title: Na-K-ATPase isoform (alpha 3, alpha 2, alpha 1) abundance in rat kidney estimated by competitive RT-PCR and ouabain binding.
abstract: For understanding the regulation of sodium reabsorption, it is important to know whether the alpha 2- or alpha 3-isoform of Na-K-adenosinetriphosphatase (Na-K-ATPase) is expressed in mammalian kidney in addition to the predominant alpha 1 beta 1-isozyme. Here we applied competitive polymerase chain reaction (PCR) for estimation of mRNA in parenchymal zones of rat kidney for comparison to high-affinity [3H]ouabain binding. The alpha 3-isoform mRNA was demonstrated to form 0.04-0.05% of the amount of alpha 1-isoform mRNA in the cortex, medulla, and papilla of rat kidney. The alpha 2-mRNA was demonstrated in all three zones and constituted 0.03% of the amount of alpha 1-mRNA in cortex. The abundance of the alpha 1 truncated mRNA was 0.1-0.8% of that of the alpha 1-mRNA. The upper limit for expression of Na-K-ATPase isozyme with high ouabain affinity (dissociation constant, 69-141 nM) was 0.096-0.14% of the concentration of alpha 1 beta 1-Na-K-ATPase. Thus a small but well-defined pool of alpha 2- and alpha 3-isoforms constitutes < or = 0.1% of the amount of alpha 1-isoform at both the mRNA and protein level in rat kidney.
authors.affiliation: Biomembrane Research Centre, August Krogh Institute, Copenhagen University, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Lücking
authors.forename: J M
authors.initials: JM
authors.lastname: Nielsen
authors.forename: P A
authors.initials: PA
authors.lastname: Pedersen
authors.forename: P L
authors.initials: PL
authors.lastname: Jørgensen
mesh_terms: D000818:Animals; D001483:Base Sequence; D007527:Isoenzymes / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D015335:Molecular Probes; D008969:Molecular Sequence Data; D010042:Ouabain / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D007527:Isoenzymes; D015335:Molecular Probes; D012333:RNA, Messenger; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase