title: Localization of NBC1 variants in rat kidney.
abstract: Na+-HCO3- cotransporter (NBC1) plays a major role in bicarbonate reabsorption from proximal tubules. In a previous immunohistochemical study on human kidney, we showed that the kidney-type transporter (kNBC1) was abundantly expressed in the basolateral membranes of proximal tubules while the expression of pancreatic-type transporter (pNBC1) was undetectable. In the present study we tried to determine the localization of NBC1 variants in rat kidney using the antibodies against the unique N-terminal regions of kNBC1 and pNBC1. In Western blot analysis on the membrane-enriched fraction from rat kidney both anti-kNBC1 and anti-pNBC1 antibodies yielded a approximately 130 kDa band. In immunohistochemical analysis with confocal microscopy the anti-kNBC1 antibody produced a strong and exclusively basolateral labeling in proximal tubules. On the other hand, the occasional pNBC1 labeling was detected in the apical membranes of proximal tubules. The electron microscopic observation further supported the basolateral localization of kNBC1 as well as the localization of pNBC1 on the basis of the brush border. Acute metabolic acidosis did not change the protein expression levels as well as the intracellular distribution of both NBC1 variants in rat kidney. These results are consistent with a view that kNBC1 is the dominant variant that mediates bicarbonate reabsorption from rat renal proximal tubules. They also indicate that species difference may exist regarding the distribution of NBC1 variants in kidney.
authors.affiliation: Department of Internal Medicine, Faculty of Medicine, Tokyo University, Tokyo, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Endo
authors.forename: Satoru
authors.initials: S
authors.lastname: Yamazaki
authors.forename: Nobuo
authors.initials: N
authors.lastname: Moriyama
authors.forename: Yuehong
authors.initials: Y
authors.lastname: Li
authors.forename: Takashi
authors.initials: T
authors.lastname: Ariizumi
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kudo
authors.forename: Hayato
authors.initials: H
authors.lastname: Kawakami
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Shoko
authors.initials: S
authors.lastname: Horita
authors.forename: Hideomi
authors.initials: H
authors.lastname: Yamada
authors.forename: George
authors.initials: G
authors.lastname: Seki
authors.forename: Toshiro
authors.initials: T
authors.lastname: Fujita
mesh_terms: D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D006801:Humans; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D027982:Sodium-Bicarbonate Symporters / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: C422004:Slc4a4 protein, rat; D027982:Sodium-Bicarbonate Symporters