REGULATION OF RENAL THYROID HORMONE UPTAKE & METABOLISM

这项建议的长远目标，是研究 调节外周组织对甲状腺素（T4）的摄取和代谢， 甲状腺的主要分泌产物，以及3，5，3 '- 三碘甲状腺原氨酸（T3），最有效的甲状腺激素以及其他 碘甲腺原氨酸代谢物。 这些研究将检查肾脏的作用， T3和T4的产生和组织区室化与循环。 以下将介绍与甲状腺激素摄取有关的三种一般现象： 在拟定研究中检查1）血管，2）细胞膜3） 细胞的或胞质的。 灌注肾系统，建立在这个 实验室，提供了研究其他甲状腺影响的机会 组织中 使用单程和再循环肾灌注， 调节细胞甲状腺激素流入和流出的机制将是 探讨了 细胞质和灌注液培养基中的游离甲状腺激素组分 将通过平衡透析测定。 的机制 将寻求甲状腺激素广泛的单通道肾摄取 与稳态组织甲状腺激素浓度相关， 代谢率 有了这些信息，动态吸收过程将 数学建模，以帮助区分吸收简单 游离激素扩散和易化或主动转运。 建模 在该系统中，易位过程的过程被大大简化， 参数如激素载体蛋白类型和浓度、配体 浓度、组织转运时间以及排泄和 可以控制代谢途径。 将采用这些技术 以区分肾流量和稳态分布的改变， 存在与甲状腺激素竞争的药物时的碘甲状腺原氨酸 与循环或细胞蛋白质结合。 光镜 将进行放射自显影以识别组织和细胞 肾甲状腺激素交换位点。 一项研究将探讨组织/灌注液区室化的差异 与T3衍生物相比，T4局部5 '-脱碘产生的T3 从循环。 体外5 '-脱碘酶抑制剂的作用， 与细胞激素结合竞争的药物，以及甲状腺状态的改变 将被审查。 非脱碘代谢途径，如结合 将通过分析代谢物来检查去缀合， 高效液相色谱法 使用纯化的近端肾小管细胞， 将研究肾甲状腺激素摄取，并将使用该系统 为了解决甲状腺激素摄取和稳态 分布可能受到细胞内 钙、pH和氧化还原电位。

The long term objective of this proposal is to study the mechanisms which regulate the peripheral tissue uptake and metabolism of thyroxine (T4), the main secretory product of the thyroid gland, and 3,5,3'- triiodothyronine, (T3), the most potent thyroid hormone as well as other iodothyronine metabolites. These studies will examine the role of renal production and tissue compartmentation of T3 and T4 with the circulation. Three general phenomena relating to thyroid hormone uptake will be examined in the proposed studies 1) vascular, 2) cell membrane 3) cellular or cytosolic. The perfused kidney system, established in this laboratory, provides the opportunity to study thyroid effect of other tissues. Using single-pass and recirculating kidney perfusion, the mechanisms regulating cellular thyroid hormone influx, and efflux will be explored. Free thyroid hormone fractions in cytosol and perfusate medium will be determined by equilibrium dialysis. The mechanisms underlying the extensive single-pass renal uptake of thyroid hormone will be sought and related to steady-state tissue thyroid hormone concentrations and metabolic rates. With this information, the dynamic uptake process will be mathematically modeled to aid the distinction between uptake by simple diffusion of free hormone and facilitated or active transport. Modeling of the translocation process is considerably simplified in this system as parameters such as hormone carrier protein type and concentration, ligand concentration, tissue transit time, and the significance of excretory and metabolic pathways can be controlled. These techniques will be employed to distinguish alterations in renal flux and steady-state distribution of iodothyronines in the presence of drugs competing with thyroid hormone binding to circulating or cellular proteins. Light microscopic autoradiography will be performed to identify the tissue and cellular loci of renal thyroid hormone exchange. A study will probe for differences in tissue/perfusate compartmentation of T3 generated by local 5'-deiodination of T4 compared to T3 derived from the circulation. THe effects of in vitro 5 '-deiodinase inhibitors, drugs competing with cellular hormone binding, and altered thyroid status will be examined. Nondeiodinative metabolic pathways such as conjugation and deconjugation will be examined by analysis of metabolites by high performance liquid chromatography. Using purified proximal tubular cells, the metabolic requirements of renal thyroid hormone uptake will be studies and this system will be used to address the hypothesis that thyroid hormone uptake and steady-state distribution may be acutely regulated by factors such as intracellular calcium, pH and redox potential.