EFFECTS OF INORGANIC IODIDE ON THE INTERMEDIARY CARBOHYDRATE METABOLISM OF SURVIVING SHEEP THYROID SLICES*

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Abstract
Enrichment of incubation media with increasing concentrations of inorganic iodide induced pronounced and biphasic alterations in the oxygen consumption and glucose metabolism of sheep thyroid slices. Moderate concentrations of iodide (up to 1 x 10-4 [image]) enhanced both QO2 and the generation of C14O2 from glucose-U-C14, -1-14, and -6-C14. At high concentrations of added iodide (5 x 10 -2 [image]), stimulation of these functions was diminished or absent. The stimulatory effects of moderate concentrations of iodide appeared to be related to the oxidation or organisation of increased quantities of iodine for the following reasons 1) stimulatory effects were inhibited by methimazole and thiouracil, 2) bromide failed to stimulate thyroidal oxidations, and 3) no stimulation of oxidations was evident in slices of liver or kidney. It is postulated that the stimulatory effects of iodide on glucose oxidation of reduced coenzymes that may occur during both the oxidation of iodide and its subsequent reduction. The loss of metabolic stimulation occurring at higher concentrations of iodide is of uncertain origin, but may be related, as either cause or effect, to the inhibition of thyroid hormone formation that high concentrations of thyroidal iodide acutely induce.