ON THE IN VITRO ACCUMULATION OF INORGANIC IODIDE BY SURVIVING THYROID TISSUE WITH RADIOACTIVE IODINE AS INDICATOR1

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Abstract
Surviving thyroid slices were incubated at 38[degree] in a bicarbonate-Ringer soln. containing radioactive iodide as indicator. The amts. of I131 that entered the slices were compared with the amts. of I131 organically bound within the slices. Cyanide and sulfide, in addition to completely inhibiting the formation of thyroxine and diiodo- tyrosine, markedly depressed the accumulation of I131 by thyroid slices. Despite the almost complete inhibition of throxine and diiodotyrosine formation by 10-3 M azide, as much as 60% of the Ringer''s I131 entered the slices. Sulf-anilamide, which strongly inhibited the in vitro conversion of Ringer''s iodide to thyroxine and diiodotyrosine, had little effect on the iodine-concentrating capacity of thyroid tissue. It is concluded that in thyroid tissue there exists a mechanism for concentrating iodine that does not depend upon the conversion of inorganic iodine to thyroxine and diiodotyrosine.