title: Chronic antioxidant therapy lowers blood pressure in adult but not in young Dahl salt hypertensive rats: the role of sympathetic nervous system.
abstract: OBJECTIVE
  It is well-known that salt hypertension is associated with increased oxidative stress. Since the development of salt hypertension is age-dependent, we were interested whether young and adult salt hypertensive Dahl rats differ in oxidative stress level and/or in the effects of chronic antioxidant therapy on blood pressure (BP) level and on the participation of particular vasoconstrictor/vasodilator systems in BP maintenance.
  
  
  METHODS
  Young (5-week-old) and adult (12-week-old) salt-sensitive (Dahl-S) male rats were fed high-salt diet (5% NaCl) and drank tempol solution (2 mm) for 5 weeks. BP was monitored with radiotelemetry and vasoconstrictor/vasodilator balance was evaluated at the end of experiment. Moreover, NO synthase activity, superoxide production and lipoperoxidation were determined in heart, kidney and aorta in separate subgroups of Dahl rats.
  
  
  RESULTS
  Tempol treatment had quite opposite BP effects in young and adult Dahl-S rats. While it tended to increase BP in young salt hypertensive Dahl-S rats, it significantly lowered BP in the adult ones due to reduced sympathetic vasoconstriction. Importantly, high salt intake substantially reduced NO synthase activity in heart and kidney, and markedly increased superoxide production in kidneys and aorta of adult Dahl-S rats in which BP correlated positively with superoxide production in thoracic aorta and lipoperoxidation in kidneys.
  
  
  CONCLUSIONS
  Chronic antioxidant therapy lowered BP only in adult salt hypertensive Dahl-S rats in which superoxide levels were increased in both kidneys and aorta. Blood pressure reduction induced by chronic tempol treatment is related to attenuated sympathetic vasoconstriction rather than to augmented NO-dependent vasodilatation.
authors.affiliation: Institute of Physiology V.V.I, Academy of Sciences of the Czech Republic, Prague, Czech Republic. ivanava@biomed.cas.cz
authors.forename: I
authors.initials: I
authors.lastname: Vaněčková
authors.forename: M
authors.initials: M
authors.lastname: Vokurková
authors.forename: H
authors.initials: H
authors.lastname: Rauchová
authors.forename: Z
authors.initials: Z
authors.lastname: Dobešová
authors.forename: O
authors.initials: O
authors.lastname: Pecháňová
authors.forename: J
authors.initials: J
authors.lastname: Kuneš
authors.forename: J
authors.initials: J
authors.lastname: Vorlíček
authors.forename: J
authors.initials: J
authors.lastname: Zicha
mesh_terms: D000375:Aging; D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D003497:Cyclic N-Oxides / Q000008:administration & dosage / Q000494:pharmacology*; D006973:Hypertension / Q000188:drug therapy; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects; D051381:Rats; D020303:Rats, Inbred Dahl; D012965:Sodium Chloride / Q000009:adverse effects*; D013113:Spin Labels; D013564:Sympathetic Nervous System
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D013113:Spin Labels; D012965:Sodium Chloride; C001803:tempol
keywords: Dahl rats; age; reactive oxygen species; salt hypertension; tempol