REGULATORS OF CLARA CELL DIFFERENTIATION IN LUNG

在成年哺乳动物中，无纤毛的细支气管上皮(Clara) 细胞是细胞毒性和新陈代谢的主要场所 肺环境毒物需要通过 细胞色素P-450单加氧酶系统，无论这些化合物 通过吸入或摄入进入生物体。最近的一些 研究表明，母亲已经被 受到环境毒素的影响也可能因此处于危险之中 这些曝光量。胎儿呼吸道细胞的过程 分化为有功能的Clara细胞既是一个前奏，也是一个 产后现象。因为几乎没有任何信息 关于哪些因素调节Clara细胞的分化，也不是 关于生物活性的肺细胞毒素如何调节这一过程， 我们已经建议评估对Clara细胞的影响 一系列抑制或诱导的化合物的鉴别 细胞色素P-450系统。总体假设是，我们将成为 测试表明，改变肺细胞色素P的化合物- 成人体内450系统对Clara细胞的刺激作用 胎儿和新生动物的分化和成熟。 我们我们评估激素的影响，这些激素已经被证明 调节肺发育的其他方面(糖皮质激素和 黄体酮)，成人肝P-450的诱导剂(钠 苯巴比妥、阿罗氯、β-萘黄酮)，一种生物活性Clara 细胞特异性毒物(4-异丙醇类)和细胞色素抑制剂 P-450活性(SKF 525-A和氨基苯并三氮唑)。成就 分化的Clara细胞的成体细胞器组成 采用超微结构形态计量学方法进行评价。此外，这三家公司 将评估Clara细胞的主要功能：作用为 细支气管上皮细胞祖细胞，细胞色素P- 450介导的新陈代谢和细支气管壁的来源 蛋白质。~3H-胸腺嘧啶核苷参入率和细胞周转率 通过放射自显影和细支气管上皮细胞数量估计 将对密度进行定量评估。免疫细胞化学， 免疫化学、分光光度和酶活性分析 将被用来测量细胞色素P-450系统。 将使用免疫细胞化学和免疫化学方法 评估分泌功能的改变。这项提议提供了 这是一个独特的机会，可以评估 暴露在环境毒素中的新生儿和母亲的胎儿， 确定环境毒素对肺细胞类型的影响 这对一些正常的肺功能和 鉴定可能作为Clara细胞调节剂的化合物 差异化。

In adult mammals, the nonciliated bronchiolar epithelial (Clara) cell is the principal site for cytotoxicity and metabolism of pulmonary environmental toxicants which require activation via the cytochrome P-450 monooxygenase system, whether these compounds enter the organism via inhalation or ingestion. A number of recent studies suggest that the lungs of fetuses whose mothers have been subjected to environmental toxins also may be at risk as a result of these exposures. The process by which fetal airway cells differentiate into functional Clara cells is both a pre- and postnatal phenomenon. Because there is virtually no information on which factors regulate differentiation of the Clara cell, nor on how bioactivated pulmonary cytotoxins may modulate this process, we have proposed to evaluate the effects on Clara cell differentiation of a series of compounds which inhibit or induce the cytochrome P-450 system. The overall hypothesis we will be testing is that compounds which alter the pulmonary cytochrome P- 450 system in the adult function as stimulators of Clara cell differentiation and maturation in the fetal and neonatal animal. We we evaluate the effects of hormones which have been shown to regulate other aspects of lung development (glucocorticoids and progesterone), inducers of hepatic P-450s in adults (sodium phenobarbital, Arochlor, beta-naphthoflavone), a bioactivated Clara cell-specific toxicant (4-ipomeanol) and inhibitors of cytochrome P-450 activity (SKF 525-A and aminobenzotriazole). The attainment of adult organelle composition by differentiated Clara cells will be assessed by ultrastructural morphometry. In addition, all three major functions of the Clara cell will be assessed: role as progenitor of bronchiolar epithelial cells, site of cytochrome P- 450-mediated metabolism, and source of bronchiolar mucosecretory proteins. 3H-Thymidine incorporation and cell turnover will be estimated by autoradiography, and bronchiolar epithelial population densities will be assessed quantitatively. Immunocytochemical, immunochemical, spectrophotometric and enzymatic activity assays will be used to measure the cytochrome P-450 system. Immunocytochemical and immunochemical methods will be used to evaluate alterations in secretory function. This proposal offers a unique opportunity to assess the degree of hazard faced by neonates and fetuses of mothers exposed to environmental toxins, to define the impact of environmental toxins on a lung cell type which is pivotal for a number of normal lung functions and to identify compounds which may serve as regulators of Clara cell differentiation.