title: Differentiation of Na+-K+ pump in rat proximal tubule is modulated by Na+-H+ exchanger.
abstract: This study examines the effect of in vivo modulation of Na+-H+ exchange activity on the development of Na+-K+-ATPase in rat kidney proximal convoluted tubule (PCT) segments. To stimulate Na+-H+ exchanger (major entry pathway for Na in PCT), weanling rats were fed NH4Cl for 4 days to induce metabolic acidosis (MA). In vehicle (Vh)-fed rats PCT Na+-K+-ATPase activity (pmol Pi.mm tubule-1.h-1 +/- SE) increased from 481 +/- 78 at 16 days to 1,122 +/- 119 at 20 days. In 20-day-old chronic MA rats, PCT Na+-K+-ATPase activity was 1,717 +/- 109, i.e., significantly higher (P less than 0.01) relative to controls. Chronic MA had no effect on PCT Mg ATPase activity and on Na+-K+-ATPase in the medullary thick ascending limb (MTAL). To inhibit the Na+-H+ exchanger, weanling rats received amiloride (30 micrograms.100 g body wt-1.day-1) via osmotic minipump for 4 days. In Vh-treated rats PCT Na+-K+-ATPase increased from 481 +/- 78 at 16 days to 1,428 +/- 81 at 20 days. In rats given chronic amiloride, PCT Na+-K+-ATPase was significantly lower (858 +/- 75) at 20 days relative to controls but PCT Mg ATPase and MTAL Na+-K+-ATPase activity was the same as in controls. Chronic MA and amiloride had no significant effect on PCT Na+-K+-ATPase activity in adult rats. Acute MA and acute amiloride injection had no significant effect on PCT Na+-K+-ATPase in weanling rats.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, St. Göran's Children's Hospital, Karolinska Institute, Stockholm, Sweden.
authors.forename: Y
authors.initials: Y
authors.lastname: Fukuda
authors.forename: A
authors.initials: A
authors.lastname: Aperia
mesh_terms: D000138:Acidosis / Q000503:physiopathology; D000375:Aging; D000584:Amiloride / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D004247:DNA / Q000032:analysis; D066298:In Vitro Techniques; D007668:Kidney / Q000254:growth & development; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D008297:Male; D011506:Proteins / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D017923:Sodium-Hydrogen Exchangers; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D011506:Proteins; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D000584:Amiloride; D004247:DNA; D000254:Sodium-Potassium-Exchanging ATPase