Characterization of a 1,25-dihydroxy-vitamin D 3 receptor in FRTL-5 cells. Evidence for an inhibitory effect of 1,25-dihydroxy-vitamin D 3 on thyrotropin-induced iodide uptake

• Published in: Molecular and cellular endocrinology Vol. 81; no. 1; pp. 25 - 31
• Main Authors: Lamberg-Allardt, C., Valtonen, E., Polojärvi, M., Stewen, P.
• Format: Journal Article
• Language: English
• Published: Elsevier Ireland Ltd 1991
• Subjects: 1,25-Dihydroxy-vitamin D 3; FRTL-5 cells; Iodide uptake; Thyrotropin; 1,25-Dihydroxy-vitamin D 3; FRTL-5 cells; Thyrotropin; Iodide uptake
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/0303-7207(91)90201-3

When FRTL-5 cell cytosol was incubated with increasing amounts of [ 3H]1,25-dihydroxy-vitamin D 3 ([ 3H]1,25-(OH) 2D 3), saturation of specific hormone binding occurred. Scatchard analysis of specific binding of [ 3H]1,25-(OH) 2D 3 to the macromolecule yielded an apparent K dvalue of 0.41 ± 0.08 × 10 −10 M and a single maximum binding capacity of 42.8 ± 8.8 fmol/mg protein. Sucrose gradient analysis revealed substantial [ 3H]1,25-(OH) 2D 3 association with a macromolecule sedimentating slightly faster than ovalbumin (3.7 S). [ 3H]1,25-(OH) 2D 3 was completely displaced by excess 1,25-(OH) 2D 3. The 1,25-(OH) 2D 3-receptor complex bound to DNA cellulose columns in low salt buffer, and eluted as a single peak at 0.15–0.20 M KCl. Thus, we have shown for the first time the existence of a functional 1,25-(OH) 2D 3 receptor in thyroid follicular cells. Furthermore, 1,25-(OH) 2D 3 inhibited the thyrotropin (TSH)-stimulated iodide uptake in a dose-dependent manner, indicating that 1,25-(OH) 2D 3 has an effect on the physiological function of rat thyroid follicular cells in culture.