Characterization of a 1,25-dihydroxy-vitamin D3 receptor in FRTL-5 cells. Evidence for an inhibitory effect of 1,25-dihydroxy-vitamin D3 on thyrotropin-induced iodide uptake.
When FRTL-5 cell cytosol was incubated with increasing amounts of [3H]1,25-dihydroxy-vitamin D3 [( 3H]1,25-(OH)2D3), saturation of specific hormone binding occurred. Scatchard analysis of specific binding of [3H]1,25-(OH)2D3 to the macromolecule yielded an apparent Kd value of 0.41 +/- 0.08 X 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)2D3 association with a macromolecule sedimentating slightly faster than ovalbumin (3.7 S). [3H]1,25-(OH)2D3 was completely displaced by excess 1,25-(OH)2D3. The 1,25-(OH)2D3-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)2D3 receptor in thyroid follicular cells. Furthermore, 1,25-(OH)2D3 inhibited the thyrotropin (TSH)-stimulated iodide uptake in a dose-dependent manner, indicating that 1,25-(OH)2D3 has an effect on the physiological function of rat thyroid follicular cells in culture.
Lamberg-Allardt
C
C
Endocrine Research Laboratory, University of Helsinki, Finland.
Valtonen
E
E
Polojärvi
M
M
Stewen
P
P
D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002460:Cell Line; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects; D007454:Iodides / Q000378:metabolism*; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000737:chemistry* / Q000302:isolation & purification; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects*; D013972:Thyrotropin / Q000378:metabolism*; D014807:Vitamin D / Q000031:analogs & derivatives
D007454:Iodides; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D014807:Vitamin D; D013972:Thyrotropin; D002117:Calcitriol