title: DNA effects in repair-deficient V79 Chinese hamster cells studied with the comet assay.
abstract: Using the alkaline comet assay (single cell gel electrophoresis), we studied the induction and persistence of DNA damage induced by methyl methanesulfonate (MMS) and neocarzinostatin (NCS) in the repair-deficient Chinese hamster cell lines V-E5 and XR-V15B. Effects in the comet assay were analyzed directly after treatment as well as after a postincubation period in mutagen-free medium to gain insight into the DNA repair capacities of the mutant cell lines in relation to different primary DNA lesions. Both mutagens caused a concentration-related increase in DNA strand breakage in both mutant cell lines and in the normal parental cell lines. Repair of MMS-induced DNA damage during postincubation was similar in normal and mutant cell lines, while diminished repair was seen after NCS treatment in XR-V15B cells. Our data show that XR-V15B cells only repaired about 30% of NCS-induced DNA damage within 1 h, while the parental V79 cell line repaired about 70%. Since this cell line is defective in the repair of DNA double-strand breaks (DSB), the results indicate that NCS-induced DSB significantly contribute to the genotoxic effects seen in the comet assay. However, compared to previously studied induction of gene mutations and chromosome aberrations, detection of NCS-induced DNA effects with the comet assay was less sensitive and increased DNA migration only occurred under strong cytotoxic conditions.
authors.affiliation: Universität Ulm, Abteilung Medizinische Genetik, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Helbig
authors.forename: G
authors.initials: G
authors.lastname: Speit
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D002460:Cell Line / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D006224:Cricetinae; D004249:DNA Damage / Q000187:drug effects*; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D004586:Electrophoresis / Q000379:methods*; D008741:Methyl Methanesulfonate / Q000494:pharmacology*; D009153:Mutagens / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000633:toxicity; D013997:Time Factors; D009353:Zinostatin / Q000633:toxicity*
chemical_list: D018906:Antineoplastic Agents, Alkylating; D009153:Mutagens; D019384:Nucleic Acid Synthesis Inhibitors; D009353:Zinostatin; D008741:Methyl Methanesulfonate