REGULATION OF FETAL HEPATIC DEVELOPMENT

对出生后生活的适应涉及肝脏的生长和功能 差异化。这个子项目的基本假设是 正常和紊乱的肝细胞分化与 肝细胞增殖。这个项目之前的工作表明， 胎鼠肝细胞具有独立的增殖表型 通过旁分泌或自分泌有丝分裂原发出信号。此外，这一点 “有丝分裂原非依赖性”生长表现出一种复杂的个体发育模式 妊娠第17天和出生后第一周结束。多数 值得注意的是，扩散暂时停止了大约 分娩前后24小时。出生后第四天以后， 肝细胞逐渐达到其静止的成年状态。现在 提案的重点是细胞周期机制，它负责 这种模式。胎鼠肝细胞诱导培养体系的建立 已开发出体外静息超过96小时的方法。因此，我们建议 从细胞水平研究肝细胞增殖的调控 细胞周期依赖性蛋白激酶(CDK)，CDK阳性调节因子 (Cyclins)和CDK抑制剂(CKI)。这些成果将得到补充。 通过对CDK、Cyclin和CKI在体内的表达和调控的研究。一个 拟议研究的主要目标是确定细胞对细胞的 CKI对细胞周期的负调控与肝细胞的关系 差异化。后者将使用以下方法进行评估 肝脏葡萄糖所需两种酶的免疫细胞/组织化学 产生，葡萄糖-6-磷酸酶和PEPCK，以及其他肝细胞- 特定的标记。我们的观察将扩展到一个动物模型 胎儿发育受损，产妇在分娩前48小时内饥饿 老鼠中的术语。特别是，胰岛素在调节这些方面的作用 将研究IUGR胎儿培养的肝细胞的过程 为了阐明胎儿宫内生长的肝脏病理生理学 智力迟缓。

The adaptation to postnatal life involves liver growth and functional differentiation. The underlying hypothesis for this subproject is that normal and perturbed hepatocyte differentiation are co-regulated with hepatocyte proliferation. Previous work on this project has shown that fetal rat hepatocytes have a proliferative phenotype which is independent of signaling by paracrine or autocrine mitogens. Furthermore, this "mitogen-independent" growth shows a complex ontogenic pattern between the 17th day of gestation and the end of the first postnatal week. Most notably, there is a temporary cessation of proliferation for approximately 24 hr surrounding parturition. Beyond the fourth postnatal day, hepatocytes gradually attain their quiescent, adult state. The present proposal focuses on the cell cycle mechanisms which are responsible for this pattern. A culture system in which fetal rat hepatocytes are induced to quiesce in vitro over 96 hr has been developed. Thus, we propose to study regulation of hepatocyte proliferation in culture at the level of cell cycle-dependent protein kinases (CDKs), CDK positive regulators (Cyclins) and CDK inhibitors (CKIs). These results will be complemented by studies on CDK, Cyclin and CKI expression and regulation in vivo. A primary goal of the proposed studies is to determine the cell-to-cell relationship between negative cell cycle regulation by CKIs and hepatocyte differentiation. The latter will be assessed using immunocyto/histochemistry for two enzymes required for hepatic glucose production, glucose-6-phosphatase and PEPCK, as well as other hepatocyte- specific markers. Our observations will be extended to an animal model of impaired fetal growth, maternal starvation for 48 hr prior to delivery at term in the rat. In particular, the role of insulin in regulating these processes in cultured hepatocytes from IUGR fetuses will be investigated in order to elucidate the hepatic pathophysiology of intrauterine growth retardation.