INHIBITION BY PROPYLTHIOURACIL OF THE EXTRATHYROIDAL FORMATION OF TRIIODOTHYRONINE FROM THYROXINE

Abstract

ABSTRACT Thyroidectomized rats were injected daily with 1.9 μg/100 g body weight of 125I-labelled L-thyroxine (T*4). When isotopic equilibrium was attained, half the experimental group was injected twice with 2 mg of propylthiouracil at a 24 h interval. Animals were killed 7 h after the last dose and the amounts of T*4 and labelled iodide and T3 in peripheral tissues were determined after extraction and paper chromatography. The amount of T3 derived from T4 is significantly lower in tissues of rats receiving PTU.