Effects of low-dose irradiation on chromosomal damage and oxidative stress in cultured human peripheral blood

Aim: To investigate the effects of low doses of X-ray exposure on chromosomal damage and antioxidants level in cultured human peripheral blood. Methodology: Blood samples collected from healthy young volunteers (male and female) in sterile heparinized tubes were irradiated at 97 kVp with 300 mAs using X-rays machine. In-vitro irradiation of whole blood was performed at different doses (0, 25, 50, 100, 200 and 300 mGy) with an average dose rate of 19.6 mGysec(-1). After irradiation, the lymphocytes were collected and cultured for 72 hr. Micronuclei (MN) assay was carried out following the standard protocol for the assessment of chromosomal damage. The level of glutathione (GSH), activities of glutathione-s-transferase (GST) and superoxide dismutase (SOD) were estimated from the blood plasma. Malondialdehyde (MDA) content was also estimated to determine oxidative stress after low-dose irradiation. Results: A significant positive correlation (r(2)=0.98, p<0.001) was observed between total MN frequency and irradiation dose in human peripheral blood lymphocytes. Irradiation of blood also caused significant decrease in GSH level and GST activities with increased in irradiation dose. Significant reduction in SOD activity was observed only at doses >= 100 mGy. Induction of oxidative stress in human blood due to irradiation was clearly evident from enhanced MDAcontent. Interpretation: This study indicates that exposure to ionizing radiation less than 100 mGy can cause genetic damage and induce oxidative stress. Furthermore, the results suggested that detection of genetic damage using MN assay is sensitive enough at a lower dose in contrast to IAEA manual where the detection limit is only 0.2-0.3 Gy.