Halpern J, Hinkle P M
Endocrinology. 1984 Jul;115(1):95-101. doi: 10.1210/endo-115-1-95.
T3 caused a dose-related increase in the rate of [3H]uridine uptake into GH4C1 rat pituitary tumor cells. T3 increased uridine uptake to 130-180% of the control value, with a half-maximal effect at approximately 1 nM. T3 exerted a half-maximal effect at 1 h and a maximal effect at 2 h. In contrast, epidermal growth factor also increased uridine uptake by 75%, with an ED50 of 0.6 ng/ml (0.1 nM), but a half-maximal response required 4 min and a maximal effect required 20 min. T3 increased the rate of uptake at all uridine concentrations from 30 nM to 130 microM. Equilibrium binding of [125I]T3 to nuclear receptors required from 15 min at 50 nM [125I]T3 to 1 h at 0.5 nM, indicating that occupancy of nuclear receptors precedes maximal stimulation of uridine uptake. T3 did not stimulate the rate of uridine uptake at 20 C, when binding to nuclear receptors does not occur. Various thyroid hormones caused an increase in uridine uptake, with the rank order of potency 3,3',5-triiodothyroacetic acid greater than T3 greater than L-T4 greater than D-T4 approximately equal to 3,3',5,5'-tetraiodothyroacetic acid; rT3 was inactive. This order parallels the affinities of these compounds for nuclear thyroid hormone receptors.
三碘甲状腺原氨酸（T3）使[3H]尿苷摄取到GH4C1大鼠垂体瘤细胞的速率呈剂量依赖性增加。T3将尿苷摄取增加至对照值的130 - 180%，在约1 nM时产生半数最大效应。T3在1小时时产生半数最大效应，在2小时时产生最大效应。相比之下，表皮生长因子也使尿苷摄取增加75%，半数有效剂量（ED50）为0.6 ng/ml（0.1 nM），但半数最大反应需要4分钟，最大效应需要20分钟。在30 nM至130 μM的所有尿苷浓度下，T3均增加摄取速率。[125I]T3与核受体的平衡结合，在50 nM [125I]T3时需要15分钟，在0.5 nM时需要1小时，这表明核受体的占据先于尿苷摄取的最大刺激。当在20℃时不发生与核受体结合时，T3不刺激尿苷摄取速率。各种甲状腺激素均导致尿苷摄取增加，其效力顺序为：3,3',5 - 三碘甲状腺乙酸＞T3＞L - T4＞D - T4≈3,3',5,5' - 四碘甲状腺乙酸；反式三碘甲状腺原氨酸（rT3）无活性。该顺序与这些化合物对核甲状腺激素受体的亲和力平行。
