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A Shiroozu

Publications and source records attributed to A Shiroozu.

22 records · Page 2Linked to original sources
PubMed1979

Iodoamino acid synthesis in thyroid lobes in vitro with excellent yield of iodothyronines.

Thyroid lobes of male Sprague-Dawley rats on an iodine-sufficient diet were incubated in our improved in vitro system with 0.01 microM 127I and 5mU/ml of bovine TSH. Thyroidal 131I-uptake and the relative incorporation of iodine into iodothyronines increased with time. The average yield of each iodoamino acid after 8 h of incubation was: monoiodotyrosine 28.0%, diiodotyrosine 46.5%, triiodothyronine 1.9% and thyroxine 13.9%, which showed a striking resemblance to the values obtained in vivo. The yields of iodotyrosines and iodothyronines, the latter in particular, were strikingly high, and this system is considered to be useful in the study of thyroidal iodine metabolism. Effects of TSH, temperature and pH of the medium were examined and a unique effect of pH was observed on the iodoamino acid synthesis. As the pH was elevated from 6.8 to 7.9, 131I-uptake, MIT/DIT ratio, T4/DIT ratio and T3/T4 ratio increased. The effect of slightly alkaline pH was considered to be similar to that observed in iodine-deficiency. It was found that the rubber stoppers which are commonly used in short-term incubation contain a kind of potent inhibitor of thyroid hormone synthesis. The pattern of inhibition was similar to that of thionamide compounds.

Animals↗
PubMed1978

Chemical determination of iodinated compounds in human thyroid.

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.

Adult↗