Renal Transporters and Fetal Neuroendocrinology

描述(申请人提供)：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)轴活动的机制。提供对HPA轴活动的更完整的了解将是了解胎儿应激、动态平衡以及(在绵羊和其他物种中)控制分娩的关键。在过去的几年里，我们已经研究了几种控制绵羊胎儿HPA轴活动的生理和内分泌机制。我们已经报道，雌激素能有效地刺激胎儿HPA轴，雌二醇的主要循环形式是3-硫酸雌二醇，外源性3-硫酸雌二醇有效地刺激胎儿HPA轴活动。我们假设3-硫酸雌二醇可以通过一个或多个有机阴离子转运体(OAT‘s)被胎儿大脑直接摄取，OAT是已知的运输硫代偶联雌激素的转运体。我们还假设，在摄取和作用之前，雌二醇-3-硫酸盐可能是去结合的。拟议的实验旨在对这些假设进行机械性的检验。具体地说，我们提出了三个特定的目标：1)阐明有机阴离子转运体(OAT‘s)和类固醇硫酸酯酶(STS)在胎儿大脑吸收硫代结合雌激素中的作用；2)测试OAT在胎儿HPA轴中作为雌二醇-3-硫酸盐作用的介体；以及4)测试雌激素受体在HPA轴对雌二醇-3-硫酸盐反应中的生理作用。为了实现这些目标，我们将结合体内、药理学、生化和分子技术进行实验。综上所述，这些技术将使我们能够量化体内雌激素-3-硫酸盐的分泌和清除动力学以及大脑摄取，并使用OAT和STS活性的特定阻滞剂来测试这些转运和去调节系统在体内所起的作用。利用本实验室建立的生理、生化和分子技术，我们还将能够测试这些系统在HPA轴对3-硫酸雌二醇的反应中所起的作用。我们预计，这些研究的结果将导致设计药物策略来控制胎儿HPA在子宫内的活动。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，对控制胎儿应激激素的机制知之甚少，我们也缺乏安全有效的方法来控制胎儿应激激素的分泌。这一建议旨在提供对胎儿应激激素的新理解和操纵胎儿应激反应的新方法。

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.