Hypoxia Effects on Amniotic Fluid Volume

描述(由申请人提供)：最近的研究表明，羊水(AF)的量是通过调节膜内吸收的速度来调节的，而血管内皮生长因子(VEGF)可能在这一调节中起着关键作用。这种吸收发生在流体静力、浓度和实验诱导的渗透梯度的情况下。然而，膜内转运的调节机制以及膜内吸收的调节机制尚不清楚。建议的研究利用长期置管的胎羊来表征膜内转运机制，并确定在常氧和三种形式的胎儿缺氧期间潜在的细胞和分子调节，这三种形式分别产生增加、不变或减少的房颤体积。我们将确定扩散和整体运输对膜内水和溶质吸收的贡献。这些解释将通过测量房颤中特定溶质到胎儿和胎儿到房颤方向的膜内单向通量来证实。通过研究血管内皮生长因子对体外培养的羊膜和羊膜细胞转运的影响，可以确定通过膜内途径调节被动转运和整体转运的细胞和分子机制。我们的总体假设是，膜内的整体血流是通过单向的小泡运输发生的；低氧增加了整体流动，但不是被动扩散；小泡运输的速度由羊膜中小泡的丰度和流动性决定。我们进一步假设，缺氧增加了血管内皮生长因子的表达，进而调节了小窝蛋白-1的表达和/或增加了囊泡的丰度和流动性。拟议的研究很重要，因为羊水过少是一种常见的临床问题，与胎儿缺氧有关，其中许多胎儿死于宫内，死亡原因是脐带压迫和新生儿死亡，死亡原因是呼吸窘迫。羊水过多与早产和包括缺氧性在内的胎儿疾病有关。拟议的研究将使我们对正常和低氧条件下的房颤容量调节的理解有很大的改善。这一认识将促进改进治疗房颤容量异常的治疗的合理基础，从而有助于降低胎儿和新生儿的发病率和死亡率。

DESCRIPTION (provided by applicant): Recent studies have shown that amniotic fluid (AF) volume is regulated by modulating the rate of intramembranous absorption and that vascular endothelial growth factor (VEGF) may play a pivotal role in this regulation. This absorption occurs against hydrostatic, concentration and experimentally induced osmotic gradients. However, the mechanisms mediating intramembranous transport as well as the regulation of intramembmnous absorption are unknown. The proposed studies utilize chronically catheterized fetal sheep to characterize intramembranous transport mechanisms and determine the underlying cellular and molecular regulation during normoxia and during 3 forms of fetal hypoxia which individually produce increased, unchanged, or reduced AF volume. We will determine the contribution of diffusion versus bulk transport to intramembranous absorption of water and solutes. These interpretations will be confirmed by measuring the intramembranous unidirectional fluxes of specific solutes in the AF to fetal and fetal to AF directions. The cellular and molecular mechanisms which regulate passive and bulk transfer through the intramembranous pathway will be determined by studying the effects of VEGF on transport in isolated amniotic membrane and amnion cells in culture. Our overall hypothesis is that intramembranous bulk flow occurs by unidirectional vesicular transport; that hypoxia augments bulk flow but not passive diffusion; and that the rate of vesicular transport is determined by the abundance and mobility of vesicles in the amnion. We further hypothesize that hypoxia augments VEGF expression which in turn regulates caveolin-1 expression and/or increases vesicle abundance and mobility. The proposed studies are important because oligohydramnios is a frequent clinical problem associated with fetal hypoxia accounting for many in utero fetal deaths due to cord compression and neonatal deaths due to respiratory distress. Polyhydramnios is associated with premature delivery and fetal diseases including anemic hypoxia. The proposed studies will lead to a dramatic improvement in our understanding of AF volume regulation under normal as well as hypoxic conditions. This knowledge will promote a rational basis for improved therapies to treat AF volume abnormalities, thereby helping to reduce fetal and neonatal morbidity and mortality.