title: [Bicarbonate reabsorption in proximal renal tubule: molecular mechanisms and metabolic acidosis].
abstract: HCO3(-) reabsorption in the renal tubules plays a critically important role in maintaining the global acid-base balance. Loss of HCO3(-) causes metabolic acidosis. Proximal renal tubule is the major site for HCO3(-) reabsorption, accounting for more than 80% of total HCO3(-) reabsorption along the nephron. Over the past more than half centuries, tremendous progresses have been made on understanding the molecular mechanisms underlying the HCO3(-) reabsorption in proximal tubules. The transepithelial movement of HCO3(-) involves the coordinated operation of machineries on both the apical and the basolateral membranes of the epithelial cells. On the apical domain, Na(+)-H(+) exchanger NHE3 and the vacuolar H(+)-ATPase are two major pathways mediating the apical uptake of HCO3(-)-related species. Taken together, NHE3 and H(+)-ATPase are responsible for about 80% of HCO3(-) reabsorption in the proximal tubule. The remaining 20% is likely mediated by pathways yet to be characterized. On the basolateral membrane, NBCe1 represents the only major known pathway mediating the extrusion of HCO3(-) coupled with Na(+) into the interstitial space. In the present article, we provide a historical view about the studies on the mechanisms of HCO3(-) reabsorption since 1940s. Moreover, we summarize the latest progresses emerging over the past decade in the physiological as well as pathological roles of acid-base transporters underlying the HCO3(-) reabsorption in proximal tubules.
authors.affiliation: Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science & Technology School of Life Science & Technology, Wuhan 430074, China. liming.chen@mail.hust.edu.cn.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Guo
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Chen
mesh_terms: D000138:Acidosis / Q000503:physiopathology*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000503:physiopathology*; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology; D025262:Vacuolar Proton-Translocating ATPases / Q000502:physiology
chemical_list: D001639:Bicarbonates; D017923:Sodium-Hydrogen Exchangers; D025262:Vacuolar Proton-Translocating ATPases