Astatine in Biology and Nuclear Medicine

Abstract

After oral administration to rats, astatine is absorbed rapidly from the gastrointestinal tract and accumulates in the thyorid gland at a rate similar to that observed after intravenous or intraperitoneal injection [1]. A study of ²¹¹At uptake into the thyroid from patients suffering from thyroid diseases was performed by Hamilton et al. [1]. Although the interpretation of the results is difficult (as is frequently the case with human studies) it seems likely that astatine uptake from the human gastrointestinal tract is also rapid. The uptake of the astatine analog ¹³¹I from the gastrointestinal tract of man is, of course, much better known from many investigations in nuclear medicine. It can be assumed that more than 90% of ¹³¹I is absorbed within two hours after oral administration. A very similar behavior is shown by pertechnetate (references in [2]). As already demonstrated for other nuclides, the absorption of ²¹¹At will probably be influenced by the status of the individual (fasted or nonfasted) as well as by the chemical form in which it is incorporated. The first biological study performed with astatine (at that time called ekaiodine) had already shown that this element is also absorbed rapidly from a subcutaneous deposition site [3]. Its transcutaneous absorption has not been investigated experimentally. However, it can be assumed by analogy with iodine, that some resorption through the intact skin can occur. When inhaled, iodine is rapidly absorbed through the lung, most probably the same holds for ²¹¹At, but experimental data are lacking.