ENDOCRINE CONTROL OF FETAL CARDIOVASCULAR DYNAMICS

拟议研究的目的是1)生成一个全面的 对心脏激素心钠素长期作用的认识 正常和应激状态下胎儿心血管功能的维持 条件，2)检查内分泌和旁分泌因素 调节正常和应激条件下ANF的释放，及其 在细胞和分子水平上的作用部位，以及3)探索 胎心房心钠素基因表达的发育规律及意义 以及应激在改变这一模式中的作用 表情。要研究的应激条件是长期低氧 和业务量扩张。所采取的方法是首先利用整体 建立动物模型以确定药物对心血管和肾脏的长期影响 ANF。其次，将使用全动物和细胞培养实验。 结合描述调节ANF释放的因素和 表情。第三，将使用分子技术来测定ANF 基因表达。这些研究将在以下时间在绵羊胚胎中进行 孕期依次为105~115天和130~140天(足月=145天) 以确定这些调控机制的发育变化。 要测量的心血管变量是动脉和静脉。 血压、心率、心输出量、血气和pH、红细胞压积和 血浆蛋白浓度、尿流率和尿排泄量 电解液。在第一系列实验中，长时间的- 长期输注ANF对胎儿心血管变量的影响将得到确定 在长期留置尿管的胎儿中。非国大参与返乡 动脉压、血容量和尿流量在延长期间恢复正常 低氧和容量负荷将通过使用特定的 ANF的拮抗剂。将进行第二系列实验 在长期留置尿管的胎儿中描绘出 内皮素、去甲肾上腺素和肾上腺素在调节心钠素释放中的作用 在培养的胎儿心房肌细胞中检测其直接作用 这些因素刺激心钠素的分泌和表达 信使核糖核酸。第三系列实验将在 胎儿心脏组织心钠素表达模式的测定 心房和心室中的信使RNA，以及延长时间的影响 缺氧或体积扩张改变这一表达。我们将测试 胎儿中的以下假设：1)ANF是一种重要的激素 心血管功能在正常状态下的长期维持 条件和在低氧或容量膨胀的应激期间，2) 内皮素和儿茶酚胺是心钠素释放的媒介，它们 直接作用于胎儿心房肌细胞，促进ANF分泌和 诱导ANF信使RNA的表达；3)ANF基因的水平 后者在胎儿心房和脑室的表达 一半的妊娠可由持续的低氧应激或容量引起。 扩张。这些研究很重要，因为它们将扩大我们的 宫内胎儿畸形的控制及应激知识 在出生的时候。

The purposes of the proposed studies are 1) to generate a comprehensive understanding of the role of the cardiac hormone ANF in the long-term maintenance of fetal cardiovascular function under normal and stress conditions, 2) to examine the endocrine and paracrine factors which regulate the release of ANF under normal and stress conditions, and their site of action at the cellular and molecular levels, and 3) to explore the developmental pattern of ANF gene expression in fetal atria and ventricles, and the effects of stress in altering this pattern of expression. The stress conditions to be studied are prolonged hypoxia and volume expansion. The approach taken is to first utilize the whole animal model to define the long-term cardiovascular and renal effects of ANF. Secondly, whole animal and cell culture experiments will be used in combination to delineate the factors which mediate ANF release and expression. Thirdly, molecular techniques will be used to determine ANF gene expression. These studies will be carried out in ovine fetuses at 105 to 115 days and 130 to 140 days gestation (term = 145 days) in order to determine the developmental changes in these regulatory mechanisms. The cardiovascular variables to be measured are arterial and venous pressures, heart rate, cardiac output, blood gases and pH, hematocrit and plasma protein concentration, urine flow rate and urinary excretion of electrolytes. In the first series of experiments, the effects of a long- term infusion of ANF on fetal cardiovascular variables will be determined in chronically catheterized fetuses. The involvement of ANF in returning arterial pressure, blood volume and urine flow to normal during prolonged hypoxia and volume loading will be investigated by the use of a specific antagonist for ANF. The second series of experiments will be carried out in chronically catheterized fetuses to delineate the effects of endothelin, norepinephrine and epinephrine in mediating ANF release, and in cultured fetal atrial cardiocytes to examine the direct effects of these factors in stimulating ANF secretion and expression of ANF messenger RNA. The third series of experiments will be carried out in fetal heart tissues to determine the pattern of expression of ANF messenger RNA in the atria and ventricles, and the effects of prolonged hypoxia or volume expansion in altering this expression. We will test the following hypotheses in the fetus: 1) ANF is an important hormone in the longterm maintenance of cardiovascular function under normal conditions and during the stress of hypoxia or volume expansion, 2) endothelin and the catecholamines are mediators for ANF release, and they act directly on fetal atrial cardiocytes to enhance ANF secretion and induce the expression of ANF messenger RNA, and 3) the level of ANF gene expression in the atria and ventricles of the fetus during the latter half of gestation can be induced by prolonged stress of hypoxia or volume expansion. These studies are important because they will expand our knowledge of the control of the fetal abnormalities in utero and stress at birth.