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  • Title: Human and rodent cell lines showing no differences in the induction but differing in the repair kinetics of radiation-induced DNA base damage.
    Author: Purschke M, Kasten-Pisula U, Brammer I, Dikomey E.
    Journal: Int J Radiat Biol; 2004 Jan; 80(1):29-38. PubMed ID: 14761848.
    Abstract:
    PURPOSE: To compare the induction and repair of radiation-induced base damage in human and rodent cell lines. MATERIAL AND METHODS: Experiments were performed with two human (normal fibroblasts HSF1 and tumour HeLa cells) and two rodent (mouse L929 and hamster CHO-K1) cell lines. Base damage was determined with the alkaline comet assay combined with the repair enzyme formamidopyrimidine-glycosylase (Fpg). Proteins were detected by Western blot. RESULTS: The induction of Fpg-sensitive sites was measured in human and rodent cell lines for doses up to 8 or 5 Gy, respectively. Comets were analysed in terms of tail moments, which were transformed into Gy-equivalents. The amount of Fpg-sensitive sites increased linearly with doses up to 4 Gy, whereby the ratio of single-strand breaks (ssb) to Fpg-sensitive sites was nearly identical for human and rodent cells with ssb:Fpg-sensitive sites=1:0.41+/-0.07 and 1:0.45+/-0.05, respectively. For doses exceeding 4 Gy, the amount of Fpg-sensitive sites did not increase further, indicating a dose limit up to which the comet assay can be used to detect Fpg-sensitive sites. Repair of Fpg-sensitive sites was studied for an X-ray dose of 4 Gy. For all four cell lines, the repair was measured to be completed 24 h after irradiation, but with pronounced differences in the kinetics. In both rodent cell lines, 50% of Fpg-sensitive sites were removed after t((1/2))=25+/-10 min in contrast to t((1/2))=80+/-20 min in the two human cell lines. The two species also differed in the level of polymerase ss with, on average, a three- to fivefold higher level in rodent cells compared with human cells. CONCLUSIONS: Repair of radiation-induced Fpg-sensitive sites was much faster in rodent than in human cells, which might result from the higher level of polymerase ss found in rodent cells.
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