Presence of epidermal growth factor receptors on human thyroid membranes

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Abstract
The nature of epidermal growth factor (EGF) receptors in normal and pathological thyroid membranes was studied on a crude membrane fraction (10,000 .times. g pellet) of tissue homogenate. Optimal binding of 125I-EGF to human thyroid membranes was obtained at 25.degree. C with 1-h incubation at pH 7.4. The study revealed the presence of both high and low affinity receptors in normal and pathological thyroid membranes. The association constants of high affinity receptor (3.2 .times. 10-9 mol/l) and of low affinity receptor (1.8 .times. 10-8 mol/l) observed in normal thyroid membranes were similar to those of thyroid membranes from neoplastic as well as thyrotoxic thyroid tissues. [3H]thymidine incorporation into DNA of cultured human thyroid cells was stimulated by EGF in a dose-dependent manner. A half-maximal stimulation was found around 1 .times. 10-10 mol/l. These results suggest the EGF may have a possible role in the regulation of thyroid growth and function in physiological and pathological situations.