Effect of chronic graded doses of iodide on thyroid hormone synthesis.

Abstract

Experiments were performed to determine the effects of graded chronic doses of iodide on thyroid hormone synthesis. Rats were given a low iodine diet for a week and were then given a diet supplemented with graded doses of iodide (5-3645 μg of iodide in 20 g of diet) for 10 days until the time of sacrifice. Rats were also given a single intravenous injection of 131I 1 hr before sacrifice. 127I content of thyroid and plasma was determined by the method of Baker. Thyroidal total 127I uptake per unit of time was measured as thyroidal total 131I divided by the mean of the concentrations of inorganic 131I in plasma collected 2 min and 1 hr after the injection of 131I and multiplied by the concentration of inorganic m I in plasma collected 1 hr after 131I. Thyroidal organic 131I formed per unit of time was calculated from thyroidal organic 131I instead of thyroidal total 131I. These calculations could be expressed as thyroidal 131I clearance multiplied by plasma inorganic 127I or thyroidal 131I multiplied by the...