MECHANISMS OF THYROID HORMONE ACTION IN DEVELOPMENT

这项研究计划的长期目标是阐明 甲状腺激素（TH）的作用在分子水平上通过一项研究 激素代谢、激素受体 两栖动物物种发育中的相互作用和激素作用：蛙 catesbeiana和墨西哥钝口螈Ambystoma mexicanum。 由于各种原因，包括 TH受体存在于它们的细胞核中， 甲状腺素（T_4）转化为3，5，3 ′-三碘甲状腺原氨酸（T_3）能力 在变态之前，这些动物提供了独特的机会 来调查这些关系。 研究1-5都关注 具有负责在肝脏中从T4产生T3的酶系统（I5'Ds） 及其在TH作用中的调节和意义。 这些系统将被 通过测定它们的动力学性质在体外表征，并且 发育、TH、禁食和动物维持温度的影响 将被研究。 活性将与血浆中的T3和T4水平相关 和肝细胞质以及肝受体占有率。 肝脏也会 检测T4 5-单脱碘酶活性。 研究6将确定是否 尾部组织中的受体数量增加，就像红细胞中一样， 在自发和TH诱导的变态过程中。 研究7关注 对蛋白质具有相对较低亲和力的tetrac 受体，在蝌蚪中LT 3的效力相当。 研究8将 研究催乳素抑制和肾上腺皮质激素分泌的机制， 皮质激素增强蝌蚪TH的某些作用。 可能机制 包括对TH代谢和分布的影响，以及受体数量和 亲和力 研究9-12关注T3对 转录和翻译前事件，以及 TH作用中的假定受体。 可翻译的mRNA水平 氨甲酰磷酸合成酶（CPS）存在于肝脏中的自发和 诱导的变态将被确定并与CPS活性相关， 血浆和肝胞液中的T3和T4水平以及受体占有率。 一 CPSmRNA的cDNA探针将用于确定T3是否增加了 的CPSmRNA。 T3类似物刺激CPSmRNA的相对效力 将活性与它们对受体的相对亲和力进行比较。 最后，研究了变态和TH对整个mRNA活性的影响， 剖面，通过聚丙烯酰胺凝胶上的二维分离测定 肝多聚（A+）RNA的体外翻译产物。

The long-term goal of this research program is to elucidate the mechanisms of action of thyroid hormones (TH) at the molecular level through a study of the relationships between hormone metabolism, hormone-receptor interactions and hormone action in developing amphibian species: Rana catesbeiana and Ambystoma mexicanum. For a variety of reasons, including the facts that TH receptors are present in their nuclei and they acquire the ability to convert thyroxine (T4) to 3,5,3'triiodothyronine (T3) in vivo just prior to metamorphosis, these animals offer a unique opportunity to investigate these relationships. Studies 1-5 are all concerned with with enzyme systems responsible for producing T3 from T4 (I5'Ds) in liver and their regulation and significance in TH action. The systems will be characterized in vitro by determining their kinetic properties, and the effects of development, TH, fasting and animal maintenance temperatures will be studied. Activity will be related to T3 and T4 levels in plasma and liver cytosol, and hepatic receptor occupancy. Liver will also be examined for T4 5-monodeiodinase activity. Study 6 will determine whether receptor number in tail tissue is increased, as it is in erythrocytes, during spontaneous and TH-induced metamorphosis. Study 7 is concerned with the reason why tetrac, which has a relatively low affinity for the receptor, is comparable in potency in LT3 in tadpoles. Study 8 will investigate the mechanisms by which prolactin inhibits, and adrenal corticoids augment some actions of TH in tadpoles. Possible mechanisms include effects on TH metabolism and distribution, and receptor number and affinity. Studies 9-12 are concerned with the actions of T3 on transcription and pretranslational events, and the relevance of the putative receptors in TH action. The levels of translatable mRNA for carbamyl phosphate synthetase (CPS) present in liver during spontaneous and induced metamorphosis will be determined and correlated with CPS activity, T3 and T4 levels in plasma and liver cytosol, and receptor occupancy. A cDNA probe for CPSmRNA will be used to determine if T3 increases the amount of CPSmRNA. The relative potencies of T3 analogues in stimulating CPSmRNA activity will be compared with their relative affinities for the receptor. Lastly, the effects of metamorphosis and TH on the entire mRNA activity profile, as determined by 2-dimensional separation on polyacrylamide gels of in vitro translated products of hepatic poly(A+)RNA, will be determined.