Petrovic Snezana, Barone Sharon, Xu Jie, Conforti Laura, Ma Liyun, Kujala Minna, Kere Juha, Soleimani Manoocher
Division of Nephrology and Hypertension, Department of Medicine, University of Cincinnati, 231 Albert Sabin Way, MSB G259, Cincinnati, OH 45267-0585, USA.
Am J Physiol Renal Physiol. 2004 Jan;286(1):F161-9. doi: 10.1152/ajprenal.00219.2003. Epub 2003 Sep 9.
The outer medullary collecting duct (OMCD) plays an important role in bicarbonate reabsorption and acid-base regulation. An apical V-type H+-ATPase and a basolateral Cl-/HCO3- exchanger, located in intercalated cells of OMCD, mediate the bicarbonate reabsorption. Here we report the identification of a new basolateral Cl-/HCO3- exchanger in OMCD intercalated cells in rat kidney. Northern hybridizations demonstrated the predominant expression of this transporter, also known as SLC26A7, in the outer medulla, with lower expression levels in the inner medulla. SLC26A7 was recognized as a approximately 90-kDa band in the outer medulla by immunoblot analysis and was localized on the basolateral membrane of a subset of OMCD cells by immunocytochemical staining. No labeling was detected in the cortex. Double-immunofluorescence labeling with the aquaporin-2 and SLC26A7 antibodies or anion exchanger-1 and SLC26A7 antibodies identified the SLC26A7-expressing cells as alpha-intercalated cells. Functional studies in oocytes demonstrated that increasing the osmolality of the media (to simulate the physiological milieu in the medulla) increased the Cl-/HCO3- exchanger activity mediated via SLC26A7 by about threefold (P < 0.02 vs. normal condition). We propose that SLC26A7 is a basolateral Cl-/HCO3- exchanger in intercalated cells of the OMCD and may play an important role in bicarbonate reabsorption in medullary collecting duct.
外髓集合管（OMCD）在碳酸氢盐重吸收和酸碱调节中起重要作用。位于OMCD闰细胞中的顶端V型H⁺-ATP酶和基底外侧Cl⁻/HCO₃⁻交换体介导碳酸氢盐重吸收。在此，我们报告在大鼠肾脏OMCD闰细胞中鉴定出一种新的基底外侧Cl⁻/HCO₃⁻交换体。Northern杂交显示，这种也被称为SLC26A7的转运体在外髓中主要表达，在内髓中表达水平较低。通过免疫印迹分析，SLC26A7在外髓中被识别为一条约90 kDa的条带，通过免疫细胞化学染色定位在一部分OMCD细胞的基底外侧膜上。在皮质中未检测到标记。用 aquaporin-2和SLC26A7抗体或阴离子交换体-1和SLC26A7抗体进行双重免疫荧光标记，将表达SLC26A7的细胞鉴定为α闰细胞。卵母细胞功能研究表明，增加培养基渗透压（模拟髓质中的生理环境）可使通过SLC26A7介导的Cl⁻/HCO₃⁻交换体活性增加约三倍（与正常条件相比，P < 0.02）。我们提出，SLC26A7是OMCD闰细胞中的一种基底外侧Cl⁻/HCO₃⁻交换体，可能在髓质集合管的碳酸氢盐重吸收中起重要作用。
