THE THYROIDAL UPTAKE, RETENTION AND IODINE POOL IN RATS UNDER CONTROLLED IODIDE DIET¹

Abstract

THIS laboratory has recently shown (Burns et al. 1951) by the in vivo method, that the biologic half-life of radioiodine in the normal human is approximately 100 days. The subjects for investigation were in the steady state and received a more than adequate iodide diet (Boston area). The divergent values given in the literature for the fractional uptake, biologic half-life, iodine pool of the thyroid and the quantity of thyroxin secreted per day suggested that a study of these factors in rats under strict dietary control might show to what extent they are dependent on the level of dietary iodide. Three levels of the steady state and two series approaching the above condition were chosen for investigation. It was desirable to use a method which, while avoiding anesthesia and sacrifice of the animal, would allow frequent, precise and convenient measurements of I131 in the living thryoid. Our method is a modification of that used by Raben.