STUDIES ON THE FIXATION OF RADIOACTIVE IODINE BY THE RABBIT THYROID1

THE GREAT RAPIDITY with which the thyroid concentrates iodine following the administration of soluble iodides would seem to involve a consideration of chemical transformations occurring within this gland. Recent data (Perlman, et al., 1941; Morton, et al., 1941; Mann, et al., 1942; Morton, et al., 1942), obtained with radioactive iodine, have shown that circulating iodide is rapidly incorporated into the diiodotyrosine and thyroxin fractions of thyroid protein. In the shortest interval employed, Mann, Leblond, and Warren (1942) found considerable quantities of labeled iodine in the organic fractions (particularly the diiodotyrosine fraction) as early as 30 minutes following the administration of tracer doses of radioactive iodide. In studying the rate of fixation of administered (exogenous) iodide a number of investigators (Marine and Feiss, 1915; Hertz, et al., 1940; Hamilton and Soley, 1940; Lein, 1941; Leblond and Sue, 1941) have determined that the rate of concentration of iodine by the thyroid is greatest during the first 10 minutes following administration.