[Interaction of TSH with human plasma membranes from normals and diseased thyroid glands (author's transl)].

Binding of TSH to plasma membranes purified from normal human thyroid gland is specific, saturable and dependent upon temperature, time, pH and salt concentration (standard assay conditions: 27 degrees C, 30 min, pH 7.8, 20 mM Tris). Displacement curve of 125I-TSH by unlabelled TSH shows a curvilinear relationship between B/F and B which can be interpreted by the presence of two sites with apparent binding constants about 5 nM and 500 nM and capacities of about 3 and 30 pmol/mg membrane protein, respectively. Systematic study of binding characteristics of membranes from 6 normal glands, 7 euthyroid multinodular goitres, 14 Graves' goitres and 2 toxic nodules do not show difference in the dissociation constants and capacities of sites between normal and diseased thyroid and between nodular and perinodular tissue in toxic nodules.