Renal Transporters and Fetal Neuroendocrinology

描述（由申请方提供）：在本实验室进行的实验的总体目标是确定控制胎羊下丘脑-垂体-肾上腺（HPA）轴活性的机制。提供一个更完整的了解HPA轴的活动将是关键，了解胎儿的压力，稳态，和（在羊，也许在其他物种）分娩的控制。在过去的几年里，我们已经研究了几个生理和内分泌机制控制的活动，绵羊胎儿HPA轴。我们曾报道雌激素能有效地刺激胎儿HPA轴，雌二醇的主要循环形式是雌二醇-3-硫酸酯，外源性雌二醇-3-硫酸酯能有效地刺激胎儿HPA轴的活性。我们假设雌二醇-3-硫酸盐可以通过一种或多种有机阴离子转运蛋白（OAT）直接被胎脑吸收，这种转运蛋白已知可以转运磺基结合雌激素。我们还假设雌二醇-3-硫酸酯在吸收和作用之前可能是解结合的。所提出的实验旨在从机理上检验这些假设。具体而言，我们提出了三个具体的目标：1）阐明有机阴离子转运蛋白（OAT）和类固醇硫酸酯酶（STS）在胎脑摄取磺基结合雌激素中的作用; 2）测试OAT作为胎儿HPA轴中雌二醇-3-硫酸酯作用的介体;和4）测试雌激素受体在HPA轴对雌二醇-3-硫酸酯反应中的生理作用。为了实现这些目标，我们将使用体内，药理学，生物化学和分子技术的组合进行实验。总之，这些技术将使我们能够量化雌二醇-3-硫酸酯的分泌和清除动力学和脑摄取在体内，并使用特定的OAT和STS活性的阻断剂，以测试这些运输和去结合系统在体内发挥的作用。利用本实验室建立的生理、生化和分子技术，我们也将能够测试这些系统在HPA轴对雌二醇-3-硫酸酯反应中的作用。我们预计，这些研究的结果将导致在子宫内操纵胎儿HPA活动的药理学策略的设计。公共卫生相关性：胎儿应激是宫内胎儿死亡和发病的普遍原因。然而，对胎儿应激激素的调控机制知之甚少，缺乏安全有效的方法来调控胎儿应激激素的分泌。这项建议的目的是提供一个新的理解胎儿应激激素和新的方法来操纵胎儿应激反应。

DESCRIPTION (provided by applicant): The overall goal of the experiments performed in this laboratory are to identify the mechanisms controlling the activity of the hypothalamus-pituitary-adrenal (HPA) axis in fetal sheep. Providing a more complete understanding of the activity of the HPA axis will be key to understanding fetal stress, homeostasis, and (in sheep and perhaps in other species) the control of parturition. In past years, we have investigated several of the physiological and endocrine mechanisms controlling the activity of the ovine fetal HPA axis. We have reported that estrogen potently stimulates the fetal HPA axis, that the major circulating form of estradiol is estradiol-3-sulfate, and that exogenous estradiol-3-sulfate effectively stimulates fetal HPA axis activity. We have hypothesized that estradiol-3-sulfate could be taken up by the fetal brain directly through one or more organic anion transporters (OAT's), transporters that are known to transport sulfoconjugated estrogens. We have also hypothesized that the estradiol-3- sulfate might be deconjugated prior to both uptake and action. The proposed experiments are designed to test these hypotheses mechanistically. Specifically, we propose three specific aims: 1) to elucidate the roles of Organic Anion Transporters (OAT's) and steroid sulfatase (STS) in the uptake of sulfoconjugated estrogens by the fetal brain; 2) to test OAT's as mediators of estradiol-3-sulfate action in the fetal HPA axis; and 4) to test the physiological roles of estrogen receptors in HPA Axis responses to estradiol-3-sulfate. To achieve these aims, we will perform experiments using a combination of in vivo, pharmacological, biochemical, and molecular techniques. Together, these techniques will allow us to quantify estradiol-3-sulfate secretion and clearance kinetics and brain uptake in vivo, and use specific blockers of OAT and STS activity to test the roles played by these transport and deconjugation systems in vivo. Using physiological, biochemical, and molecular techniques well established in this laboratory, we will also be able to test the roles of these systems in the HPA axis response to estradiol-3-sulfate. We anticipate that the results of these studies will lead to the design of pharmacologic strategies for manipulating fetal HPA activity in utero. PUBLIC HEALTH RELEVANCE: Fetal stress is a prevalent cause of fetal death and morbidity in utero. Nevertheless, little is known about the mechanisms controlling the fetal stress hormones and we lack safe and effective ways of manipulating fetal stress hormone secretion. This proposal is aimed at providing a novel understanding of fetal stress hormones and novel approaches towards manipulating the fetal stress response.