title: Angiotensin II stimulation of Na(+)-H+ exchange in proximal tubule cells.
abstract: Experiments were performed to evaluate the effect of angiotensin II (ANG II) on the sodium transport activity of isolated intact rabbit proximal tubule cells. Initial rates of 22Na(+) uptake were measured in Na+-depleted and ouabain-treated cells in the presence of an opposing H+ gradient (pHin less than pHout). ANG II (10(-12)-10(-9) M) stimulated the initial rate of 22Na+ uptake by 33 +/- 2%, whereas amiloride (0.5 mM) inhibited both basal and ANG II-stimulated 22Na+ uptake. ANG II-stimulated rate of 22Na+ uptake was inhibited by the receptor antagonist saralasin. Additional experiments were performed to evaluate the effect of ANG II on the rate of recovery of pHin in acid-loaded proximal tubule cells. Cells were acid loaded by an NH4Cl pulse in the presence of the pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. ANG II increased the initial rate of intracellular alkalinization, and this effect was inhibited by amiloride (1.0 mM). ANG II stimulation increased the Vmax of H+ efflux (from 0.53 +/- 0.02 to 0.64 +/- 0.04 pH units/min) without changing the Km for extracellular Na+. The present findings indicate that physiological concentrations of ANG II stimulate an amiloride-sensitive Na+-H+ antiport in proximal tubule cells.
authors.affiliation: Department of Physiology and Biophysics, University of Alabama, Birmingham 35294.
authors.forename: G
authors.initials: G
authors.lastname: Saccomani
authors.forename: K D
authors.initials: KD
authors.lastname: Mitchell
authors.forename: L G
authors.initials: LG
authors.lastname: Navar
mesh_terms: D000468:Alkalies / Q000037:antagonists & inhibitors / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D012964:Sodium / Q000493:pharmacokinetics; D017923:Sodium-Hydrogen Exchangers
chemical_list: D000468:Alkalies; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000804:Angiotensin II; D000584:Amiloride; D012964:Sodium