Adaptive response induced by low doses of ionizing radiation in human lymphocytes

LIBKIND FRATI, DIEGO; DURAND, J; BUNGE, MM; GILLETE, V

Recife, Brasil

Congreso; V Regional Congress on Radiation Protection and safety. II Iberian and Latin American Congress of Radiological Protection Societies; 2001

The term adaptive response (AR) applies to the phenomenon of protection or enhanced repair induced by a small dose of a mutagenic agent. In order to determine the existence of AR in human lymphocytes for two different irradiation schemes, microcultures of blood from 4 donors were irradiated. Samples were exposed 24 hours (hr) after phytohemagglutinin stimulation to an adapting dose of 0,01Gy and to a challenging dose of 1,5Gy either 6 or 24 hr later (irradiation scheme 24+30 or 24+48, respectively). Gamma radiation from a 2,5 MeV LINAC was used in all experiments. A cytogenetic analysis of unstable chromosome aberrations was applied as the endpoint. High inter-individual variability was found for the first irradiation scheme: one expressed AR, two did not and the last showed an apparent synergistic response. For the second irradiation scheme, low mitotic indices (MI) were found, suggesting a G2 arrest. When a series of harvesting times were applied for the last donor, normal MI were obtained only harvesting after 58 hr. An AR was found when harvesting at 72 hr but not at 58 hr.