Thyroid albumin. II. In Vitro synthesis of a thyroid albumin by normal human thyroid tissue1

Slices from normal human thyroid tissue have been incubated with labeled amino acids in a modified Krebs-Ringer-bicarbonate buffer for various lengths of time up to 12 hr. The soluble proteins from the incubated tissue and eventually from the medium have been separated by gel filtration on Sephadex G-200 and chromatography on DEAE-Sephadex A50. A labeled protein has been purified which had gel filtration, chromatographic, electrophoretic, and immunological properties of albumin. Persistence of the label on the albumin after treatment by 8 M urea and uniform labeling of the several peptides obtained by CNBr hydrolysis demonstrated that amino acid incorporation corresponded with actual de novo synthesis of the albumin. In 2 successive experiments on 2 different glands, the ratio of thyroid albumin labeling vs. thyroglobulin labeling was 0.17 and 0.30. These values are of the same order of magnitude as the concentration ratios of 4S protein and thyroglobulin in human thyroid glands. The results of these in vitro studies suggest that at least a part of the iodinated albumin which may be extracted from normal thyroid glands is synthesized within the thyroid tissue itself. © 1971 by The Endocrine Society.SCOPUS: ar.j