response of Normal cells Following multiple radiation exposure under radiotherapy Setting

Radiotherapy is an established approach for killing of tumour cells. During the process, most of the normal cells also get affected due to direct exposure or by bystander effects. To measure the damage pattern in healthy cells, a pilot study was designed under radiotherapy settings. Right leg region of Strain ‘A’ male mice was locally exposed to Cobalt60 gamma radiation with a dose of 2 Gy/ day for 5 consecutive days. After completion of each fraction, blood haematology and γH2AX studies were performed at 1 h time point in blood and bone marrow cells. Chromosomal aberration study in bone marrow was carried out at 24 h post irradiation of each fraction for evaluation of DNA damage. γH2AX and chromosomal aberration were found significantly (p<0.001) increased with each consecutive dose upto 4th fractions. Blood hematology showed a linear reduction in total WBC counts which included the reduction in lymphocytes and increased granulocytes with each passing dose up to 4th fraction. However, non significant damage (p>0.05) for all parameters have been observed for 4th and 5th split doses. The study indicated that repeated exposure leads to damage fixation in normal cells, possibly indicating a state of adaptation.