity in blood levels of radioactivity and thyroid uptake of radioiodide after administration of these agents to rats. These data suggest that the mechanism of deiodination of terminal radioiodinated alkanoic acids primarily results from direct cleavage of the carbon-iodine bond and not from loss of radioiodine from the final catabolite.