title: Paradoxical dose- and time-dependent regulation of superoxide dismutase and antioxidant capacity by vitamin E in rat.
abstract: BACKGROUND
  Previous data about the regulation of SOD activity as the key part of the endogenous antioxidant system by vitamin E is conflicting.
  
  
  METHODS
  We investigated the effect of different nontoxic doses of vitamin E on erythrocyte SOD activity and plasma total antioxidant capacity in rats, receiving 0 (control group), 100, 300 and 600 mg vitamin E/kilogram of body weight intramuscularly twice a week over 6-weeks.
  
  
  RESULTS
  We observed a linear increase in SOD activity in the first dosing group, which was significant (p<0.05) after 6th week compared to the control level. There was an increase in SOD activity at the end of 2nd and significant increase after 4th weeks, which was followed by a significant decrease at the end of 6th week in the second dosing group. In the third dosing group, there was a significant increase at the end of 2nd week and a significant decrease at the end of 4th and 6th weeks in the SOD activity. The changes in plasma antioxidant capacity were parallel to that of SOD activity with a significant and strong degree of correlation in the 4th and 6th weeks (r=0.7 and r=0.8, respectively). Serum levels of Vitamin E also increased in a time- and dose-dependent manner; the highest level was achieved in the 600 mg/kg dosing group after 6 weeks.
  
  
  CONCLUSIONS
  Non-toxic doses of vitamin E at some levels can up-regulate SOD activity, but cumulative effect of the same doses can lead to attenuation of SOD activity and hence antioxidant defense.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Tehran University of Medical Sciences, Tehran 14155, Iran.
authors.forename: Abolfazl
authors.initials: A
authors.lastname: Golestani
authors.forename: Roghieh
authors.initials: R
authors.lastname: Rastegar
authors.forename: Ahmad
authors.initials: A
authors.lastname: Shariftabrizi
authors.forename: Shahnaz
authors.initials: S
authors.lastname: Khaghani
authors.forename: Seyed Mehdi
authors.initials: SM
authors.lastname: Payabvash
authors.forename: Amirali H
authors.initials: AH
authors.lastname: Salmasi
authors.forename: Ahmad R
authors.initials: AR
authors.lastname: Dehpour
authors.forename: Parvin
authors.initials: P
authors.lastname: Pasalar
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000097:blood*; D014810:Vitamin E / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D014810:Vitamin E; D013482:Superoxide Dismutase