MODULATION OF RADIATION-INDUCED CHROMOSOMAL DAMAGE BY INHIBITORS OF DNA-REPAIR AND FLOW CYTOMETRIC ANALYSIS IN ATAXIA-TELANGIECTASIA CELLS WITH INTERMEDIATE RADIOSENSITIVITY

The relationship between repair processes and chromosomal aberrations and X-ray-induced cell cycle perturbations were investigated in ataxia telangiectasia (AT) cells with 'intermediate' (AT-INT) and 'classical ' radiosensitivity, In the cytogenetic experiments, three AT-INT lymph oblastoid cell lines were X-irradiated in G2-phase and incubated in th e presence of inhibitors of DNA polymerases alpha/delta/epsilon (cytos ine arabinoside, aphidicolin, 10% v/v DMSO), ribonucleotide reductase (hydroxyurea) and presumed inhibitors of protein kinases (caffeine), F low cytometric analysis was performed in cells harvested 20 h after ir radiation and stained with either propidium iodide or antibody against 5-bromodeoxiuridine in order to investigate cell cycle distribution f ocusing on G2/Mphase accumulation. From our data it appears that: (i) chromosomal sensitivity to radiation in AT does not always reflect cli nical features; (ii) the effects of DNA repair inhibitors are inversel y correlated with chromosomal radiosensitivity; and (iii) radiation-in duced G2/M phase accumulation is a feature of AT cells and not necessa rily correlated with cellular and chromosomal sensitivity to ionizing radiation.