PERSISTENCE OF RADIATION-INDUCED TRANSLOCATIONS IN RAT PERIPHERAL-BLOOD DETERMINED BY CHROMOSOME PAINTING

In this article, we address the issue of persistence of chromosome exc hanges following acute in vitro exposure of mt peripheral blood to Cs- 137. Irradiation occurred 24 hr after culture initiation, and metaphas e chromosomes were prepared 2, 3, 4, and 5 days later. Chromosomes 1, 2, and 4 were painted in unique colors and scored for structural aberr ations. Dicentric chromosomes and acentric fragments diminished rapidl y with time, as expected. Translocations exhibited greeter persistence , but still showed a reduction in frequency, reaching a plateau of app roximately 65 and 55% of their initial values, 4 days after exposure t o 1 and 2 Gy, respectively. An exponentially declining model was fit t o the combined dicentric, acentric fragment, and translocation frequen cies, which showed that ail three aberration types declined at equival ent rates. The frequencies of dicentrics and fragments declined to a p lateau of zero, while translocations reached a plateau at frequencies significantly greater than zero. The decline in translocations with ti me is inconsistent with prevailing theoretical expectations, but is co nsistent with a model where some translocations are fully stable (pers istent) and some are unstable (not persistent) through cell division. These results may have implications for radiation biodosimetry in huma ns. (C) 1997 Wiley-Liss, Inc.