三碘甲状腺乙酸在培养的垂体前叶细胞中的摄取及其对促甲状腺激素分泌的影响。

Uptake of triiodothyroacetic acid and its effect on thyrotropin secretion in cultured anterior pituitary cells.

作者信息

Everts M E, Visser T J, Moerings E P, Docter R, van Toor H, Tempelaars A M, de Jong M, Krenning E P, Hennemann G

机构信息

Department of Internal Medicine, Erasmus University Medical School, Rotterdam, The Netherlands.

出版信息

Endocrinology. 1994 Dec;135(6):2700-7. doi: 10.1210/endo.135.6.7988460.

DOI:10.1210/endo.135.6.7988460

PMID:7988460

Abstract

The uptake of [125I]triiodothyroacetic acid ([125I]Triac) in anterior pituitary cells was investigated and compared with that of [125I]T3. Furthermore, the effects of Triac, T3, and T4 on TSH release were compared. Cells isolated from adult male Wistar rats were cultured for 3 days in medium with 10% fetal calf serum. Uptake was measured at 37 C with [125I]Triac (100,000 cpm; 120 pM) or [125I]T3 (50,000 cpm; 50 pM) in medium with 0.5% BSA. In this medium, the ratio of the free fractions of Triac, T3, and T4 was 1:8:1. Exposure of cells to 100 nM TRH for 2 h stimulated TSH release by 80-110% (P < 0.001). Comparing total hormone levels (1 nM to 1 microM), Triac and T3 were equally effective in reducing this response, and both were 10-fold more effective than T4. The time course (15 min to 4 h) of [125I]Triac uptake was similar to that of [125I]T3, showing equilibrium after 1 h. Unlabeled Triac (1 microM) reduced the uptake of [125I]Triac and [125I]T3 at all time intervals. Expressed per pM free hormone, the cellular and nuclear uptake of [125I]Triac were twice those of [125I]T3. The 15-min uptake of [125I]Triac was reduced by incubation with 10 nM unlabeled Triac (35%; P < 0.001). Maximum inhibition (56%; P < 0.001) was found with 10 microM Triac. A similar effect was seen with 10 microM T3, T4, or 3,3',5,5'-tetraiodothyroacetic acid. Preincubation (30 min) and incubation (15 min) with 10 microM oligomycin reduced the cellular ATP content by 51% (P < 0.001), [125I]T3 uptake by 77% (P < 0.001), and [125I]Triac uptake by only 25% (P < 0.001). The temperature dependence of [125I]Triac and [125I]T3 uptake was the same. Preincubation and incubation with 10 microM monensin (reduces the Na+ gradient) or 10 microM monodansylcadaverine (inhibits receptor-mediated endocytosis) reduced 15-min [125I] Triac uptake by 15% (P < 0.005) and 19% (P < 0.005), respectively. The data show that 1) Triac, on the basis of the free hormone concentration, is more potent than T3 or T4 in suppressing TSH secretion; and 2) the rapid uptake of [125I]Triac by the anterior pituitary occurs by a carrier-mediated mechanism that is only partially dependent on ATP or the Na+ gradient.

摘要

研究了成年雄性Wistar大鼠垂体前叶细胞对[125I]三碘甲状腺乙酸（[125I]Triac）的摄取，并与[125I]T3的摄取进行比较。此外，还比较了Triac、T3和T4对促甲状腺激素（TSH）释放的影响。从成年雄性Wistar大鼠分离的细胞在含10%胎牛血清的培养基中培养3天。在37℃下，用含0.5%牛血清白蛋白（BSA）的培养基中的[125I]Triac（100,000计数/分钟；120皮摩尔）或[125I]T3（50,000计数/分钟；50皮摩尔）测量摄取量。在该培养基中，Triac、T3和T4的游离部分比例为1:8:1。将细胞暴露于100纳摩尔促甲状腺激素释放激素（TRH）2小时可刺激TSH释放增加80 - 110%（P < 0.001）。比较总激素水平（1纳摩尔至1微摩尔）时，Triac和T3在降低这种反应方面同样有效，且两者的效力均比T4高10倍。[125I]Triac摄取的时间进程（15分钟至4小时）与[125I]T3相似，1小时后达到平衡。未标记的Triac（1微摩尔）在所有时间间隔均降低了[125I]Triac和[125I]T3的摄取。以每皮摩尔游离激素表示，[125I]Triac的细胞摄取和核摄取是[125I]T3的两倍。与10纳摩尔未标记的Triac孵育可使[125I]Triac的15分钟摄取量降低35%（P < 0.001）。10微摩尔Triac时抑制作用最大（56%；P < 0.001）。10微摩尔T3、T4或3,3',5,5'-四碘甲状腺乙酸也有类似作用。用10微摩尔寡霉素预孵育（30分钟）和孵育（15分钟）可使细胞ATP含量降低51%（P < 0.001），[125I]T3摄取量降低77%（P < 0.001），而[125I]Triac摄取量仅降低25%（P < 0.001）。[125I]Triac和[125I]T3摄取的温度依赖性相同。用10微摩尔莫能菌素（降低Na+梯度）或10微摩尔单丹磺酰尸胺（抑制受体介导的内吞作用）预孵育和孵育分别使[125I]Triac的15分钟摄取量降低15%（P < 0.005）和19%（P < 0.005）。数据表明：1）基于游离激素浓度，Triac在抑制TSH分泌方面比T3或T4更有效；2）垂体前叶对[125I]Triac的快速摄取通过载体介导机制发生，该机制仅部分依赖于ATP或Na+梯度。