Proceedings of the British Institute of Radiology

The “indirect effect” of ionizing radiation is believed to result from the production of oxidative species following the interaction of radiation with water. Dichlorofluorescin diacetate (DCFH-DA) is a heterocyclic compound which reacts with hydrogen peroxide in solution. It has been used to measure the production of metabolic oxidative products in polymorphonuclear blood cells. DCFH-DA freely diffuses into cells, whereupon hydrolysis to DCFH occurs thereby trapping the molecule within the cell. Reaction with hydrogen peroxide produced in water by ionizing radiation leads to the quantitative production of the highly fluorescent dichlorofluorescin. Fluorescence can then be measured by flow cytometry. We describe the use of DCFH-DA to measure intracellular oxidative products in human tumour cells following ionizing radiation treatment.