As a tool with which to detect iodinated compounds in human thyroid specimens, we have reevaluated a nonincineration technique which has so far been employed in the determination of thyroxine-iodine in peripheral blood.
The catalytic action of iodoamino acids in the Ce-As reaction was enhanced by a small amount of Cl₂. On the contrary, a large amount of Cl₂ inhibited the reaction unexpectedly. Among iodide, iodotyrosine and iodothyronine, iodide was the most effective catalyst in the Ce-As reaction and iodothyronine was the least effective one. Protein seemed to inhibit this reaction of thyroglobulin. But the result of iodine content in thyroglobulin by this technique agreed well with that by incineration when measured ¹²⁷I wascorrected by percent activity of dializable part of the total activity of ¹³¹I-thyroglobulin with the same protein concentration, after the NaClo treatment.
The results of human thyroid specimens were as follows: the thyroglobulin content of five normal subjects was 8.0±1.5% of wet thyroid weight. That of Hashimoto's disease was significantly decreased which seemed compatible with the decrease in iodine content of thyroglobulin, whereas thyroglobulin content of Graves disease treated with 1-methyl, 2-mercaptoimidazole followed by a large dose of iodide was well preserved in spite of a lower degree of iodination of thyroglobulin. As for the distribution of iodoamino acids-iodine in normal thyroid, T₄ was 20.5±0.7%.
This technique ultimately looks promising as a tool with which to study intrathyroidal iodine metabolism in human.