Influence of sodium perchlorate on thiourylene antithyroid drug accumulation in mice

Radiolabelled [35S]propylthiouracil and [35S]methimazole were shown to accumulate in mouse thyroid gland in vivo, with maximal tissue/plasma ratios and maximal intrathyroidal levels of 35S-labelled drug being seen at the lowest dose of drug studied (0.1 micrograms/animal). Pretreatment with sodium perchlorate (10 mg) abolished iodide trapping by the thyroid and caused a fall in accumulation of both [35S]methimazole and [35S]propylthiouracil, although this effect was not seen at higher doses of drug, when tissue/plasma ratios approached unity. These data suggest that thiourylene antithyroid drug accumulation by the thyroid gland does not depend directly on the anion trap, and it is suggested that this accumulation might depend on subsequent intrathyroidal drug metabolism.