Quantitative analysis of the induction of chromosome aberrations and sister-chromatid exchanges in human lymphocytes exposed to γ-rays and mitomycin-C in combination

Most chemicals are S-dependent and are potent inducers of SCE, but do not produce chromosome-type aberrations in the 1st metaphases after exposure. Ionizing radiation, which is an S-independent agent, produces chromosome-type aberrations. A series of experiments has been performed to investigate whether cytogenetic damage induced by ionizing radiation (γ-rays) might be assessed separately from that induced by the alkylating chemical, mitomycin-C (MMC), when human lymphocytes were exposed to these 2 agents in combination. Whole-blood cultures of human lymphocytes in G0 phase were exposed to γ-rays and MMC in combination or separately. Cytogenetic analyses were done for both chromosome aberrations (CA), analyzed in cultures incubated for 56 h without BrdUrd, and sister-chromatid exchanges (SCEs) in cultures incubated for 72 h with BrdUrd. The frequency of chromosome-type aberrations (dicentrics and rings) increased with increasing doses of γ-rays from 0.5 to 4.0 Gy. The dose-response relationships were the same with or without concomitant treatment with MMC (10-6 M). Although the SCE frequency increased with increasing doses of MMC, the increase was nearly the same as when cells were treated with both MMC and γ-rays (2 Gy). There was no interaction between MMC and γ-rays concerning these 2 endpoints. (author). 24 refs.; 4 tabs