CELL DIFFERENTIATION WITHIN THE LIVER ACINUS

其目的是阐明的分子机制， 获得成年肝腺泡的功能性组织。 是我们 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， 终末肝微静脉和胆汁中的溶质浓度。 我们 提出基因表达的调节是 肝细胞的功能异质性发展。 因此，委员会认为， 特别感兴趣的是：a.基因表达的变化 在从胎儿到成人肝脏的转变期间，和B.的调制 基因在成年肝腺泡内的表达。 苯巴比妥 （PB）-诱导肝细胞色素P-450 B和e（两种主要的BP-诱导 形式）将用作模型，因为PB给药后，细胞色素 P-450蛋白和mRNA主要在肝细胞中诱导， 腺泡的远侧半部分（3区和2区）。 具体来说，我们建议 回答这些问题：诱导细胞色素P-450 B和E是mRNAS吗 发生在所有或部分肝细胞中？ 其次，是异质性 PB诱导肝腺泡内细胞色素P-450蛋白 主要控制在基因转录水平上？ 第三， 这种肝细胞异质性的表现是什么时候确立的？ 是 是在胎儿时期形成的，还是在出生后形成的， 分子机制？ 原位杂交技术将用于 确定响应PB的肝细胞的区域定位， 诱导成人肝脏中的细胞色素P-450 B和e mRNA。 它将 也可用于评估肝脏发育的时间， PB诱导的细胞色素P-450表达的异质性模式 基因已经实现。 使用分离的细胞核的体外转录测定 将使用来自成体肝腺泡不同区域的肝细胞 以评估转录速率的差异是否是 负责细胞色素P-450 B和 e基因在PB之后。 通过探索参与的分子机制， 细胞色素P-450 B和E基因表达调控 在肝腺泡内，这些实验应该提供对 调节步骤是必要的肝脏达到成人 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.