title: Mechanisms of the elimination of low dose hyper-radiosensitivity in T-47D cells by low dose-rate priming.
abstract: OBJECTIVE
  To investigate the mechanisms of elimination of low-dose hyper-radiosensitivity (HRS) in T-47D cells induced by 0.3 Gy low dose-rate (LDR) priming.
  
  
  METHODS
  The mitotic ratio was measured using mitotic marker histone H3 phosphorylation in LDR primed as well as untreated T-47D cells. The HRS response in unprimed cells receiving medium which was irradiated after being harvested from unprimed cells was measured with or without serum present during cell conditioning. 4,6-benzylidene-D-glucose (BG) was used to inhibit protein synthesis during LDR priming.
  
  
  RESULTS
  LDR primed T-47D cells were HRS-deficient and showed a decrease in mitotic ratio with increasing dose while unprimed, i.e., HRS-competent T-47D cells, showed no decrease in mitotic ratio for doses in the HRS-range. HRS was eliminated in LDR primed cells, in cells receiving medium transfer from LDR primed cells, and in cells receiving LDR irradiated medium harvested from unprimed cells. The efficacy of the transferred medium depended on the presence of serum during cell conditioning. LDR priming eliminated HRS even in the presence of protein synthesis inhibitor BG.
  
  
  CONCLUSIONS
  LDR priming of T-47D cells as well as LDR priming of medium conditioned on T-47D cells induce a factor in the medium which cause the early G(2)-checkpoint to be activated in recipient cells by doses normally in the HRS dose-range.
authors.affiliation: Department of Physics, University of Oslo, Biophysics Group, PB 1048 Blindern, N-0316 Oslo, Norway. n.f.j.edin@fys.uio.no
authors.forename: Nina Jeppesen
authors.initials: NJ
authors.lastname: Edin
authors.forename: Dag Rune
authors.initials: DR
authors.lastname: Olsen
authors.forename: Trond
authors.initials: T
authors.lastname: Stokke
authors.forename: Joe Alexander
authors.initials: JA
authors.lastname: Sandvik
authors.forename: Peter
authors.initials: P
authors.lastname: Ebbesen
authors.forename: Erik Olai
authors.initials: EO
authors.lastname: Pettersen
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005947:Glucose / Q000031:analogs & derivatives / Q000494:pharmacology; D006657:Histones / Q000378:metabolism; D006801:Humans; D008938:Mitosis / Q000528:radiation effects; D010766:Phosphorylation; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology / Q000528:radiation effects*
chemical_list: D006657:Histones; C013844:benzylidene glucose; D005947:Glucose