title: In situ localization of anion exchanger-2 in the human kidney.
abstract: Na+-independent anion exchangers (AE) are a family of membrane carriers that mediate the electroneutral exchange of Cl- for HCO3- ions across plasma membranes. They are involved in intracellular pH and cell volume regulation as well as in transepithelial acid-base transport. While anion exchanger-1 (AE1) has been localized previously in the human kidney, thus far there has been no definite report on anion exchanger-2 (AE2) in this human tissue. Accordingly, immunohistochemistry was carried out on surgical specimens of the human kidney (fixed in formalin and embedded in paraffin), using a specific AE2 monoclonal antibody. Strong immunostaining was observed at the basolateral membrane of cells of thick ascending limbs and distal convoluted tubules, colocalizing with the basal membranous labyrinth of cellular interdigitations, typical of these segments. In fact, AE2 staining was attenuated at the macula densa, where basal infoldings are scarce. Additionally, in situ hybridization experiments on formalin-fixed tissue demonstrated the presence of AE2 mRNA in the same segments of the distal nephron. On the other hand, control immunohistochemistry with a monoclonal antibody against AE1 gave the expected immunoreactivity at the basal pole of the type A intercalated cells of connecting tubules and cortical collecting ducts, and in erythrocytes. Our results indicate that, depending on the nephron segment and corresponding cell types, AE1 and AE2 proteins are differentially involved in the Na+-independent exchange of Cl- for HCO3- at the basolateral membrane of polarized kidney epithelial cells.
authors.affiliation: Department of Internal Medicine, Clínica Universitaria and Medical School, University of Navarra, Pamplona, Spain.
authors.forename: J E
authors.initials: JE
authors.lastname: Castillo
authors.forename: E
authors.initials: E
authors.lastname: Martínez-Ansó
authors.forename: R
authors.initials: R
authors.lastname: Malumbres
authors.forename: E
authors.initials: E
authors.lastname: De Alava
authors.forename: C
authors.initials: C
authors.lastname: García
authors.forename: J F
authors.initials: JF
authors.lastname: Medina
authors.forename: J
authors.initials: J
authors.lastname: Prieto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D027321:Anion Transport Proteins; D000911:Antibodies, Monoclonal / Q000276:immunology; D017920:Antiporters; D001639:Bicarbonates / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D007424:Intracellular Fluid / Q000737:chemistry; D017136:Ion Transport; D007668:Kidney / Q000737:chemistry*; D007680:Kidney Neoplasms / Q000737:chemistry / Q000648:ultrastructure; D008297:Male; D008565:Membrane Proteins / Q000032:analysis*; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000032:analysis / Q000276:immunology; D009399:Nephrons / Q000737:chemistry / Q000648:ultrastructure; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D064606:SLC4A Proteins; D012964:Sodium / Q000502:physiology
chemical_list: D027321:Anion Transport Proteins; D000911:Antibodies, Monoclonal; D017920:Antiporters; D001639:Bicarbonates; D002712:Chlorides; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D064606:SLC4A Proteins; D012964:Sodium