Acute effects of various doses of iodide on thyroid iodine autoregulation

Abstract

Analytical ion microscopy (AIM) was used to determine alterations in the thyroid follicular lumen¹²⁷I stores of Wistar rats injected with different doses of¹²⁹I (low specific activity radionuclide). Animals fed a normal iodine diet (10 μg¹²⁷I/d) were divided into four groups: control group and three treated groups injected ip 24 h before sacrifice with¹²⁹I at doses of 10 μg (group 1), 30 μg (group 2), and 8500 μg (group 3). AIM was performed on thyroid semithin sections. The mean¹²⁹I concentration increased with the dose injected from group 1 (0.44±0.03 μg/mg, mean ± SEM) to group 2 (2.05±0.14 μg/mg) and decreased in group 3 (0.57±0.08 μg/mg). When compared to control group (4.14±0.17 μg/mg), the mean¹²⁷I concentration was not changed in group 1 (4.52±0.07 μg/mg), but altered in the other groups: It was significantly increased (7.14±0.41 μg/mg) in group 2 and slightly decreased (3.11±0.26 μg/mg) in group 3. These results underline the interest of AIM in the study of the effects of various doses of iodide on the thyroid autoregulation by iodide, a trace element actively trapped by this gland.