A Comparison of the Effects of Thyrotrophin and Sodium Iodide on the Oxidation of Glucose-l-14C and the Levels of Triphosphopyridine Nucleotides in Thyroid Slices from Several Species

Abstract

The comparative effects of sodium iodide and TSH, in vitro, upon the oxidation of glucose-l-¹⁴C and upon triphosphopyridine nucleotide levels in slices of dog, rat, beef and sheep thyroid glands are reported. While TSH increased glucose oxidation in all these species, Nal, in concentrations of 1 × lO^-3M and 1 × 1O^-4M, produced consistent and statistically significant stimulation only in sheep thyroid slices. In the sheep, the effect of Nal in Krebs-Ringer phosphate buffer was equivalent to that of TSH. The levels of TPN in dog and beef thyroid incubated in Krebs- Ringer bicarbonate buffer were increased when TSH was added to the medium, while the changes attributable to Nal were inconstant. In sheep thyroid slices the changes in TPN in the presence of both TSH and Nal were small and inconstant even in those experiments in which there was a clear-cut stimulation of glucose oxidation. It was concluded that the effect of TSH upon glucose oxidation in thyroid slices is not mediated by TSH-induced release of iodide from the thyroid, since, in several species, TSH increased glucose oxidation when Nal had no effect. It was not possible to demonstrate that Nal stimulation of glucose oxidation in sheep thyroid slices was mediated through an acceleration of TPNH oxidation. (Endocrinology75: 711, 1964)