title: Peroxynitrite and the regulation of Na(+),K(+)-ATPase activity by angiotensin II in the rat proximal tubule.
abstract: NO reacts spontaneously with superoxide to produce the potent oxidant peroxynitrite. Studies were designed to examine the role of NO-derived oxidants and peroxynitrite on the regulation of Na(+),K(+)-ATPase activity by angiotensin II (ANG II) freshly isolated rat proximal tubules. At picomolar concentrations ANG II stimulates Na(+),K(+)-ATPase activity, but at nanomolar concentrations stimulation is lost. Superoxide dismutase (SOD) was used to examine the role of superoxide and deferoxamine (DFO) and uric acid (UA) were used to examine the role of peroxynitrite. SOD (200 U/mL, 5-min preincubation) restored the stimulatory effect of ANG II (1.31 +/- 0.08-fold; n = 4; P < 0.05 compared to 10(-7) M alone), suggesting a role for superoxide. DFO (100 microm, 5-min preincubation) also restored the stimulatory effect of ANG II (1.40 +/- 0.08-fold; n = 4; P < 0.05, compared to 10(-7) M alone), as did UA (1.22 +/- 0.07-fold; n = 5; P < 0.05, compared to 10(-7) M alone). The NO synthesis inhibitor, N-monomethyl-L-arginine (L-NMMA, 2 mM; 5-min preincubation), also unmasked a stimulatory effect of ANG II at 10(-7) M (1.4 +/- 0.1-fold; n = 7; P < 0.05, compared to 10(-7) M alone). The generation of peroxynitrite was further evidenced by the formation of 3-nitrotyrosine (3-NT). 3-NT increased 3.5-fold in tubules exposed to ANG II (10(-7) M) (0.0054 +/- 0.0019 3-NT/100 tyrosines for control and 0.019 +/- 0.0058 3-NT/100 tyrosines for ANG II, P < .05; n = 4) and L-NMMA prevented the increase. These data suggest that peroxynitrite signaling participates in the regulation of renal of Na(+),K(+)-ATPase activity.
authors.affiliation: Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Mail Slot 611, 4301 W. Markham Street, Little Rock, AR 72205, USA.
authors.forename: Chaojie
authors.initials: C
authors.lastname: Zhang
authors.forename: Syed Z
authors.initials: SZ
authors.lastname: Imam
authors.forename: Syed F
authors.initials: SF
authors.lastname: Ali
authors.forename: Philip R
authors.initials: PR
authors.lastname: Mayeux
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D009566:Nitrates / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D026361:Reactive Nitrogen Species / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D014527:Uric Acid / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D009566:Nitrates; D026361:Reactive Nitrogen Species; D000804:Angiotensin II; C039642:peroxynitric acid; D014527:Uric Acid; D019323:omega-N-Methylarginine; D013482:Superoxide Dismutase; D000254:Sodium-Potassium-Exchanging ATPase; D003676:Deferoxamine