Epidermal growth factor inhibits thyrotropin-mediated synthesis of tissue-specific proteins in cultured ovine thyroid cells.

Primary cultures of ovine thyroid cells were induced to differentiate by addition of thyrotropin (TSH). This was demonstrated as an accumulation of 2 thyroid-specific proteins, thyroglobulin and thyroid peroxidase, using immunofluorescent staining methods and immunoprecipitation of biosynthetically labeled cultures. As an additional measure of differentiation, cells exhibited a morphological response to TSH and regained the ability to incorporate radioactive iodide. Epidermal growth factor (EGF) markedly inhibited differentiation when added together with TSH. Thyroglobulin synthesis was reduced to low levels and peroxidase synthesis was reduced to levels that were undetectable by the methods used. Morphological changes in response to TSH were also diminished by EGF. The antagonistic interaction between TSH and EGF in regulating differentiation in cultured thyroid cells may reflect the type of control that exists in vivo.