Philp N J, Yoon H, Grollman E F
Pennsylvania College of Optometry, Philadelphia, Pennsylvania 19141-3399, USA.
Am J Physiol. 1998 Jun;274(6):R1824-8. doi: 10.1152/ajpregu.1998.274.6.R1824.
The retinal pigment epithelium (RPE) forms the outer blood-retinal barrier and regulates the movement of nutrients, water, and ions between the choroidal blood supply and the retina. The transport properties of the RPE maintain retinal adhesion and regulate the pH and osmolarity in the space surrounding the photoreceptor cell outer segments. In this report we identify two monocarboxylate transporters, MCT1 and MCT3, expressed in rat RPE. On the basis of Northern and Western blot analyses, MCT1 is expressed in both the neural retina and the RPE, whereas the expression of MCT3 is restricted to the RPE. Using indirect immunolocalization we show that the two transporters are polarized to distinct membrane domains. MCT1 antibody labels the apical surface and the apical processes of the RPE. A polyclonal antibody produced against the carboxy terminus of rat MCT3 labels only the basolateral membrane of the RPE. The demonstration of MCT1 on the apical membrane and MCT3 on the basal membrane identifies specific proteins involved in the discriminate and critical regulation of water and lactate transport from the retina to the choroid.
视网膜色素上皮（RPE）形成外血视网膜屏障，并调节脉络膜血液供应与视网膜之间营养物质、水和离子的移动。RPE的转运特性维持视网膜黏附，并调节光感受器细胞外段周围空间的pH值和渗透压。在本报告中，我们鉴定出在大鼠RPE中表达的两种单羧酸转运体，即MCT1和MCT3。基于Northern和Western印迹分析，MCT1在神经视网膜和RPE中均有表达，而MCT3的表达仅限于RPE。通过间接免疫定位，我们表明这两种转运体定位于不同的膜结构域。MCT1抗体标记RPE的顶端表面和顶端突起。针对大鼠MCT3羧基末端产生的多克隆抗体仅标记RPE的基底外侧膜。顶端膜上MCT1和基底膜上MCT3的证实，确定了参与从视网膜到脉络膜水分和乳酸转运的鉴别和关键调节的特定蛋白质。
