Renal Transporters and Fetal Neuroendocrinology

描述（由申请人提供）：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）轴活动的机制。更全面地了解下丘脑轴的活动将是理解胎儿应激、体内平衡和（在绵羊和其他物种中）分娩控制的关键。在过去的几年里，我们研究了几种控制绵羊胎儿HPA轴活性的生理和内分泌机制。我们报道了雌激素能有效刺激胎儿HPA轴，雌二醇的主要循环形式是雌二醇-3-硫酸盐，外源性雌二醇-3-硫酸盐能有效刺激胎儿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体（OAT）直接被胎儿大脑吸收，这些转运体已知可以运输硫代结合的雌激素。我们还假设雌二醇-3-硫酸酯可能在摄取和作用之前被解结。所提出的实验旨在从机制上检验这些假设。具体来说，我们提出了三个具体目标：1)阐明有机阴离子转运体（OAT）和类固醇硫酸酯酶（STS）在胎儿大脑对硫代结合雌激素的摄取中的作用；2)检测OAT作为雌二醇-3-硫酸酯在胎儿下丘脑轴中作用的介质；4)检测雌激素受体在HPA轴对雌二醇-3-硫酸反应中的生理作用。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。总之，这些技术将使我们能够量化体内雌二醇-3-硫酸盐的分泌、清除动力学和脑摄取，并使用OAT和STS活性的特异性阻滞剂来测试这些转运和脱偶联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，我们也将能够测试这些系统在HPA轴对雌二醇-3-硫酸反应中的作用。我们预计这些研究的结果将导致在子宫内操纵胎儿HPA活性的药理学策略的设计。

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.