title: Comparison of clonogenic cell survival and DNA damage induced by188Re and X-rays in rat thyroid cells.
abstract: OBJECTIVE
  Ionizing radiation produces DNA lesions among which DNA double strand breaks (DSB) are the most critical events. Radiation of various energy types might differ in their biological effectiveness. Here, we compared cell survival and DNA damage induced by188Re and X-rays using γH2AX foci as a measure of DSB. The correlation between survival and residual foci was also analyzed.
  
  
  METHODS
  PCCl3 cells were irradiated with 200 kV X-rays (1.2 Gy/min) or 0.5-25 MBq/ml188Re (1 h irradiation) achieving doses up to 10 Gy. By blocking of sodium iodide symporter (NIS) essentially extracellular activity could be guaranteed. Survival fractions (SF) were detected by colony forming assay. Initial and residual γH2AX foci (15 min and 24 h after irradiation) were assessed by immunostaining. The relationship between SF and residual radiation induced γH2AX foci (RIF) was evaluated by Spearman and Pearson correlation tests.
  
  
  RESULTS
  We did not find significant differences between the survival curves in terms of the radiation quality. The D37values were 4.6 Gy and 4.2 Gy for188Re or X-ray, respectively. The initial foci numbers were in the same range for188Re and X-ray, but higher levels of residual foci persisted after X-rays in comparison to188Re (1 GyX-ray6.5 ± 0.2; 1 GyRe-1884.8 ± 0.2 RIF). Accordingly, for188Re a higher extent of DSB repair was found. The Spearman test revealed a significant (p < 0.01) correlation between SF and residual RIF for both radiation modalities.
  
  
  CONCLUSIONS
  No differences in terms of radiation were found for SF and initial foci. However, residual foci were lower for188Re than for X-rays. A prediction of SF by residual foci should consider the properties of the radiation qualities that influence foci removal and DSB repair.
authors: Dr. rer.medic. Roswitha Runge, Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum Carl Gustav Carus, Fetscherstr. 74, 01307 Dresden, Tel. +49 (0) 351 458 5481, Fax +49 (0) 351 458 5347, E-Mail: Roswitha.Runge@uniklinikum-dresden.de.
authors: Roswitha
authors: R
authors: Runge
authors: Jana
authors: J
authors: Arlt
authors: Liane
authors: L
authors: Oehme
authors: Robert
authors: R
authors: Freudenberg
authors: Jörg
authors: J
authors: Kotzerke
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000235:genetics / Q000528:radiation effects*; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004249:DNA Damage / Q000235:genetics*; D004307:Dose-Response Relationship, Radiation; D011829:Radiation Dosage; D011868:Radioisotopes / Q000009:adverse effects; D051381:Rats; D012211:Rhenium / Q000009:adverse effects*; D013961:Thyroid Gland / Q000473:pathology / Q000503:physiopathology* / Q000528:radiation effects*; D014965:X-Rays / Q000009:adverse effects*
chemical_list: D011868:Radioisotopes; D012211:Rhenium
keywords: 188Re; PCCl3 cells; X-ray; cell survival; correlation; γH2AX foci