TRANSPORT IN SMALL PANCREATIC DUCTS

外分泌盐、水和消化酶的分泌 大多数囊性纤维化患者的胰腺严重受损 （CF）。 这种疾病是由囊性纤维化基因突变引起的。 跨膜传导调节因子（CFTR）蛋白，其作为一种 cAMP依赖性氯离子通道。 最近的免疫定位研究 证明CFTR的表达水平在人的乳腺癌中是高的， 排列在小胰管上的上皮细胞。 而反观 CFTR的表达水平在大胰管中较低， 在腺泡细胞中检测不到。 导管上皮细胞仅包括 占胰腺体积的5-10%，并埋在腺泡内 组织，因此难以进行研究。 因为这些 局限性，大多数关于导管细胞转运功能的结论是 基于转运抑制剂对体积的影响， 在体内或体外收集的分泌物的组合物， 整个胰腺 因此，我们对正常导管细胞的了解 运输功能贫乏，我们对胰腺的理解 CF的病理生理学是有限的。 本提案的总体目标是 是为了定量地了解 小胰管的运输特性，并确定 CFTR在导管碳酸氢钠分泌中的确切作用。 具体来说，我们将使用离体灌注的小叶内和小叶间 导管段，以确定基础和分泌素刺激率 液体分泌，分泌液体的离子组成，以及 导管上皮的跨上皮电特性。 常规和离子选择性细胞内微电极技术 可用于识别运输途径和确定 顶侧和底侧细胞的电化学驱动力 负责跨上皮转运的膜。 最后，程度 差异化的运输特性被导管保留 将测定在单层培养物中生长的上皮细胞。 的 从这些研究中获得的信息将用于批判性地 评估目前的胰腺导管分泌模型，更清楚地 定义CFTR在导管功能中的作用，并为 永生化导管上皮细胞系的评价。

The secretion of salt, water, and digestive enzymes by the exocrine pancreas is severely compromised in most patients with cystic fibrosis (CF). The disease results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein which functions as a cAMP-dependent chloride channel. Recent immunolocalization studies demonstrated that the level of expression of CFTR is high in the epithelial cells that line the small pancreatic ducts. In contrast, the level of expression of CFTR is low in large pancreatic ducts, and is undetectable in acinar cells. The ductal epithelial cells comprise only 5-10% of the volume of the pancreas and are buried within the acinar tissue, and thus poorly accessible for study. Because of these limitations, most conclusions about ductal cell transport function are based upon the effects of transport inhibitors on the volume and composition of secretions collected either in vivo or in vitro from the whole pancreas. Consequently, our knowledge of normal ductal cell transport function is meager, and our understanding of pancreatic pathophysiology in CF is limited. The overall objective of this proposal is to obtain a quantitative understanding of the transepithelial transport properties of small pancreatic ducts, and to determine the precise role of CFTR in ductal sodium bicarbonate secretion. Specifically, we will use isolated perfused intra- and inter-lobular ductal segments to determine the basal and secretin stimulated rates of fluid secretion, the ionic composition of the secreted fluid, and the transepithelial electrical properties of the ductal epithelium. Conventional and ion-selective intracellular microelectrode techniques win be used to identify transport pathways and to determine electrochemical driving forces at the apical and basolateral cell membranes responsible for transepithelial transport. Finally, the extent to which differentiated transport properties are retained by ductal epithelial cells grown in monolayer culture will be determined. The information obtained from these studies will be used to critically evaluate current models of pancreatic ductal secretion, more clearly define the role of CFTR in ductal function, and to provide a basis for evaluation of immortalized ductal epithelial cell lines.