title: Effect of multiple freeze-thaw cycles of cytoplasm samples on the activity of antioxidant enzymes.
abstract: BACKGROUND
  In this paper the activity of cytoplasmatic antioxidant enzymes after multiple freeze-thaw cycles of samples of cytoplasm was assayed in order to characterise the limits that would be necessary to impose on experimental design.
  
  
  METHODS
  The activities of antioxidant enzymes in samples of rat liver cytoplasm were evaluated after 1, 2, 3, 4, 5, 10 and 15 freeze-thaw cycles. The activity of antioxidant enzymes was determined by standard methods developed for this purpose.
  
  
  RESULTS
  The most resistant against freeze-thaw stress was catalase; even 15 freeze-thaw cycles did not change its activity. The remaining enzymes tested revealed a significant loss in their activity after 4-5 freeze-thaw cycles. The most sensitive was glutathione S-tranferase; its activity was significantly decreased after 3 thaw cycles.
  
  
  CONCLUSIONS
  The data presented may be helpful in designing experiments in which assay of antioxidant enzymes is a part.
authors.affiliation: Department of Toxicology, Poznan University of Medical Sciences, Dojazd 30, 60-631 Poznan, Poland. amm@am.poznan.pl
authors.forename: Marek
authors.initials: M
authors.lastname: Murias
authors.forename: Magdalena
authors.initials: M
authors.lastname: Rachtan
authors.forename: Jadwiga
authors.initials: J
authors.lastname: Jodynis-Liebert
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D019411:Clinical Laboratory Techniques / Q000379:methods*; D003593:Cytoplasm / Q000201:enzymology*; D004795:Enzyme Stability; D005615:Freezing; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000201:enzymology; D008297:Male; D010088:Oxidoreductases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013696:Temperature
chemical_list: D000975:Antioxidants; D010088:Oxidoreductases; C121849:superoxide reductase; D002374:Catalase; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase