Rajendran V M, Binder H J
Department of Internal Medicine, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06520, USA.
Ann N Y Acad Sci. 2000;915:15-29. doi: 10.1111/j.1749-6632.2000.tb05220.x.
This study describes the identification and characterization of anion transporters in apical membrane (APM) and basolateral membrane (BLM) of rat distal colon. Cl-HCO3, Cl-OH, Cl-butyrate, and butyrate-HCO3 exchanges and Na-HCO3 cotransporter are present in rat distal epithelial cells. Cl-HCO3 exchange (1) is present only in APM from surface, but not from crypt cells; (2) is also present in BLM; and (3) of surface cell is encoded by anion exchange (AE)-1 isoform, whereas BLM Cl-HCO3 is encoded by AE2 isoform. Cl-OH exchange is present only in APM, but not in BLM from surface and crypt cells, and is responsible for regulation of cell functions (i.e., cell pH and cell volume regulation). Butyrate-HCO3 exchange (1) is also present in apical membrane vesicles (AMV) from surface, but not from crypt cells; (2) is present in BLM; and (3) is responsible for SCFA-dependent HCO3 secretion. By contrast, Cl-butyrate exchange: (1) is present in APM from both surface and crypt cells; (2) is not present in BLM; and (3) recycles butyrate by absorbing Cl. Na-HCO3 cotransport: (1) is present only in BLM; (2) is expressed predominantly in midcrypt regions; and (3) may be linked to HCO3 secretion. A mechanism for HCO3 movement across the crypt apical membrane has not as yet been identified.
本研究描述了大鼠远端结肠顶端膜（APM）和基底外侧膜（BLM）中阴离子转运体的鉴定与特征。大鼠远端上皮细胞中存在Cl-HCO3、Cl-OH、Cl-丁酸盐和丁酸盐-HCO3交换以及Na-HCO3共转运体。Cl-HCO3交换：（1）仅存在于表面细胞的APM中，隐窝细胞中不存在；（2）也存在于BLM中；（3）表面细胞的Cl-HCO3交换由阴离子交换（AE）-1亚型编码，而BLM中的Cl-HCO3交换由AE2亚型编码。Cl-OH交换仅存在于APM中，表面细胞和隐窝细胞的BLM中不存在，负责调节细胞功能（即细胞pH和细胞体积调节）。丁酸盐-HCO3交换：（1）也存在于表面细胞的顶端膜囊泡（AMV）中，隐窝细胞中不存在；（2）存在于BLM中；（3）负责短链脂肪酸依赖性HCO3分泌。相比之下，Cl-丁酸盐交换：（1）存在于表面细胞和隐窝细胞的APM中；（2）BLM中不存在；（3）通过吸收Cl回收丁酸盐。Na-HCO3共转运：（1）仅存在于BLM中；（2）主要在隐窝中部区域表达；（3）可能与HCO3分泌有关。目前尚未确定HCO3跨隐窝顶端膜移动的机制。
