STUDIES ON THE MECHANISM OF IODINE UPTAKE BY THYROID TISSUE

Abstract

To investigate each process of iodine uptake by thyroid tissue, experiments were performed under various conditions. Results obtained were as follows : 1) Accelerative effects of various inorganic salts, and inhibitory effects of sodium cyanide methylthiouracil and various plant components were observed in I131 uptake experiments with frozen thyroid tissue. 2) Inhibitory effect of methylthiouracil on the process of I131 binding by thyroid was observed. Its binding force became so weak that the bound form of I131 in thyroid slices was transformed into the liberated form by action of potassium rodanate, 3) The existence of coupling process of I131 to tyrosine molecules, loosely bound by some protein-like polymer in thyroid tissue was proved. Hypothesis of “bound tyrosine” was proved by using C14 tyrosine incorporation method. Inhibitory effects of sodium cyanide and methylthiouracil on the process of coupling I131 to “bound tyrosine” were observed. 4) I131 uptake by thyroid slices was more sensitively inhibited than their oxygen consumption under various conditions, such as replacement of incubation medium, addition of sodium cyanide, methylthiouracil, various plant components, and potassium iodide.