title: No adaptive response is induced by chronic low-dose radiation from Ra-226 in the CHSE/F fish embryonic cell line and the HaCaT human epithelial cell line.
abstract: OBJECTIVE
  To determine whether chronic low-dose α-particle radiation from Ra-226 over multiple cell generations can lead to an adaptive response in CHSE/F fish embryonic cells or HaCaT human epithelial cells receiving subsequent acute high-dose γ-ray radiation.
  
  
  METHODS
  CHSE/F and HaCaT cells were exposed to very low doses of Ra-226 in medium for multiple generations prior to being challenged by a higher dose γ-ray radiation. The clonogenic assay was used to test the clonogenic survival of cells with or without being pretreated by radiation from Ra-226.
  
  
  RESULTS
  In general, pretreatment with chronic radiation has no significant influence on the reaction of cells to the subsequent challenge radiation. Compared to unprimed cells, the change in clonogenic survival of primed cells after receiving challenge radiation is mainly due to the influence of the chronic exposure, and there's little adaptive response induced. However at several dose points, pretreatment of CHSE/F fish cells with chronic radiation resulted in a radiosensitive response to a challenge dose of γ-ray radiation, and pretreatment of HaCaT cells resulted in no effect except for a slightly radioresistant response to the challenge radiation which was not significant.
  
  
  CONCLUSIONS
  The results suggest that chronic low-dose radiation is not effective enough to induce adaptive response. There was a difference between human and fish cells and it may be important to consider results from multiple species before making conclusions about effects of chronic or low doses of radiation in the environment. The term "radiosensitive" or "adaptive" make no judgment about whether such responses are ultimately beneficial or harmful.
authors: Medical Physics & Applied Radiation Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L8, Canada. Electronic address: shix22@mcmaster.ca.
authors: Xiaopei
authors: X
authors: Shi
authors: Medical Physics & Applied Radiation Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L8, Canada.
authors: Carmel
authors: C
authors: Mothersill
authors: Medical Physics & Applied Radiation Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L8, Canada.
authors: Colin
authors: C
authors: Seymour
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002460:Cell Line; D002477:Cells / Q000528:radiation effects*; D006801:Humans; D010473:Perciformes; D011883:Radium
chemical_list: D011883:Radium
keywords: Adaptive effect; Chronic radiation; Clonogenic survival fraction; Ra-226; α-particle