Thyrotropin modulates EGF receptor function in porcine thyroid follicle cells

Area of Science:

• Endocrinology
• Cell Biology
• Molecular Biology

Background:

• Thyroid follicle cells play a crucial role in hormone production.
• Epidermal Growth Factor (EGF) is a potent mitogen.
• The interaction between EGF and thyroid cells requires further investigation.

Purpose of the Study:

• To characterize high-affinity EGF receptors in porcine thyroid follicle cells.
• To investigate the modulatory effects of Thyroid-Stimulating Hormone (TSH) on EGF receptor expression and function.
• To elucidate the role of cyclic AMP (cAMP) in TSH-mediated modulation of EGF responsiveness.

Main Methods:

• Monolayer and suspension cultures of porcine thyroid follicle cells.
• Binding assays using radiolabeled EGF ([125I]EGF).
• Scatchard analysis to determine receptor characteristics.
• Measurement of [3H]thymidine incorporation to assess mitogenic activity.
• Treatment with TSH, cholera toxin, dibutyryl cAMP, and forskolin.

Main Results:

• Porcine thyroid follicle cells possess a single class of high-affinity EGF receptors (Kd = 4.5 X 10(-10) M).
• TSH and other cAMP-elevating agents significantly increased EGF receptor number in suspension cultures.
• TSH and cholera toxin pre-treatment inhibited [3H]thymidine incorporation, an effect reversed by low EGF concentrations.
• Higher EGF concentrations potentiated [3H]thymidine incorporation in TSH- or cholera toxin-pretreated cells.

Conclusions:

• Porcine thyroid follicle cells express high-affinity EGF receptors.
• TSH modulates EGF receptor expression and responsiveness via a cAMP-dependent pathway.
• TSH influences both the inhibitory and mitogenic effects of EGF on thyroid follicle cells in vitro.