Hypoxia Effects on Amniotic Fluid Volume

描述（由申请人提供）：最近的研究表明，羊水（AF）的体积是通过调节膜内吸收率来调节的，血管内皮生长因子（VEGF）可能在这一调节中起关键作用。这种吸收发生在流体静力、浓度和实验诱导的渗透梯度上。然而，介导膜内转运以及调节膜内吸收的机制尚不清楚。拟议的研究利用长期插管的胎羊来表征膜内运输机制，并确定在正常缺氧和三种形式的胎儿缺氧期间潜在的细胞和分子调控，这三种形式的胎儿缺氧分别导致心房颤动量增加、不变或减少。我们将确定扩散与散装运输对膜内水和溶质吸收的贡献。这些解释将通过测量特定溶质在心房到胎儿和胎儿到心房方向的膜内单向通量来证实。通过研究VEGF在离体羊膜和培养羊膜细胞中对运输的影响，将确定通过膜内途径调节被动和大量转运的细胞和分子机制。我们的总体假设是膜内大流量通过单向囊泡运输发生；缺氧增加了大流量，但没有增加被动扩散；囊泡运输的速率是由羊膜中囊泡的丰度和流动性决定的。我们进一步假设缺氧会增加VEGF的表达，进而调节caveolin-1的表达和/或增加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，导致许多子宫内胎儿因脐带压迫而死亡，新生儿因呼吸窘迫而死亡。羊水过多与早产和包括贫血性缺氧在内的胎儿疾病有关。所提出的研究将大大提高我们对正常和缺氧条件下心房颤动体积调节的理解。这一知识将为改进房颤容量异常的治疗方法提供合理的基础，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.