Effect of Propylthiouracil and Thyroid-Stimulating Hormone on Glucose Oxidation in Rat Thyroid Tissue

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Abstract
Previous observations that small amounts of propylthiouracil increased the uptake of radioiodine and the consumption of oxygen by rat thyroid slices led to study of the effect of propylthiouracil on the metabolism of C14 labeled glucose. A high concentration of propylthiouracil (10−3M) in the medium diminished the production of C14O2 by rat thyroid slices, at 1 hour, from both glucose-1-C14 and glucose-6-C14. However, with small doses of propylthiouracil (10−8M), the production of C14O2 from glucose- 6-C14 was markedly stimulated (10-fold; P14O2 from glucose-1-C14 was still inhibited (P14 to C14O2 but had no significant effect on the production of C14O2 derived from glucose-6-C14. The results suggest that small amounts of propylthiouracil stimulate the production of C14O2 from glucose-6- C14 by modifying the various pathways of carbohydrate metabolism in rat thyroid slices (possibly by a stimulation of the Embden- Meyerhof pathway) and that this stimulation is qualitatively different from that of thyrotropin.