ABSTRACT
The content and distribution of iodoamino acids in thyroglobulin of the cryopreserved thyrotoxically-changed thyroid parenchyma were studied, as was thyroglobulin iodination. Thyroid tissue obtained during operations of patients with diffuse-toxic goiter was investigated. The thyroid parenchyma was cryopreserved according to the method developed at the Institute of Cryobiology and Cryomedicine Problems, Academy of Sciences of the Ukrainian SSR. The tissues were stored for 4-6 months. Thyroglobulin was isolated by gel filtration of the thyroid saline extract through a column packed with Sephadex G-200. Thyroglobulin was iodinated with KI + I2 water solution, pH 9.2, at 37 C for 30 min. The amount of iodine added was 100 moles of I2 per protein mole. Protein concentration was determined by the biuret reaction. Thyroglobulin iodoamino acid composition was determined by direct spectrophotometry. Absorption spectra were measured by an EPS-3T recording spectrophotometer ("Hitachi", Japan). The processes of freezing (-196 degrees C) and thawing of the thyroid parenchyma were shown to induce no changes in the thyroglobulin iodoamino acid composition. Cryopreservation of the thyroid parenchyma considerably affected iodine incorporation and formation of iodoamino acids in the thyroglobulin during its in vitro iodination. It may be supposed that cryopreservation of the thyroid tissue affects the thyroglobulin conformational status, that results in increased iodination of this iodoprotein.
