Endocrine Abstracts

The purpose of this work was to investigate the effect of thyrotropin (TSH) on the thyroglobulin and on the polypeptides distribution in primary cultures of human thyroid cells.

Thyroid cells isolated from cold nodules (follicular adenoma) were cultured for 5 to 8 days in the presence of 0.05 to 25 mU/ml of TSH (TSH cells) or in the absence of the hormone (control cells). After homogenization of the cells, thyroglobulin radioimmunoassay was performed. The amount of thyroglobulin extracted from the thyroid cells particles, recovered in the soluble fraction and released in the medium was specifically increased by TSH. In a sucrose gradient, the thyroglobulin related antigens of the soluble fraction sedimented mainly at 19S and 12S. However, in TSH cells, the 19S/12S ratio was increased. After fractionation of the soluble proteins by polyacrylamide gel electrophoresis in denaturating conditions, two bands (320 and 250 molecular mass) characteristic of human purified thyroglobulin were detected. In addition, a large group of heterogeneous proteins (425-50 molecular mass) was found. TSH induced several modifications in this group of polypeptides, the most striking one being a drastic increase in an 80 molecular mass compound. This last material was also found in the solubilized particulate fraction of the cells, suggesting that it may represent newly synthetized polypeptides.

TSH increases the thyroglobulin content in the culture medium and in the cells isolated from follicular adenoma. Control and TSH treated cells exhibit the two major bands of human purified 19S thyroglobulin. In addition, TSH cells show several modifications with particularly an increase in an 80 molecular mass polypeptide.