title: Retinol has specific effects on binding of thyrotrophin to cultured porcine thyrocytes.
abstract: Retinoids are potential candidates for the treatment of thyroid cancer. However, one of the disadvantages of these substances is their dedifferentiating effect on normal non-transformed thyrocytes. To identify conditions under which no dedifferentiating effect of retinol on normal thyrocytes can be observed, we determined iodide uptake, protein iodination, expression of sodium-iodide symporter (NIS) mRNA and protein, and the binding of iodine-125-labelled bTSH in cultured porcine thyrocytes. Combination of TSH and < or =6.5 microM retinol increased iodide uptake and protein iodination compared with TSH alone over the entire incubation time, whereas TSH plus > or =13 microM retinol increased the uptake of iodine-125 only during the first 12 h but decreased it after 30 h and longer. After > or =30 h incubation times with > or =13 microM retinol, the fraction of apoptotic cells was enhanced and proliferation decreased. The incubation with retinol enhanced the binding of [125I]bTSH to thyrocytes, but did not influence expression of the NIS. With low retinol concentrations, the effect on the binding of TSH apparently predominated and retinol increased thyroid function; with higher concentrations the pro-apoptotic effect of retinol overlapped and a two-phased time course resulted. It can be concluded that low concentrations of retinol also exert differentiating effects in normal thyrocytes.
authors.affiliation: Medical Clinic, Department of Endocrinology, Metabolism and Pathobiochemistry, Otfried-Muellerstrasse 10, D-72076 Tuebingen, Germany.
authors.forename: Eleonore
authors.initials: E
authors.lastname: Fröhlich
authors.forename: Anja
authors.initials: A
authors.lastname: Witke
authors.forename: Barbara
authors.initials: B
authors.lastname: Czarnocka
authors.forename: Richard
authors.initials: R
authors.lastname: Wahl
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D007150:Immunohistochemistry / Q000379:methods; D007454:Iodides / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D013552:Swine; D027981:Symporters / Q000235:genetics / Q000378:metabolism; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*; D013972:Thyrotropin / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors; D014801:Vitamin A / Q000494:pharmacology*; D000099209:Sodium-Iodide Symporters
chemical_list: D007454:Iodides; D007457:Iodine Radioisotopes; D012333:RNA, Messenger; D027981:Symporters; D013972:Thyrotropin; D014801:Vitamin A; D000099209:Sodium-Iodide Symporters