TRANSPORT AND ACTIONS OF THYROID HORMONES

这项研究的长期目标是详细了解 甲状腺激素的作用机制。《公约》的具体目标 提案是定义甲状腺激素摄取到 并评估甲状腺激素发挥作用的可能性 它们通过核外作用对脑垂体细胞产生的一些影响。三 不同类型的初步数据表明，甲状腺激素 通过载体介导的转运进入垂体瘤细胞GH-细胞 系统。首先，生长激素细胞摄取L-三碘甲腺原氨酸(T3)可以 丹西卡维林、细胞松弛素b和氯喹对其抑制作用 密切相关的药物，如细胞松弛素d和e以及地丹西卡德维林。 第二，甲状腺激素的摄取明显依赖于温度。 这种方式与简单的扩散机制不一致。第三, 对T3转运的动力学分析揭示了一种饱和吸收机制。它 建议详细研究甲状腺激素的运输，分析 转运的动力学、底物专一性和能量依赖性 完整的细胞和分离的膜泡。甲状腺的假说 激素通过受体介导的内吞作用进入细胞将通过 比较罗丹明标记的和天然的T3的行为。甲状腺 激素转运蛋白(S)将通过重组成脂质体而分离出来 和光亲和标记。在生长激素细胞中，甲状腺激素诱导生长 激素和调节受体的浓度 促甲状腺激素释放激素及其量效曲线 不同的甲状腺激素的作用相差10到100倍 类比。来测试调节TRH受体的可能性 根据甲状腺激素的膜效应，将测量T3反应。 在膜泡和去核的生长激素细胞中。最后，为了尝试 评估甲状腺激素转运体的生理意义(S)和 生长激素细胞的激素、突变体可能的膜作用部位 不能运输甲状腺激素的人将选择使用T3-蓖麻毒素A 链，并进行了详细的表征。这些研究应该会增加我们的 了解一种重要的调节荷尔蒙的作用机制。

The long range objective of this research is a detailed understanding of the mechanism of action of thyroid hormones. The specific goals of the proposal are to define the mechanism of thyroid hormone uptake into pituitary cells and to evaluate the possibility that thyroid hormones exert some of their effects in pituitary cells by an extra-nuclear action. Three types of preliminary data suggest that thyroid hormones are transported into pituitary tumor cells, GH-cells, by a carrier mediated transport system. First, uptake of L-triiodothyronine (T3) into GH-cells can be inhibited by dansylcadaverine cytochalasin b and chloroquine but not by closely related drugs like cytochalasins d and e and didansylcadaverine. Second, thyroid hormone uptake is markedly temperature dependent in a manner that is inconsistent with a simple diffusional mechanism. Third, kinetic analysis of T3 transport reveals a saturable uptake mechanism. It is proposed to study thyroid hormone transport in detail, analyzing the kinetics, substrate specificity and energy dependence of transport into intact cells and isolated membrane vesicles. The hypothesis that thyroid hormones enter cells by receptor mediated endocytosis will be tested by comparing the behavior of rhodamine-labeled and native T3. The thyroid hormone transporter(s) will be isolated by reconstitution into liposomes and photoaffinity labeling. In GH-cells thyroid hormones induce growth hormone and regulate the concentration of receptors for thyrotropin-releasing hormone and the dose-response curves for these actions differ by factors of 10 to 100 for various thyroid hormone analogs. To test the possibility that regulation of TRH receptors results from a membrane effect of thyroid hormones, T3 responses will be measured in membrane vesicles and enucleated GH-cells. Finally, in an attempt to assess the physiological significance of thyroid hormone transporter(s) and possible membrane sites of action of the hormones, mutants of GH-cells unable to transport thyroid hormones will be selected using T3-ricin A chain and characterized in detail. These studies should add to our understanding of the mechanism of action of an important regulatory hormone.