Evaluation of the effect of 90Sr β-radiation on human blood cells by chromosome aberration and single cell gel electrophoresis (comet assay) analysis

Among various environmental genotoxins, ionizing radiation has received special attention because of its mutagenic, carcinogenic and teratogenic potential. In this context and considering the scarcity of literature data, the objective of the present study was to evaluate the effect of Sr-90 beta -radiation on human cells. Blood cells from five healthy donors were irradiated in vitro with doses of 0.2-5.0 Gy from a 90Sr source (0.2 Gy/min) and processed for chromosome aberration analysis and for comet assay. The cytogenetic results showed that the most frequently found aberration types were acentric fragments, double minutes and dicentrics. The alpha and beta coefficients of the linear-quadratic model, that best fitted the data obtained, showed that Sr-90 beta -radiation was less efficient in inducing chromosome aberrations than other types of low linear energy transfer (LET) radiation such as H-3 beta -particles, Co-60 gamma -rays, Cs-137 and Ir-192 and X-rays. Apparently, Sr-90 beta -radiation in the dose range investigated had no effect on the modal chromosome number of irradiated cells or on cell cycle kinetics. Concerning the comet assay, there was an increase in DNA migration as a function of radiation dose as evaluated by an image analysis system (tail moment) or by visual classification (DNA damage). The dose-response relation adequately fitted the non-linear regression model. In contrast to the cytogenetic data, 90Sr beta -radiation induced more DNA damage than 60Co gamma -radiation when the material was analyzed immediately after exposures. A possible influence of selective death of cells damaged by radiation was suggested. (C) 2001 Elsevier Science B.V. All rights reserved.