AN ANALYSIS OF GAMMA-RAY-INDUCED DNA-DAMAGE IN HUMAN BLOOD LEUKOCYTES, LYMPHOCYTES AND GRANULOCYTES

Lymphocytes and granulocytes were separated from human peripheral blood and irradiated with low doses of gamma-rays (0.05-0.5 Gy) from a Cs-137 source. The magnitude and intercellular distribution of DNA damage, i.e., single-strand breaks and alkali-labile lesions, were compared with those obtained in unfractionated leukocytes irradiated in whole blood, using the alkaline single-cell gel-electrophoresis technique. Based on the extent of DNA migration, irradiation resulted in a linear and dose-dependent increase in DNA damage in all 3 cell populations, with a significant increase being detected at 0.05 Gy. The dose-dependent increase for DNA migration was not significantly different between separated lymphocytes and granulocytes, but their responses were significantly elevated over that obtained for leukocytes irradiated in whole blood. Based on an analysis of the ratio of the range to the standard deviation for each cell population at each dose of radiation, the distribution of damage among cells was relatively homogeneous and independent of dose and cell population. These results are consistent with a hypothesis that irradiation of leukocytes in whole blood partially protects against radical-induced DNA damage.