The magnitude of the radioadaptive response: the search for a possible energy dependency?

Human lymphocytes pretreated with low doses of ionizing radiation become less susceptible to genetic damages induced by subsequent high doses of radiation. A major part of medical irradiations are diagnostic radiographies which are usually performed with 50-150 kVp X-rays. The cytogenetic adaptive response induced by low doses of X-rays with different energies in the diagnostic range (70 keV ≤ max ≤ 150 keV) was studied using cultured human lymphocytes of four healthy young blood donors aged from 19 to 41. Lymphocytes were irradiated with 5 cGy of X-rays at 0.247 Gy/min at 24 h of culture and then irradiated with 2 Gy at 48 h. The cells were harvested 6 hours later and chromosome aberrations were measured. Despite the fact that our preliminary results show that high energy X-rays (Emax =150 keV) can induce the most efficient adaptive response, statistical analysis of data indicates that the induction of adaptive response is possibly no dependent on the X-ray photon energies up to 150 keV. Furthermore, our results show that due to inter-individual variations, there is a considerable variation among the magnitude of induced adaptive response in these four blood donors. (author)