THE ACTION OF VARIOUS GOITROGENS IN INHIBITING LOCALIZATION OF RADIOIODINE IN THE THYROID AND THYMUS GLANDS OF LARVAL TREE TOADS

¹ Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tenn., Department of Biology, The Catholic University of America, Washington 17, D. C., and Department of Biology, The University of Virginia, Charlottesville, Virginia

1. Larvae of Hyla versicolor were immersed for 15 days in spring water containing phenylthiourea, KClO₄, KSCN, KClO₃, or KIO₃ followed by a 24-hour immersion in 20 µc./ml. of I¹³¹, a thyroid-destroying dose.

2. When treatment with any one of these drugs was continued during the period of I¹³¹ administration, radiation damage to the thyroid was prevented.

3. The inhibitory effect of KClO₄ on the thyroid persisted even when treatment was discontinued two days before immersion in the I¹³¹ solution.

4. The effects of phenylthiourea and KSCN were dissipated more quickly since the thyroid showed extensive damage when treatment was stopped immediately before I¹³¹ administration and complete destruction when it was stopped two days before.

5. In control animals, the thyroid-destroying dose of I¹³¹ extensively damaged the thymus gland as well.

6. Of the drugs tested, only KClO₄ sufficiently inhibited the I¹³¹ uptake by the thymus to prevent damage, and only when it was present during the period of exposure to I¹³¹.