PERSISTENT INCREASE IN THE RATES OF APOPTOSIS AND DICENTRIC CHROMOSOMES IN SURVIVING V79 CELLS AFTER X-IRRADIATION

In parallel to delayed reproductive death and delayed micronuclei in s urviving V79 cells that have been reported, the frequency of apoptosis and dicentrics was investigated in the same cell line, 1-2 weeks afte r X-ray doses between 1 and 12 Gy. Apoptosis was assessed by morpholog ical criteria after staining with Giemsa and using the Apoptag(TM) met hod in parallel. The frequency of apoptosis peaked 48 h after irradiat ion at about 35% as a function of dose and then decreased to about 10% on day 3. It remained 10 times higher than in unirradiated cells unti l day 14. The frequency of dicentric chromosomes 24 h after irradiatio n increased according; to a linear-quadratic function, up to about 110 % after 12 Gy, decreased 3 days later to about 10% and remained about 5-fold higher than in control cells. The dose-response relationship wa s similar for all the various end-points of expression of radiation in duced genomic instability, showing a steep increase of the frequency w ith dose up to 3-4 Gy and with no further increase at higher radiation doses.