title: Effects of various degrees of oxidative stress induced by intermittent hypoxia in rat myocardial tissues.
abstract: OBJECTIVE
  The aim of this study was to investigate the mechanism by which oxidative stress induced by chronic intermittent hypoxia (IH) causes myocardial damage in obstructive sleep apnoea syndrome.
  
  
  METHODS
  A total of 160 Wistar rats were divided into five experimental groups and subjected to chronic IH with different concentrations of oxygen (5%, 7.5%, 10% IH groups; 10% continuous oxygen and normoxia control groups). Eight rats from each group were sacrificed at the 2-, 4-, 6- and 8-week time points. Superoxide dismutase (SOD) activity, malondialdehyde (MDA) levels and total anti-oxidant capability (T-AOC) were measured in supernatants of heart homogenates. Expression of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, p22(phox) and NOX2, and thioredoxin-2 (Trx-2) genes were determined by measuring messenger RNA (mRNA) levels by real-time polymerase chain reaction.
  
  
  RESULTS
  Compared with the control groups, MDA levels increased over time in the IH groups, whereas T-AOC and SOD activity decreased over time. MDA, T-AOC and SOD activity peaked at 6 weeks into the IH treatment. The 5% IH group showed significantly higher expression of p22(phox) and thioredoxin-2 mRNA, as compared with the other IH groups, as well as the control groups.
  
  
  CONCLUSIONS
  The severity of oxidative stress induced by chronic IH in myocardial tissue was significantly correlated with the degree of IH. NADPH oxidase and Trx-2 are important mediators of oxidative stress induced by IH.
authors.affiliation: Respiratory Department, Tianjin Medical University General Hospital, Heping District, Tianjin, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.forename: Shuo
authors.initials: S
authors.lastname: Li
authors.forename: Nansheng
authors.initials: N
authors.lastname: Wan
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.forename: Run
authors.initials: R
authors.lastname: Guo
authors.forename: Baoyuan
authors.initials: B
authors.lastname: Chen
mesh_terms: D000818:Animals; D000860:Hypoxia / Q000150:complications*; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D023421:Models, Animal; D009206:Myocardium / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D020181:Sleep Apnea, Obstructive / Q000378:metabolism / Q000503:physiopathology; D013482:Superoxide Dismutase / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D008562:Membrane Glycoproteins; D008315:Malondialdehyde; D013879:Thioredoxins; D013482:Superoxide Dismutase; C500593:Cybb protein, rat; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C515768:Cyba protein, rat