title: [Myocardial free radical metabolic changes in rats after repeated high +Gz exposure and protective effects of low-G preconditioning and tea polyphenols].
abstract: OBJECTIVE
  To determine whether repetitive exposure to high sustained +Gz acceleration induces persisting changes in the myocardial free radical metabolism and observe the protective effects of low-G training and antioxidant tea polyphenols (TP).
  
  
  METHODS
  Thirty-two male Wistar rats were randomly divided into four groups (n=8 each): group A, restrained, was only submitted to +1 Gz for 5 min. Group B, centrifuged, was exposed to five plateaus of 30 s at +10 Gz for intermittent times, three times a week, for three weeks. Group C, low-G trained, was exposed to +2 Gz for 5 min about 1 h prior to +10 Gz stress, and group D was orally given TP at dose of 200 mg/kg about 1 h prior to +10 Gz stress. On the next day morning after last centrifuge run, the rats were decapitated and the hearts were quickly removed. Malondialdehyde (MDA) concentration and superoxide dismutase (SOD) activity were measured. Additionally, CuZn-SOD and inducible NO synthase (iNOS) enzymatic contents were examined by immunohistochemical staining and their mRNA were analyzed by semi-quantitative reverse transcription polymerase chain reaction(RT-PCR).
  
  
  RESULTS
  Compared with group A, MDA concentration and iNOS enzymatic content in myocardial mitochondria were increased significantly (P < 0.05) in group B. Compared with group B, mitochondrial SOD activity was significantly increased in group C (P < 0.05). iNOS enzymatic content was significantly decreased in group C and D. There were no significant differences of CuZn-SOD content, CuZn-SOD and iNOS mRNA levels among the four groups.
  
  
  CONCLUSIONS
  Repeated high +Gz exposure can induce myocardial free radical metabolic disorder and mainly result in mitochondrial peroxidative injury. But low-G training and natural antioxidant TP have protective effects, and the former is better.
authors.affiliation: Institute of Aviation Medicine, Beijing 100036, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhan
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jiang-yang
authors.initials: JY
authors.lastname: Lu
authors.forename: Qing-jun
authors.initials: QJ
authors.lastname: Zhang
authors.forename: Yi-mei
authors.initials: YM
authors.lastname: Xin
authors.forename: Tong
authors.initials: T
authors.lastname: Li
authors.forename: Si-huang
authors.initials: SH
authors.lastname: Wei
mesh_terms: D000054:Acceleration; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D005609:Free Radicals / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D059808:Polyphenols / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013662:Tea / Q000737:chemistry
chemical_list: D005609:Free Radicals; D059808:Polyphenols; D013662:Tea