Dawson Paul A
Department of Internal Medicine, Section on Gastroenterology, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, USA.
Handb Exp Pharmacol. 2011(201):169-203. doi: 10.1007/978-3-642-14541-4_4.
Membrane transporters expressed by the hepatocyte and enterocyte play critical roles in maintaining the enterohepatic circulation of bile acids, an effective recycling and conservation mechanism that largely restricts these potentially cytotoxic detergents to the intestinal and hepatobiliary compartments. In doing so, the hepatic and enterocyte transport systems ensure a continuous supply of bile acids to be used repeatedly during the digestion of multiple meals throughout the day. Absorption of bile acids from the intestinal lumen and export into the portal circulation is mediated by a series of transporters expressed on the enterocyte apical and basolateral membranes. The ileal apical sodium-dependent bile acid cotransporter (abbreviated ASBT; gene symbol, SLC10A2) is responsible for the initial uptake of bile acids across the enterocyte brush border membrane. The bile acids are then efficiently shuttled across the cell and exported across the basolateral membrane by the heteromeric Organic Solute Transporter, OSTα-OSTβ. This chapter briefly reviews the tissue expression, physiology, genetics, pathophysiology, and transport properties of the ASBT and OSTα-OSTβ. In addition, the chapter discusses the relationship between the intestinal bile acid transporters and drug metabolism, including development of ASBT inhibitors as novel hypocholesterolemic or hepatoprotective agents, prodrug targeting of the ASBT to increase oral bioavailability, and involvement of the intestinal bile acid transporters in drug absorption and drug-drug interactions.
肝细胞和肠细胞表达的膜转运蛋白在维持胆汁酸的肠肝循环中起着关键作用,这是一种有效的再循环和保存机制,在很大程度上限制了这些潜在的细胞毒性去污剂进入肠道和肝胆系统。通过这种方式,肝脏和肠细胞转运系统确保全天多餐消化过程中能持续供应可反复使用的胆汁酸。胆汁酸从肠腔的吸收以及进入门静脉循环是由肠细胞顶端和基底外侧膜上表达的一系列转运蛋白介导的。回肠顶端钠依赖性胆汁酸共转运蛋白(缩写为ASBT;基因符号,SLC10A2)负责胆汁酸跨肠细胞刷状缘膜的初始摄取。然后,胆汁酸通过异源有机溶质转运体OSTα-OSTβ有效地穿梭过细胞并从基底外侧膜输出。本章简要回顾了ASBT和OSTα-OSTβ的组织表达、生理学、遗传学、病理生理学和转运特性。此外,本章还讨论了肠道胆汁酸转运蛋白与药物代谢之间的关系,包括开发ASBT抑制剂作为新型降胆固醇或肝保护剂、将ASBT作为前药靶点以提高口服生物利用度,以及肠道胆汁酸转运蛋白在药物吸收和药物相互作用中的作用。