THE YIELD OF FISSION NEUTRON-INDUCED CHROMATID ABERRATIONS IN G2-STAGE HUMAN-LYMPHOCYTES - EFFECT OF CAFFEINE, HYDROXYUREA AND CYTOSINE-ARABINOSIDE POSTIRRADIATION

To evaluate the influence of inhibitors of DNA synthesis/repair on the yield of chromosomal aberrations in the G2 phase of the cell cycle, whole-blood cultures of human lymphocytes were exposed to various doses of fission neutrons or X-rays and treated post-irradiation during the last 2.45 h before harvesting, with 5 mm caffeine, 5 mm hydroxyurea (HU) and 0.05 mm cytosine arabinoside (ara-C). The presence of caffeine and HU strongly potentiated the yield of chromatid-type aberrations induced by both neutrons and X-rays. No potentiating effect, except at the highest dose of neutrons, was observed when irradiated cells were subsequently treated with ara-C. Since ara-C strongly potentiated the frequency of chromatid aberrations induced in G2 lymphocytes by X-rays, the results presented here indicate that fission neutrons produce a smaller proportion of lesions, the repair of which can be inhibited by ara-C, compared with the number produced by X-rays. In addition, neutron-induced mitotic delay was shortened by treatment with caffeine, mainly within the first 2 h after irradiation.