title: Role of mitochondrial DNA in radiation exposure.
abstract: OBJECTIVE
  To evaluate the role of mitochondrial DNA (mtDNA) following exposure to ionizing irradiation.
  
  
  METHODS
  We examined two human osteosarcoma cell lines either lacking mtDNA (143B.rho(0)206; rho0 cells) or having normal mtDNA (143B.TK-; rho+ cells). Cell survival curves were generated by using colony formation and micronucleus assay. The delay in population doubling time after irradiation was evaluated with dye exclusion tests.
  
  
  RESULTS
  No significant difference was seen between rho+ and rho0 cell lines in colony formation assay. In micronucleus assay, rho0 cells showed a significantly lower rate of micronucleus formation. The ratios of binucleated cells with micronuclei were 0.49 for rho+ cells and 0.25 for rho0 cells (p=0.005). In the dye exclusion test, rho0 cells revealed a delay of about 1.6 times in population doubling time compared with the control after 5 Gy of irradiation, similar to the 1.7 times of rho+ cells.
  
  
  CONCLUSIONS
  In the human osteosarcoma cell line 143B.TK-, mtDNA does not influence clonogenic survival and delay of population doubling time after irradiation. However, the difference in micronucleus formation shows that mtDNA influences DNA damage after radiation exposure.
authors.affiliation: Division of Multidisciplinary Radiotherapy, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yoshida
authors.forename: H
authors.initials: H
authors.lastname: Yamazaki
authors.forename: S
authors.initials: S
authors.lastname: Ozeki
authors.forename: T
authors.initials: T
authors.lastname: Inoue
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshioka
authors.forename: T
authors.initials: T
authors.lastname: Inoue
mesh_terms: D002455:Cell Division / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage / Q000528:radiation effects; D004272:DNA, Mitochondrial / Q000502:physiology*; D006801:Humans; D015162:Micronucleus Tests; D012516:Osteosarcoma / Q000473:pathology / Q000532:radiotherapy; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000235:genetics*; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D014410:Tumor Stem Cell Assay
chemical_list: D004272:DNA, Mitochondrial