Vitamin A Research Today is a free monthly online journal that collates and summarizes the latest research about Vitamin A, including details on retinol, benefits, dosage, supplements, deficiency, information. | ||||||||
|
Retinol has specific effects on binding of thyrotrophin to cultured porcine thyrocytes.Fröhlich E, Witke A, Czarnocka B, Wahl R Medical Clinic, Department of Endocrinology, Metabolism and Pathobiochemistry, Otfried-Muellerstrasse 10, D-72076 Tuebingen, Germany. 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. Published 13 December 2004 in J Endocrinol, 183(3): 617-26.
© 2004-2008 Vitamin A Research Today. All Rights Reserved. |
| ||||||
