Effect of Dinitrophenol Administration on the Transport and Metabolism of the Thyroid Hormones in Rats

Abstract

Dinitrophenol administration to intact and thyroidectomized (L-thyroxine maintained) rats produced a 50 % decrease in the serum protein-bound iodine and a significant decrease in the amount of 131I-labeled thyroxine bound to the thyroxine-binding protein as determined by starch gel electrophoresis. The addition of dinitrophenol to rat sera produced a similar effect on thyroxine binding. Following the ip injection of 1 μc of 131Ilabeled thyroxine, the total retained radioactivity in thyroidectomized stabilized rats was measured 3 times daily for 14 consecutive days. This was done by using a large well liquid scintillation counter (Armac). The disappearance of radioactivity from the whole animal may be represented as 2 major components, an initial fast component with a biological half-life of 24 hr and a second and slower component with a half-life of 113 hr. The slower component became apparent on the fifth day, by which time 85 % of the administered radioactivity had been excreted. Dinitrophenol administr...