THE EFFECTS OF CERTAIN ANTITHYROID DRUGS ON THE UPTAKE OF RADIOACTIVE IODINE BY THE FROG THYROID

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Abstract
The iodine-concn. of the thyroid gland, as measured by the uptake of radioactive iodine (I131), was depressed in frogs (Rana pipiens, Rana clamitans and Rana palustris) injected with thiourea, sulfanilamide and KSCN. Subcut. injn. of 0.5 cc. of a 10% soln. of thiourea and of sulfanilamide, and 1 cc. of a 0.2% soln. of KSCN into normal frogs resulted in an enlarged, hyperemic and hyperplastic thyroid gland. Inhibition was most pronounced with thiourea, sulfanilamide and KSCN following in that order. Injected KSCN was rapidly removed from the blood stream, and its elimination was practically complete in 24 hrs. However, the iodine-concentrating capacity of the thyroid gland, as measured by the uptake of I131, was depressed by KSCN, provided a high concn. of the drug was still present in the circulation. After 24 hrs. the enlarged thyroids of the KSCN-treated frogs had a greater capacity than normal for absorbing I131.