HPRT mutant frequences from Brazilian children accidentally exposed to ionizing radiation
Date
1994
Authors
Saddi, Vera
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Abstract
To examine the effects of ionizing radiation on somatic mutations in vivo, the hprt clonal assay was performed on children accidentally exposed during a radiological accident that happened in 1987, in Goiania, Brazil. The group of children exposed to ionizing radiation includes six males and four females ranging in age from 6 to 14 years. The radiation doses to which they were exposed ranged from 15 to 70 cGrays. A Brazilian control group, not exposed to ionizing radiation, was also analyzed under similar conditions for the purpose of comparison. The mean hprt mutant frequency for the exposed group was 4.6 times higher than the control group, although the cloning efficiency for the exposed group was significantly reduced. Linear regression analysis of the mutant frequency and ionizing radiation dose did not show a significant relationship between these two parameters. However, a reliable inverse relationship was demonstrated when the regression analysis was performed with cloning efficiency and ionizing radiation dose. It was demonstrated that cloning efficiency diminishes as ionizing radiation dose increases.
To verify the clonal relationship between the hprt mutant clones isolated, T-cell receptor analysis was performed with a number of mutant clones. It was verified that the majority of the mutants analyzed represented individual clones, thus validating the mutant frequencies obtained. The hprt clonal assay proved to be sufficiently sensitive to detect somatic mutagenic effects caused by ionizing radiation in the exposed group of children. Nevertheless, a control group was required in order to compare the findings and to substantiate the observations.