Quantitative RT-PCR analysis of mRNAs encoding a colonic putative H, K-ATPase alpha subunit along the rat nephron: effect of K+ depletion.
The rat nephron displays two ouabain-sensitive K-ATPases: one, which is present in proximal tubules and thick ascending limbs of normal rats, is specifically activated by K+ and is down-regulated by K+ depletion, whereas the other one appears in collecting ducts of K+-depleted rats and is activated by either Na+ or K+. To determine which of these two ATPases is similar to colonic-type H,K-ATPase, we quantitated by reverse transcriptase-polymerase chain reaction (RT-PCR) the mRNAs encoding the colonic H,K-ATPase alpha subunit in microdissected nephron segments. In normal rats, statistically significant amounts of colonic H,K-ATPase mRNAs were detected exclusively in cortical thick ascending limbs and cortical collecting ducts (200-500 copies/mm). Because these levels of expression were low (1-1.2 copies/target cell), they probably have no physiological relevance. In rats fed a K+-depleted diet for 2 weeks, expression of colonic H,K-ATPase was markedly enhanced in cortical and medullary collecting ducts (5000-12,000 copies/mm or 30-40 copies per cell), whereas it remained low in all other nephron segments. Thus, colonic H,K-ATPase alpha subunit is specifically expressed in cortical and outer medullary collecting ducts of K+-depleted rats where it likely accounts for the ouabain-sensitive K-ATPase activity.
Marsy
S
S
Laboratoire de Biologie Intégrée des Cellules Rénales, Service de Biologie Cellulaire, CEA Saclay, Unité 1859 associée au CNRS, France.
Elalouf
J M
JM
Doucet
A
A
D000818:Animals; D001483:Base Sequence; D003106:Colon / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017506:H(+)-K(+)-Exchanging ATPase / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D009399:Nephrons / Q000187:drug effects / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000502:physiology*; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D010042:Ouabain; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D017506:H(+)-K(+)-Exchanging ATPase; D011188:Potassium