Effect of thyrotropin on the properties of messenger RNA from cultured human thyroid cells

When added to the culture medium of thyroid cells isolated from diffuse nontoxic goiter, thyrotropin increased the poly(adenylic acid) content and the template activity of the unfractionated RNA. This increase was correlated with higher thyroglobulin messenger activity, as demonstrated by specific immunoprecipitation of the labeled peptides synthesized in two heterologous cell-free systems. When RNAs were separated in a sucrose gradient, thyrotropin was shown to enhance the poly(adenylic acid) content and template activity of fractions with sedimentation coefficients of 34, 23 and 15 S. Specific immunoprecipitation showed that a thyroglobulin messenger activity was present in these three fractions. Another way by which thyrotropin regulates the thyroid protein synthesis is suggested by the shift of poly(adenylic acid)-containing RNA to large polysomes when thyroid cells were cultured in the presence of the hormone.