Modulation of thyroglobulin messenger RNA level by thyrotropin in cultured thyroid cells

To examine the influence of thyrotropin (TSH) on the thyroglobulin (Tgb) mRNA content, the latter was evaluated in the cytoplasm of hog thyroid cells cultured in the absence (control cells) or presence of TSH. The Tgb mRNA levels were determined by, (i) kinetics of hybridization to sheep Tgb cDNA, (ii) capacity of coding for peptides immunologically related to Tgb in reticulocyte lysate. In cells cultured for 4 days in the absence of TSH, the content of Tgb mRNA sequences decreased to 30% of its initial value and the messenger activity to 15%. Conversely, TSH maintained the initial Tgb mRNA level in cells cultured in its presence, and TSH concentrations 50 micronU/ml or 5 mU/ml gave identical results. At each period tested poly (A) content was the same in TSH-treated and control cells. When TSH was added to media after 4 or 8 days culture without TSH, the Tgb mRNA level was partially restored. These results suggest that TSH exerts a positive control on Tgb gene expression through modulation of Tgb mRNA content of thyroid cells.