Alpha coefficient of dose-response for chromosome translocations measured by FISH in human lymphocytes exposed to chronic ⁶⁰Co gamma rays at body temperature

Purpose: To measure the alpha coefficient, the initial slope of the translocation dose-response curve, for ⁶⁰Co γ-rays in human lymphocytes. Materials and methods: Human lymphocytes were exposed to 0, 0.32, 0.62 and 0.92 Gy of chronic ⁶⁰Co γ-rays under conditions that reduce the metabolic stress to the cells. Chromosome translocation frequencies were measured using fluorescence in situ hybridization with a whole-chromosome probe cocktail specific for chromosomes 1, 2, 4 (orange) and 3, 5, 6 (green). Results: A total of 72 383 metaphases were analysed (33 429 in exposed cells) in two individuals. The shape of the dose-response curves for translocations was linear, and alpha coefficient was measured as 0.024 ± 0.002 translocations per cell per Gy for the combined data for two 24 year old male donors. Conclusion: The alpha coefficients measured after chronic exposure were in good agreement with that reported in the literature for acute, low-dose exposure of human lymphocytes to ⁶⁰Co γ-rays.