Cortisol at MR Mediate Fetal Physiologic/Genomic Effects

描述（由申请方提供）：这些研究的总体目标是检验以下假设：在妊娠的大部分时间，胎儿中游离皮质醇的浓度通过高亲和力（皮质类固醇I型）盐皮质激素受体（MR）而不是低亲和力但高容量的糖皮质激素受体（GR）发挥生理作用。它是公认的高水平的皮质醇产生的胎儿肾上腺在交付时是重要的正常器官的成熟，这些影响是由GR介导的。MR的存在下，在胎儿组织早在妊娠中期表明，可能有低浓度的皮质醇通过MR的影响，甚至在胎儿成熟的时间。我们将测试皮质醇对MR受体的作用是否通过肺和/或肾中的特定MR靶基因介导对胎儿体积的影响，以及通过海马中的MR靶基因介导对下丘脑垂体-肾上腺功能的影响。组织中皮质类固醇的相对活性将与皮质类固醇的血浆水平、11 β-羟基类固醇脱氢酶和还原酶活性（11 β HSD）的活性、组织中MR和GR的水平以及改变基因表达的反式激活相关。将检测MR靶基因，包括早期反应基因Sgk和K-Ras，以及ENaC、Na/K ATP酶和5 HT 1A、MR和GR的更慢诱导基因。为了验证这一假设，我们设计了以下实验：1）定量测定孕晚期胎儿肾上腺成熟前后的肺、肾、心脏、海马、脑干和垂体等组织中MR和GR的蛋白质、mRNA和内源性类固醇的相对占有率，以及11 β HSD的活性（120- 140 d）; 2）测试阻断胎儿MR受体对成人中已知为MR介导的生理作用、肾功能和ACTH分泌的影响，以及对胎儿中可能的MR介导的功能、肺液体重吸收的影响; 3）测试MR占用率与这些生理作用之间的关系，以及对海马、肾和类似的胎肺中MR作用的所提出的靶基因的关系; 4）比较组合的MR和GR占用率对这些基因和生理作用的影响。

DESCRIPTION (provided by applicant): The overall goal of these studies is to test the hypothesis that for most of gestation, the concentrations of free cortisol in the fetus exert physiologic actions via the high affinity (corticosteroid type I) mineralocorticoid receptors (MR) rather than the lower affinity, but higher capacity, glucocorticoid receptors (GR). It is well established that the high levels of cortisol produced by the fetal adrenal at the time of delivery are important for normal organ maturation, and that these effects are mediated by GR. The presence of MR in fetal tissues as early as mid-gestation suggests that there may be effects of low concentrations of cortisol via MR, even before the time of fetal maturation. We will test whether cortisol action at MR receptors mediates effects on fetal volume through specific MR-target genes in the lung and/or kidney, and on hypothalamo pituitary-adrenal function via MR-target genes in the hippocampus. The relative activity of corticosteroids in the tissues will be related to plasma levels of corticosteroids, activity of 11beta-hydroxysteroid dehydrogenase and reductase activities (11betaHSD), levels of MR and GR in the tissue, and transactivation to alter gene expression. MR target genes, including the early response genes, Sgk and K-Ras, and more slowly induced genes for ENaC, Na/K ATPase and 5HT1A, MR and GR will be tested. To test this hypothesis, experiments were designed to: 1) Quantitate the protein, mRNA and relative occupancy by endogenous steroids of MR and GR, and activity of 11betaHSD in fetal tissues such as lung, kidney, heart, hippocampus, brainstem and pituitary in late gestation fetuses both before and after the time of fetal adrenal maturation (120-140d); 2) Test the effect of blockade of fetal MR receptors on physiologic actions known in the adult to be MR-mediated, renal function and ACTH secretion, and on a possible MR-mediated function in the fetus, lung liquid re-absorption; 3) Test for a relation between MR occupancy and these physiologic effects, and on the proposed target genes for MR action in hippocampus, kidney, and by analogy, fetal lung; 4) to compare the effect of combined MR and GR occupancy on these genes and physiologic actions.