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 was corrected 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.