Iodine Compounds in Plasma of Rats: Effect of Exposure to High Environmental Temperature

Abstract

THE rate of release of iodine-131 from the thyroid has been widely used as an index for thyroid activity and has been considered a reliable index for thyroid function¹. It is also used as a basis for the rate of secretion of thyroxine (TSR) by the replacement method². Recently, this laboratory³ reported a higher rate of release of iodine-131 from the thyroid in rats following long-term exposure to a high environmental temperature (34° C). These findings prompted the question whether the composition of the substance(s) released might be constant in different physiological conditions; that is, would long-term exposure to environmental heat alter the composition of the iodinated compounds which were released by the thyroid gland? This experiment was undertaken in order to determine the nature of the iodinated compounds in plasma of rats during exposure to heat (34° C).