title: Human cell membrane oxidative damage induced by single and fractionated doses of ionizing radiation: a fluorescence spectroscopy study.
abstract: OBJECTIVE
  To investigate the production and repair of lipid oxidative damage in two human cell lines exposed to acute and fractionated dose of ionizing radiation. Radiation dose was in the range from 0.1 to 44 Gy.
  
  
  METHODS
  K562 and HL60 human cell lines have been used, 24 and 96 h after seeding. Membrane lipid oxidative damage has been detected by the measurement of the fluorescence decay of 1,6-diphenyl-1,3,5-hexatriene (DPH), its polarization value and the conjugated dienes concentration. The modification of DPH decay has been previously reported to be directly related to the lipid hydroperoxide concentration.
  
  
  RESULTS
  A modification of the DPH decay has been observed as a linear function of the logarithm of the radiation dose and only when the irradiation was performed in the presence of oxygen. The amount of the damage is related to the time after the cell medium change. By exposing the cells to fractionated radiation doses for several days (10 cGy day(-1)), the oxidative damage has been found to be cumulative. After a single acute dose, evidence of repair of the lipid oxidative damage was not obtained.
  
  
  CONCLUSIONS
  Following a previously developed method, the membrane damage was attributed to the production of hydroperoxide residues in the lipid acyl chains with the consequence of water penetration into the external portion of the bilayer, from the aqueous environment to the position of hydroperoxides. This damage is not repaired. The results obtained by measuring the DPH fluorescence decay have been compared with those obtained using other current optical and biochemical methods. None of these techniques could detect membrane oxidative damage at doses < 10 Gy. Finally, the different sensitivity of 'young' and 'old' cells to the oxidative damage can be related to different cholesterol concentrations.
authors.affiliation: Istituto di Medicina Sperimentale, CNR, Roma, Italy. tiziana@biocell.irmkant.rm.cnr.it
authors.forename: A M
authors.initials: AM
authors.lastname: Giusti
authors.forename: M
authors.initials: M
authors.lastname: Raimondi
authors.forename: G
authors.initials: G
authors.lastname: Ravagnan
authors.forename: O
authors.initials: O
authors.lastname: Sapora
authors.forename: T
authors.initials: T
authors.lastname: Parasassi
mesh_terms: D002462:Cell Membrane / Q000528:radiation effects; D004161:Diphenylhexatriene / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D005456:Fluorescent Dyes / Q000378:metabolism; D018922:HL-60 Cells / Q000528:radiation effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D020014:K562 Cells / Q000528:radiation effects; D015227:Lipid Peroxidation; D008563:Membrane Lipids / Q000378:metabolism / Q000528:radiation effects*; D010084:Oxidation-Reduction
chemical_list: D005456:Fluorescent Dyes; D008563:Membrane Lipids; D004161:Diphenylhexatriene; D006861:Hydrogen Peroxide