Influence of novobiocin on gamma-irradiated G(o)-lymphocytes as analyzed by cytogenetic endpoints

Experiments with novobiocin (NB) post-treatment were performed to verify it s effect on the frequencies of micronuclei (MN) and chromosomal aberrations (CA) induced by gamma-irradiation (0.75, 1.5 and 3.0 Gy) in human lymphocy tes at G(0)-phase. The frequencies of MN significantly decreased by 44 and 50%, for the treatment with NE 50 mu g/ml (30-min pulse) after radiation do ses of 1.5 and 3.0 Gy, respectively. However, CA frequencies were not signi ficantly affected. No significant effect on CA was observed when lymphocyte cultures were exposed to a single dose of 2.0 Gy at the G(0)-phase and pos ttreated with 25 mu g/ml NE for three hours either immediately after irradi ation (G(0)-phase) or after 24 h (S-phase). The significant suppressive eff ect of NE on MN frequencies supports the hypothesis that NE interaction wit h chromatin increases access to DNA repair enzymes.