ROLE OF H+/HCO3- TRANSPORT IN BILE FORMATION

胆汁的形成是一个重要的，但知之甚少。 肝功能 胆汁的形成始于 小管以及申请人和其他人最近的研究表明 小管胆汁的形成部分是由于 肝细胞转运HCO 3-。 导管和小管也是 据信通过分泌HCO 3来促进胆汁的形成-- 丰富的流体，但很少有人知道有关的机制或 调节小管分泌，主要是因为缺乏一个 合适的实验模型。 该提案概述了各项研究， 基于主要研究者最近的观察结果， 一般涉及溶质和水运动的机制， 肝脏，特别关注H+和HCO 3-转运的作用 在肝细胞和导管细胞形成胆汁中的作用。 申请人 提出（a）进一步表征肝Na+/HCO 3-共转运， 一种以前未被认识到的肝脏HCO 3转运机制 他和他的同事们最近在肝细胞中发现了这种蛋白（B）， 检验高胆汁酸作用的假设，部分是通过 刺激肝细胞的H+和HCO 3-转运 还参与调节细胞内pH的机制 (pHi)（c）确定细胞内pH和 胆汁酸的葡萄糖醛酸化，（d）开发一个系统来建立 原代培养物中的胆管上皮细胞，和（e）定义 小管细胞中存在的H+和HCO 3-转运机制 并确定对这些运输机制的影响， 据信可增强胆管分泌的利胆剂。 这些研究将采用既定的方法和模式， 申请人最近开发的技术（例如荧光 测量培养的肝细胞中的pHi），以及模型 和技术（例如，肝导管细胞的原代培养物， 单个肝细胞或导管细胞中的pHi测量） 目前正在开发中。

The formation of bile is an important yet poorly understood hepatic function. Bile formation begins at the level of the canaliculus and recent studies by the applicant and others suggest that formation of canalicular bile results, in part, from active transport of HCO3- by hepatocytes. Ducts and ductules are also believed to contribute to bile formation via secretion of a HCO3-- rich fluid, yet little is known regarding the mechanism(s) or regulation of ductular secretion, largely because of the lack of an appropriate experimental model. This proposal outlines studies, base on recent observations by the Principal Investigator, which relate generally to mechanisms of solute and water movement by liver and focus specifically on the roles of H+ and HCO3-transport in bile formation by hepatocytes and ductular cells. The applicant proposes to (a) further characterize hepatic Na+/HCO3- symport, a previously unrecognized mechanism of hepatic HCO3- transport which he and his colleagues recently identified in hepatocytes, (b) test the hypothesis that hypercholeretic bile acids act, in part, by stimulating H+ and HCO3- transport by hepatocytes via mechanisms also involved in the regulation of intracellular pH (pHi), (c) define the relationship between intracellular pH and glucuronidation of bile acids, (d) develop a system for establishing bile ductular epithelial cells in primary culture, and (e) define the mechanism(s) of H+ and HCO3- transport present in ductular cells and determine the effects on these transport mechanism of choleretic agents believed to enhance ductular secretion. The studies will employ established methods and models and techniques recently developed by the applicant (e.g. fluorescence measurement of pHi in cultured hepatocytes), as well as models and techniques (e.g., primary cultures of hepatic ductular cells, measurement of pHi in individual hepatocytes or ductular cells) currently under development.