Cytotoxic and Mutagenic Effects of Radon and Radon Daughters on Murine L5178Y Lines Differing in DNA Repair

• Published in: Radiation research 1993-10, Vol.136 (1), p.57-64
• Main Authors: Evans, H. H., Mencl, J., Hui, T. E., Ricanati, M., Horng, M. F., Di Salvo, C., Bakale, G., Rao, P. S.
• Format: Article
• Language: English
• Subjects: Alleles; Animals; Biological and medical sciences; Biological effects of radiation; Cell Line; Cell lines; Cell Survival - radiation effects; CHO cells; Chromosome Deletion; Cultured cells; DNA; DNA Repair; Fundamental and applied biological sciences. Psychology; Galactokinase - metabolism; Genetic mutation; Ionizing radiations; Lesions; Mice; Mutagenesis; Radiation dosage; Radiation tolerance; Radon; Radon - toxicity; Radon Daughters - toxicity; Thymidine Kinase - genetics; Tissues, organs and organisms biophysics
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3578640

The effects of 222 Rn were measured in mouse L5178Y (LY) lymphoblasts that differ in repair capabilities. Line LY-S1 is deficient in the repair of X-radiation-induced DNA double-strand breaks, while lines LY-R16 and LY-R83 are presumed to be deficient in the excision of UV-radiation-induced pyrimidine dimers. Line LY-R83 is hemizygous while the other two lines are heterozygous at the thymidine kinase (tk) locus. After exposure to radon the $D_{0}\text{'}{\rm s}$ were found to be very similar for the three lines (0.30-0.31 Gy), whereas for X radiation the D0 for line LY-S1 is lower (0.7 Gy) than that for the two LY-R lines (1.3 Gy). Mutant frequencies at the tk locus were higher per gray after treatment with radon than X radiation, but at equitoxic doses the mutant frequencies were similar for X and α-particle radiation. A low radon-induced mutant frequency was observed for the hemizygous line, in agreement with the hypothesis that multilocus lesions were induced by the α-particle radiation and that mutants bearing intergenic lesions were not recovered in the ${\rm TK}^{+/-}$ line. The entire active tk allele was lost by 81% of the ${\rm TK}^{-/-}$ mutants of line LY-R16. In lines LY-S1 and LY-R16, 39-43% of the ${\rm TK}^{-/-}$ mutants exhibited loss of galactokinase activity, indicating that the mutational lesion inactivating the tk gene frequently extended to the neighboring galactokinase gene.