title: Role of angiotensin II and oxidative stress on renal aquaporins expression in hypernatremic rats.
abstract: The aim of this study was to assess whether endogenous Ang II and oxidative stress produced by acute hypertonic sodium overload may regulate the expression of aquaporin-1 (AQP-1) and aquaporin-2 (AQP-2) in the kidney. Groups of anesthetized male Sprague-Dawley rats were infused with isotonic saline solution (control) or with hypertonic saline solution (Na group, 1 M NaCl), either alone or with losartan (10 mg kg(-1)) or tempol (0.5 mg min(-1) kg(-1)) during 2 h. Renal function parameters were measured. Groups of unanesthetized animals were injected intraperitoneally with hypertonic saline solution, with or without free access to water intake, Na+W, and Na-W, respectively. The expression of AQP-1, AQP-2, Ang II, eNOS, and NF-kB were evaluated in the kidney by Western blot and immunohistochemistry. AQP-2 distribution was assessed by immunofluorescence. Na group showed increased natriuresis and diuresis, and Ang II and NF-kB expression, but decreased eNOS expression. Losartan or tempol enhanced further the diuresis, and AQP-2 and eNOS expression, as well as decreased Ang II and NF-kB expression. Confocal immunofluorescence imaging revealed labeling of AQP-2 in the apical plasma membrane with less labeling in the intracellular vesicles than the apical membrane in kidney medullary collecting duct principal cells both in C and Na groups. Importantly, our data also show that losartan and tempol induces a predominantly accumulation of AQP-2 in intracellular vesicles. In unanesthetized rats, Na+W group presented increased diuresis, natriuresis, and AQP-2 expression (112 ± 25 vs 64 ± 16; *p < 0.05). Water deprivation increased plasma sodium and diuresis but decreased AQP-2 (46 ± 22 vs 112 ± 25; §p < 0.05) and eNOS expression in the kidney. This study is a novel demonstration that renal endogenous Ang II-oxidative stress, induced in vivo in hypernatremic rats by an acute sodium overload, regulates AQP-2 expression.
authors.affiliation: Department of Pathophysiology, University of Buenos Aires, INFIBIOC-CONICET, Buenos Aires, Argentina, sdellapenna@ffyb.uba.ar.
authors.forename: Silvana L
authors.initials: SL
authors.lastname: Della Penna
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cao
authors.forename: Nicolás M
authors.initials: NM
authors.lastname: Kouyoumdzian
authors.forename: Lorena
authors.initials: L
authors.lastname: Sarati
authors.forename: Andrea
authors.initials: A
authors.lastname: Fellet
authors.forename: Ana M
authors.initials: AM
authors.lastname: Balaszczuk
authors.forename: Marcelo R
authors.initials: MR
authors.lastname: Choi
authors.forename: Elsa
authors.initials: E
authors.lastname: Zotta
authors.forename: Susana
authors.initials: S
authors.lastname: Gorzalczany
authors.forename: Marcela
authors.initials: M
authors.lastname: Pandolfo
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Toblli
authors.forename: María I
authors.initials: MI
authors.lastname: Rosón
authors.forename: Belisario E
authors.initials: BE
authors.lastname: Fernández
mesh_terms: D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D020346:Aquaporins / Q000378:metabolism*; D015153:Blotting, Western; D005455:Fluorescent Antibody Technique; D006955:Hypernatremia / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D018384:Oxidative Stress; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D020346:Aquaporins; D000804:Angiotensin II