TheIn VitroStimulation of Thyroidal Activity by Propylthiouracil1

Abstract

In vitro studies indicated that a small amount of propylthiouracil (10^-8M) added to the medium significantly increased the total uptake of radioiodine by rat thyroid slices under both aerobic and anaerobic conditions, and significantly increased radioiodine uptake by sheep thyroid slices under aerobic conditions. Chromatography of the propylthiouracil treated slices indicated a significant increase in total radioactivity, a decrease in the ratio of radioiodide to organic radioiodine compounds (I-/I_o), and a decrease in the ratio of radiomonoiodotyrosine to radiodiiodotyrosine (MIT/DIT). There was, in addition, a significant increase in oxygen consumption by rat thyroid slices when treated with small amounts of propylthiouracil. The in vitro results indicate a direct stimulatory effect by small amounts of propylthiouracil on both rat and sheep thyroid slices resulting in an increase in oxygen consumption, radioiodine uptake, and radiodiiodotyrosine formation.