Effects of Thyroxine and KSCN on Capacity of Rat Thyroid Gland to Accumulate Astatine 211 . ∗

Summary

1. The administration of thyroxine to the intact female Sprague-Dawley rat resulted in a lowered thyroidal accumulation of both At²¹¹ and I¹³¹. Since it is known that thyroxine inhibits production of TSH by the pituitary gland, it is suggested that a reduced pituitary function resulted in a reduced thyroidal accumulation of both halogens. It is further indicated that the thyroidal accumulation of At²¹¹ is under pituitary control. 2. It has been demonstrated that thiocyanate blocks the thyroidal accumulation of astatide, and that since thiocyanate can discharge At²¹¹ from the thyroid gland, At²¹¹ probably is not organically bound in a manner similar to the organic binding of I¹³¹.