Effects of Inorganic Iodide on Thyroid Stimulationin Vitro

Abstract

Since inorganic iodide has been shown to stimulate intermediary carbohydrate metabolism in thyroid slices, studies were done to determine whether the effects of TSH [thyrotropin] and/or LATS [long-acting thyroid stimulator] on thyroidal glucose oxidation and phospholipogenesis were modified by the presence of iodide in the medium. NaI in concentrations (1.7 x 10-3 M, 3.3 x 10-4 M) which either stimulated or were without effect on oxidation of glucose -1-14C or 32P incorporation into phospho-lipids by sheep thyroid slices consistently inhibited TSH-induced stimulation of thyroidal glucose oxidation and phospholipogenesis. The same concentrations of NaI did not affect, and in a few instances augmented, LATS-induced stimulation of thyroidal glucose oxidation and *32P incorporation. Increased glucose oxidation in dog thyroid slices was observed when the gland was removed after the intracarotid injection of Nal. Under these conditions, stimulation of glucose oxidation by TSH in vitro was again inhibited, whereas LATS effect was either unaltered or augmented. These data suggest qualitative and/or quantitative difference(s) in TSH- as opposed to LATS-induced effects on thyroidal intermediary metabolism.