Table_1_NBCe2 (Slc4a5) Is Expressed in the Renal Connecting Tubules and Cortical Collecting Ducts and Mediates Base Extrusion.DOCX

Arterial hypertension, is a common disorder with multiple and variable etiologies. Single nucleotide polymorphism analyses have detected an association between variants in the gene encoding the electrogenic Na+:HCO3– cotransporter NBCe2 (Slc4a5), and salt-sensitive hypertension. Mice with genetic deletion of NBCe2 are hypertensive, and the cause of the blood pressure (BP) increase is believed to arise from a lack of renal NBCe2 function. The exact cellular expression of NBCe2 in the kidney tubular system is, however, not determined. Here, we find NBCe2 to be expressed predominantly in isolated connecting tubules (CNT) and cortical collecting ducts (CD) by RT-PCR. In isolated renal CNT and CCD, genetic deletion of NBCe2 leads to decreased net base extrusion. To determine the role of renal NBCe2 in the development of hypertension, we generated CNT and intercalated cell NBCe2 knockout mice by crossing an Slc4a5 lox mouse with mice expressing cre recombinase under the V-ATPase B1 subunit promotor. Although the mice displayed changes in the expression of renal membrane transporters, we did not detect hypertension in these mice by tail cuff recordings. In conclusion, while global NBCe2 deletion certainly causes hypertension this study cannot confirm the role of renal NBCe2 expression in blood pressure regulation.

动脉高血压是一类病因多样且复杂的常见疾病。单核苷酸多态性分析已检测到编码生电性Na+:HCO3–协同转运蛋白NBCe2（Slc4a5）的基因变异与盐敏感性高血压存在关联。敲除NBCe2基因的小鼠会出现高血压表型，目前认为其血压（BP）升高的根源在于肾脏NBCe2功能缺失。然而，NBCe2在肾小管系统内的确切细胞表达定位尚未明确。本研究通过逆转录聚合酶链反应（RT-PCR）发现，NBCe2主要在分离的连接小管（CNT）和皮质集合管（CD，亦称CCD）中表达。在分离的肾脏连接小管与皮质集合管中，NBCe2基因敲除会导致碱基净外排水平下降。为明确肾脏NBCe2在高血压发生发展中的作用，我们将Slc4a5 lox小鼠与在V-ATP酶B1亚基启动子调控下表达Cre重组酶的小鼠杂交，构建了连接小管与闰细胞特异性NBCe2敲除小鼠。尽管此类小鼠的肾脏膜转运蛋白表达出现了改变，但通过尾袖套血压测量并未检测到高血压表型。综上，虽然全身NBCe2敲除确实会引发高血压，但本研究无法证实肾脏NBCe2表达在血压调控中发挥作用。