title: Low-salt diet increases NO bioavailability and COX-2 vasoconstrictor prostanoid production in spontaneously hypertensive rats.
abstract: OBJECTIVE
  The ability of dietary sodium restriction to reduce the incidence of cardiovascular mortality and improve vascular function in hypertension still remains poorly understood. The aim of this study was to observe the effects of a long period of salt restriction on the vascular reactivity of mesenteric resistance arteries of SHRs.
  
  
  METHODS
  Male SHRs received either standard-salt diet (0.3% NaCl) or low-salt diet (0.03% NaCl) for 28weeks. Vascular reactivity was studied in mesenteric artery segments and the influence of cyclooxygenase-2 (COX-2), reactive oxygen species (ROS) and participation of the renin-angiotensin system were analyzed.
  
  
  RESULTS
  Decreased salt intake did not affect phenylephrine-induced vasoconstriction but increased acetylcholine-induced vasodilatation and also increased the response to phenylephrine after inhibition of NO synthase by L-NAME (100μM) and iNOS protein expression was elevated. Cyclooxygenase inhibitor indomethacin (10μM) and COX-2 inhibitor NS 398 (1μM) decreased the reactivity to phenylephrine in low-salt-treated group, and COX-2 protein expression was elevated in low-salt group. The effects of apocynin (10μM); superoxide anion scavenger, tiron (1mM); hydrogen peroxide scavenger, catalase (1000UmL(-1)); and ACE and AT1 receptor blockers, enalapril (10μM) and losartan (10μM) on vascular reactivity were not different between two groups. The levels of AT1 protein expression were similar in both groups.
  
  
  CONCLUSIONS
  Low-salt diet modulates mesenteric vascular responses via increased NO bioavailability suggested by increased iNOS protein expression and vasoconstrictor prostanoid production via COX-2 pathway, in SHRs. Neither ROS nor the local renin-angiotensin system is involved in these responses.
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: T C
authors.initials: TC
authors.lastname: Travaglia
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: R C M
authors.initials: RC
authors.lastname: Berger
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: M B
authors.initials: MB
authors.lastname: Luz
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: L B
authors.initials: LB
authors.lastname: Furieri
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: Junior R F
authors.initials: JR
authors.lastname: Ribeiro
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: D V
authors.initials: DV
authors.lastname: Vassallo
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: J G
authors.initials: JG
authors.lastname: Mill
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: I
authors.initials: I
authors.lastname: Stefanon
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil. Electronic address: paula.frizera@terra.com.br.
authors.forename: P F
authors.initials: PF
authors.lastname: Vassallo
mesh_terms: D000818:Animals; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D004039:Diet, Sodium-Restricted; D006973:Hypertension / Q000178:diet therapy* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008638:Mesenteric Arteries / Q000378:metabolism / Q000503:physiopathology; D009569:Nitric Oxide / Q000378:metabolism*; D011453:Prostaglandins / Q000378:metabolism*; D011918:Rats, Inbred SHR; D017382:Reactive Oxygen Species / Q000378:metabolism; D012084:Renin-Angiotensin System; D014661:Vasoconstriction
chemical_list: D011453:Prostaglandins; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D051546:Cyclooxygenase 2
keywords: COX-2; Endothelium; Hypertension; Low-salt diet; Reactive oxygen species; Vascular reactivity