Rat proximal NHE3 adapts to chronic acid-base disorders but not to chronic changes in dietary NaCl intake.
In the proximal tubule, the apical Na(+)/H(+) exchanger identified as NHE3 mediates most NaCl and NaHCO(3) absorption. The purpose of this study was to analyze the long-term regulation of NHE3 during alkalosis induced by dietary NaHCO(3) loading and changes in NaCl intake. Sprague-Dawley rats exposed to a low-NaCl, high-NaCl, or NaHCO(3) diet for 6 days were studied. Renal cortical apical membrane vesicles (AMV) were prepared from treated and normal rats. Na(+)/H(+) exchange was assayed as the initial rate of (22)Na(+) uptake in the presence of an outward H(+) gradient. (22)Na(+) uptake measured in the presence of high-dose 5-(N-ethyl-N-isopropyl) amiloride was not different among models. Changes in NaCl intake did not affect NHE3 activity, whereas NaHCO(3) loading inhibited (22)Na(+) uptake by 30%. AMV NHE3 protein abundance assessed by Western blot analysis was unaffected during changes in NaCl intake. During NaHCO(3) loading, NHE3 protein abundance was decreased by 65%. We conclude that proximal NHE3 adapts to chronic metabolic acid-base disorders but not to changes in dietary NaCl intake.
Eladari
Dominique
D
Institut National de la Santé et de la Recherche Médicale Unité 356, Institut Fédératif de Recherche 58, Université Pierre et Marie Curie, 75270 Paris Cedex 06, France.
Leviel
Françoise
F
Pezy
Françoise
F
Paillard
Michel
M
Chambrey
Régine
R
D000137:Acid-Base Imbalance / Q000378:metabolism*; D000222:Adaptation, Physiological; D000471:Alkalosis / Q000139:chemically induced / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007672:Kidney Cortex / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009318:Natriuresis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000008:administration & dosage; D017693:Sodium Bicarbonate / Q000008:administration & dosage; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D012979:Sodium Radioisotopes / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000032:analysis; D005723:gamma-Glutamyltransferase / Q000032:analysis
C000613387:Slc9a3 protein, rat; D017673:Sodium Chloride, Dietary; D012979:Sodium Radioisotopes; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D017693:Sodium Bicarbonate; D012964:Sodium; D005723:gamma-Glutamyltransferase; D000520:alpha-Glucosidases