LUNG EPITHELIAL ION-LIQUID TRANSPORT DURING DEVELOPMENT

这个建议的目的是澄清如何离子输运性质 在发育过程中呼吸上皮的变化， 哺乳动物肺从出生前充满液体的Cl分泌器官到 一个充满空气吸收钠的器官 总的战略是 为了定义来源于以下的细胞中离子转运的发育变化： 呼吸道上皮的2个不同区域（气管，远端 肺），并将这些变化与 出生前后肺液体平衡的发育差异。 长期目标是提高对基本机制的认识 负责逆转液体流经肺上皮细胞， 出生，这应该提供有用的信息，制定有效的 抑制或促进婴儿肺水肿消退的措施， 儿童和成人。 具体目标集中在中心假设上， 与分娩和出生时的适应有关的事件，特别是 释放肾上腺激素（皮质醇、醛固酮和肾上腺素）， 影响上皮细胞代谢和Na-K-ATP酶活性， 由此产生的开关，从Cl-分泌钠吸收跨 支气管上皮 该项目使用4个互补 研究Na和Cl的机制和调节的实验方法 在发育中动物的呼吸道上皮中的运输：（1）气道 远端肺上皮细胞将从胎儿、新生儿和 2种成年动物，以测量放射性标记的 离子（86 Rb，36 Cl，22 Na），存在或不存在各种抑制剂 （2）生物电和离子传输特性 培养的气道和远端肺上皮细胞的汇合单层 将在细胞预先暴露于特定的 激素（糖皮质激素、醛固酮、β-肾上腺素能激动剂）， 妊娠后期浓度增加;（3）净产量 （分泌和吸收）管腔液体将在 胎儿和新生动物（兔， 绵羊）在基础和实验条件下（激素暴露， 用上皮离子转运的刺激剂和抑制剂治疗）; 和（4）净液体产量，离子浓度和跨上皮 将在胎羊的肺中测量电位差 在分娩前和分娩期间，有或没有事先暴露于激素， 在存在或不存在影响上皮细胞离子的各种药物的情况下， 运输 这些互补的实验方法允许（a） 在不同区域和在不同区域的离子输运性质的评估 发育中的呼吸道上皮的不同细胞;和（B） 阐明它们各自对液体分泌的贡献， 活体肺相关生理条件下的吸收 动物 这项工作可能有重要的影响，有关流体 新生儿肺部平衡和呼吸障碍 呼吸道上皮功能障碍

The purpose of this proposal is to clarify how ion transport properties of the respiratory epithelium change during development to convert the mammalian lung from a liquid-filled, Cl-secreting organ before birth to an air-filled, Na-absorbing organ after birth. The general strategy is to define developmental changes of ion transport in cells derived from 2 distinct regions of the respiratory tract epithelium (trachea, distal lung) of 2 species (rabbits, sheep), and to relate these changes to developmental differences in lung liquid balance before and after birth. The longterm objective is to improve understanding of basic mechanisms responsible for reversal of liquid flow across the lung epithelium near birth, which should provide useful information for developing effective measures to inhibit or promote resolution of pulmonary edema in infants, children and adults. Specific aims focus on the central hypothesis that events associated with labor and adaptation at birth, in particular the release of adrenal hormones (cortisol, aldosterone, and epinephrine), influence epithelial cell metabolism and Na-K-ATPase activity, with a resultant switch from Cl-secretion to Na-absorption across the bronchopulmonary epithelium. The project uses 4 complementary experimental approaches to study mechanisms and regulation of Na and Cl transport in the respiratory epithelium of developing animals: (1) airway and distal lung epithelial cells will be isolated from fetal, newborn and adult animals of 2 species in order to measure fluxes of radiolabeled ions (86Rb,36Cl, 22Na) in the presence or absence of various inhibitors of ion transport; (2) bioelectric and ion transport properties of confluent monolayers of cultured airway and distal lung epithelial cells will be assessed with and without prior exposure of the cells to specific hormones (glucocorticoids, aldosterone, beta-adrenergic agonists) that increase in concentration late in gestation; (3) net production (secretion and absorption) of luminal liquid will be measured in isolated, blood-perfused lungs of fetal and newborn animals (rabbits, sheep) under basal and experimental conditions (hormone exposure, treatment with stimulants and inhibitors of epithelial ion transport); and (4) net liquid production, ion concentrations and transepithelial electrical potential difference will be measured in lungs of fetal sheep before and during labor, with and without prior exposure to hormones, and in the presence or absence of various drugs that influence epithelial ion transport. These complementary experimental approaches permit (a) assessment of ion transport properties at different regions and in different cells of the developing respiratory epithelium; and (b) clarification of their respective contributions to liquid secretion and absorption under relevant physiological conditions in lungs of living animals. This work may have important implications concerning fluid balance in the newborn lung and breathing disorders associated with respiratory epithelial dysfunction.