title: Evaluation of lacI mutation in germ cells and micronuclei in peripheral blood after treatment of male lacI transgenic mice with ethylnitrosourea, isopropylmethane sulfonate or methylmethane sulfonate.
abstract: Male C57B1/6 lacI transgenic mice were used to evaluate germ cell mutagenesis in vivo as part of a collaborative study. Groups of 10 mice were administered single intraperitoneal doses of ethylnitrosourea (ENU; 150 mg/kg), isopropyl methanesulfonate (IPMS; 200 mg/kg), methyl methanesulfonate (MMS; 40 mg/kg) or vehicle. Epididymal spermatozoa and testes were recovered 3 days later and DNA isolated subsequently from epididymal spermatozoa and seminiferous tubules were analyzed for lacI mutations. The mutant frequency in seminiferous tubules (average +/- SEM) increased significantly compared with untreated controls (7.2 +/- 0.7 x 10(-5) following treatment with ENU (11.7 +/- 0.8 x 10(-5), p = 0.003) or with IPMS (9.6 +/- 0.5 x 10(-5), p = 0.018) but not following treatment with MMS (8.1 +/- 0.8 x 10(-5), p = 0.213). Group mutant frequencies were not determined for epididymal spermatozoa from MMS- or IPMS-treated mice because of poor DNA recoveries. As another indicator of the genotoxicity of these alkylating agents, the frequencies of micronuclei were determined in the peripheral blood 48 h after carcinogen administration in the same transgenic mice. The micronuclei frequencies were elevated significantly (p < 0.05) by each treatment (IPMS: 1.0%; MMS: 0.94%) compared to vehicle controls (0.3%). In a separate experiment, 40 mg/kg ENU was previously found to increase the frequency of micronuclei in peripheral blood of lacI transgenic mice 48 h after treatment (3.2%; Gibson et al., 1995). These results demonstrate that the lacI transgenic mouse male germ cells are sensitive to some, but not all, mutagens under the conditions used in this experiment. Investigation of other experimental designs would offer additional perspective on the usefulness of this transgenic model for routine mutagenicity testing in germ cells.
authors.affiliation: Procter and Gamble Company, Cincinnati, OH 45253-8707, USA.
authors.forename: N J
authors.initials: NJ
authors.lastname: Gorelick
authors.forename: J L
authors.initials: JL
authors.lastname: Andrews
authors.forename: D P
authors.initials: DP
authors.lastname: Gibson
authors.forename: G J
authors.initials: GJ
authors.lastname: Carr
authors.forename: M J
authors.initials: MJ
authors.lastname: Aardema
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D004822:Epididymis / Q000166:cytology; D029968:Escherichia coli Proteins; D005038:Ethylnitrosourea / Q000633:toxicity*; D056968:Lac Repressors; D008297:Male; D008698:Mesylates / Q000633:toxicity*; D008741:Methyl Methanesulfonate / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D015162:Micronucleus Tests; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D012097:Repressor Proteins / Q000235:genetics*; D012671:Seminiferous Tubules / Q000166:cytology; D013094:Spermatozoa / Q000187:drug effects*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D056968:Lac Repressors; D008698:Mesylates; D009153:Mutagens; D012097:Repressor Proteins; D008741:Methyl Methanesulfonate; D005038:Ethylnitrosourea; C002531:isopropylmethanesulfonate