Studies on the Thyroidal Uptake of Astatine in the Rat*†

THE comparative approach to the study of thyroid function, as illustrated by the studies of Gorbman (1), Gudernatsch (2) and Payne (3) on lower vertebrates, has been profitable. Another type of comparative approach has been made, chiefly by Baumann (4), by studying the ability of the thyroid to accumulate various members of the halogen group of elements. This work dates from the fundamental demonstration by Baumann that the thyroid is capable of concentrating iodine. The introduction of radioisotopes of iodine in the investigation of thyroid function by Hertz, Roberts and Evans (5) and Hamilton, Soley and Eichorn (6) has helped to advance these studies. Likewise, the utilization of radioisotopes of fluorine and bromine (Perlman (7), Wallace (8)) advanced the study of thyroid function concerning these halogens (Table 1). Following the discovery of Element 85 (astatine) by Corson, MacKenzie and Segre in 1940 (9), it is not surprising that the ability of the thyroid to accumulate this newest and heaviest radiohalogen would be tested. Indeed, Hamilton (10, 11, 12), utilizing astatine211, a 7.5-hour alpha particle and x-ray emitter, demonstrated the accumulation of astatine in the thyroid gland of the guinea pig, rat, monkey and man. Hamilton further showed that the thyroid apparently accumulates astatine in a manner similar to the accumulation of I131, although at a reduced rate, and that excessive amounts of iodide would depress the accumulation of astatine, whereas exogeneous TSH would increase the accumulation of astatine. Hamilton also presented data from extensive studies on the tissue distribution of astatine and the radiation effects resulting from its alpha particles. In addition, Pickering and Fisher (13) attempted radiothyroidectomy with astatine in rhesus monkeys without success.