CELL DIFFERENTIATION WITHIN THE LIVER ACINUS

其目的是阐明分子机制，通过它 成人肝腺泡的功能组织得到了实现。这是我们的 假设肝细胞的功能异质性是必要的 完成肝腺泡的最终功能，调节 肝末梢小静脉和胆汁中的溶质浓度。我们 提出基因表达的调控是通过 这是肝细胞功能异质性发展的结果。因此， 特别令人感兴趣的是：a.基因表达的变化 在从胎儿肝脏到成人肝脏的过渡过程中，以及B. 成体肝腺泡内的基因表达。苯巴比妥 (Pb)-诱导肝脏细胞色素P-450b和e(两种主要的BP诱导物) 表格)将被用作模型，因为在PB给药后，细胞色素 P-450蛋白和mRNAs主要在小鼠肝细胞中诱导表达。 腺泡的远侧半部(3区和2区)。具体来说，我们建议 回答这些问题：是否诱导细胞色素P-450b和e的mRNAs 发生在全部肝细胞还是部分肝细胞？其次，是异质的 铅对肝腺泡细胞色素P-450蛋白的诱导作用 主要在基因转录水平上被控制？第三， 这种肝细胞异质性的表现是什么时候确立的？它是 它是在胎儿生命中留下印记的，还是在出生后发展起来的，通过 分子机制？将使用原位杂交技术来 确定PB反应的肝细胞的带状定位 成人肝脏细胞色素P-450b和e基因的诱导。会的 也可以用来评估肝脏发育的时间 PB诱导的细胞色素P-450的异质性表达 基因被获得了。利用分离的细胞核进行体外转录检测 取自成年肝腺泡不同区域的肝细胞 评估转录速率的差异是否是主要机制 细胞色素P-450b和P-450b的异质性表达 PB后的E基因。通过探索涉及到的分子机制， 细胞色素P-450b和e基因表达的建立及调控 在肝腺泡内，这些实验应该提供对 肝脏达到成体所必需的调节步骤 肝腺泡的组织。

The objective is the elucidation of the molecular mechanisms by which the functional organization of the adult liver acinus is attained. It is our hypothesis that the functional heterogeneity of hepatocytes is necessary to accomplish the ultimate function of the liver acinus, the regulation of solute concentration in the terminal hepatic venule and in bile. We propose that regulation of gene expression is one of the mechanisms by which the functional heterogeneity of hepatocytes develops. Consequently, of particular interest are: a. the changes in gene expression occuring during the transition from fetal to adult liver, and b. the modulation of gene expression within the adult liver acinus. Phenobarbital (PB)-induction of liver cytochromes P-450 b and e (two major BP-inducible forms) will be used as a model since after PB administration, cytochrome P-450 proteins and mRNAs are induced predominantly in hepatocytes of the distal half of the acinus (zones 3 and 2). Specifically, we propose to answer these questions: Is induction of cytochromes P-450 b and e mRNAS occuring in all or in some hepatocytes? Secondly, is the heterogeneous PB-induction of cytochrome P-450 proteins within the liver acinus controlled predominantly at the level of gene transcription? And thirdly, when is this manifestation of hepatocyte heterogeneity established? It is imprinted in fetal life, or does it develop post-natally, and by which molecular mechanisms? In situ hybridization techniques will be used to determine the zonal localization of hepatocytes responding to PB with induction of cytochrome P-450 b and e mRNAs in the adult liver. It will also be used to assess the time of liver development at which the heterogeneous pattern of expression of the PB-inducible cytochrome P-450 genes is attained. In vitro transcription assays using nuclei isolated from hepatocytes of different zones of the adult liver acinus will be used to assess whether differences in transcription rate are the main mechanisms responsible for the heterogenous expression of the cytochromes P-450 b and e genes after PB. By probing the molecular mechanisms involved in the establishment and regulation of cytochrome P-450 b and e gene expression within the hepatic acinus, these experiments should provide insight into regulatory steps which are necessary for the liver to attain the adult organization of the liver acinus.