BINDING OF I-125 LABELED THYROTROPIN TO TRANSFECTED HUMAN THYROCYTES (SGHTL-34 CELLS)

The binding of 125I-labelled bovine TSH to a human thyroid cell line (SGHTL-34) has been studied. Binding to hormonally responsive cells was time dependent, specific and reversible. Scatchard analysis of the binding data indicated the presence of a single binding site with high affinity (intrinsic dissociation constant (K(d)) = 0.25 ± 0.08 nmol/l; mean ± S.E.M.; n = 4) and low capacity (maximum binding (B(max)) = 104 ± 29 fmol/mg protein, mean ± S.E.M.; n = 4). Hill plots confirmed the presence of a single site. Kinetic data demonstrated close agreement between the K(d) and B(max) obtained from the competition data (K(d) = 0.23 ± 0.35 nmol/l; B(max) = 161 ± 83 fmol/mg protein; n = 6).