INCREASED HPRT MUTANT FREQUENCIES IN BRAZILIAN CHILDREN ACCIDENTALLY EXPOSED TO IONIZING-RADIATION

We have examined the effects of ionizing radiation on somatic mutation s in vivo, using the hprt clonal assay. The study was performed on blo od samples obtained from children exposed during a radiological accide nt that happened in 1987, in Goiania, Brazil. The group of children ex posed to ionizing radiation includes six males and four females rangin g in age from 6 to 14 years at the time of exposure. The radiation dos es ranged from 15 to 70 cGy. A Brazilian control group, not exposed to ionizing radiation, was also analyzed under similar conditions. The m ean hprt mutant frequency for the exposed group was 4.6 times higher t han the control group, although the cloning efficiency from the expose d group was significantly reduced. Linear regression analysis of the m utant frequency and ionizing radiation dose did not show a significant relationship between these two parameters. However, a reliable invers e relationship was demonstrated when the regression analysis was perfo rmed with nonselective cloning efficiency and ionizing radiation dose. It was demonstrated that nonselective cloning efficiency diminishes a s ionizing radiation dose increases. To correct mutant frequencies for clonal events, the clonal relationship between the hprt mutant clones was examined by T-cell receptor analysis. The majority of the mutants analyzed represented individual clones, thus validating the observed mutant frequencies. (C) 1996 Wiley-Liss, Inc.