Hinkle P M, Goh K B
Endocrinology. 1982 May;110(5):1725-31. doi: 10.1210/endo-110-5-1725.
The effects of physiological concentrations of L-T3 (T3) were examined in dispersed cell cultures of pituitaries obtained from 10- to 12-day-old rats. T3 inhibited TSH secretion by 50% and blunted the TSH response to TRH. The PRL response to TRH was also inhibited by T3, and GH secretion was increased 2-fold. These responses were half-maximal at 0.1 nM added T3 in medium supplemented with 10% hypothyroid calf serum, corresponding to a free T3 concentration of 5 pM. In the presence or absence of added T3, TRH effects were half-maximal at 0.5-3 nM, and T3 suppression was not overcome by high concentrations of TRH (up to 1 microM). Maximal inhibition of TSH responses to TRH occurred when cultures were preincubated with thyroid hormone for 24 h; a significant effect was observed after 8 h. The specific binding of [3H]TRH to dispersed rat pituitary cells was decreased 55-70% by T3 in a dose-dependent manner. Inhibition of TSH secretion by T3 was reversible within 24 h, and the fraction of thyrotrophs in the cultures (0.22) was not altered by T3 over the course of the experiments. The results demonstrate that physiological concentrations of T3 regulate TSH and PRL responses to TRH and control TRH receptor levels by a direct action on normal rat pituitary cells.
在取自10至12日龄大鼠的垂体分散细胞培养物中，研究了生理浓度的L-三碘甲状腺原氨酸（T3）的作用。T3可抑制促甲状腺激素（TSH）分泌达50%，并减弱TSH对促甲状腺激素释放激素（TRH）的反应。T3还抑制PRL对TRH的反应，而生长激素（GH）分泌增加了2倍。在添加10%甲状腺功能减退小牛血清的培养基中，添加0.1 nM T3时这些反应达到半数最大效应，对应游离T3浓度为5 pM。无论是否添加T3，TRH效应在0.5 - 3 nM时达到半数最大效应，高浓度TRH（高达1 μM）也不能克服T3的抑制作用。当培养物用甲状腺激素预孵育24小时时，TSH对TRH的反应受到最大抑制；8小时后观察到显著效应。[3H]TRH与大鼠垂体分散细胞的特异性结合被T3以剂量依赖性方式降低了55 - 70%。T3对TSH分泌的抑制在24小时内是可逆的，并且在实验过程中，培养物中促甲状腺细胞的比例（0.22）未被T3改变。结果表明，生理浓度的T3通过对正常大鼠垂体细胞的直接作用来调节TSH和PRL对TRH的反应，并控制TRH受体水平。
