Dual effects of iodide IV on reduced pyridine nucleotides in rabbit thyroid in situ: iodide induces oxidation and prevents oxidative response to thyrotropin.

Abstract

The redox state of pyridine nucleotides was continuously recorded with an organ-microfluorometer in the rabbit thyroid in situ. Intravenous sodium iodide, 0.5 to SO mg, caused a prompt, sustained, and roughly doserelated oxidation. A similar iodide effect was demonstrated in the rat thyroid and to a lesser degree in the rat testis, whereas the rat liver and the rabbit parathyroid were unresponsive. Thyrotropin had been shown in a preceding paper to cause a similar oxidative response in the thyroid. The iodide treatment, immediately or 12 hr prior to the thyrotropin administration, blocked the effect of this hormone. By contrast, thyrotropin had no significant effect on the action of iodide. Both of these iodide effects (oxidation of thyroid pyridine nucleotides and prevention of the thyrotropin effect), but not the thyrotropin effect, were abolished by perchlorate, whether this anion was given before or after the iodide load. These data indicate that iodide, while it produces an oxidative response in thyr...