The Use of Flow Cytometry in the Detection of Radiation- and Chemically Induced Nuclear Damage in Human Mononuclear Cells

Viable human mononuclear cells were treated with three known genotoxic agents, gamma radiation, bleomycin sulphate (BLM) and acetylaminofluorene (AAF). Following treatment, a high salt concentration buffer was used to disrupt the cells, releasing supercoiled DNA structures known as nucleoids. The nucleoids were treated with the fluorescent dye ethidium bromide, and exposed to a beam of laser light within a fluorescence activated cell sorter (FACS). Treatment of human mononuclear cells with the genotoxic agent BLM or with radiation prior to cell disruption and staining produced a dose-dependent increase in light scatter. However, treatment of human mononuclear cells with AAF, which requires metabolic activation, produced a dose response in light scatter that proved reversible and was not dependent on the formation of reactive metabolites. In the case of BLM and radiation, these changes in light scatter are interpreted as structural alterations in the nucleus partially induced by free radical attack, and thus provide an indication of the DNA damaging ability of the agent used. In contrast the reversible changes in light scatter seen with AAF may only indicate the ability of this agent to penetrate the genome. The significance of this reversible interaction with respect to genotoxicity is not known.