title: DNA repair processes in germ cells demonstrated in ejaculated sperms of rabbits treated with methyl methane sulfonate.
abstract: Male rabbits were treated with a single i.v. injection of 22.5 mg/kg methyl methane sulfonate (MMS). 0--24 h later [3H]-thymidine was injected in both testicles. Incorporation of the isotope in germ cell DNA was demonstrated in ejaculated sperms. In controls labeled sperms were demonstrated first on day 40--43. These cells were in the preleptotene spermatocyte phase at the time of [3H]-thmidine injection. In rabbits treated with MMS significant radioactivity occurred in sperms collected from day 19 onwards. These cells were in late spermatocyte and early spermatid phase of maturation when [3H]-thymidine was injected. Incorporation of thymidine in these cell populations is interpreted as an expression of unscheduled DNA synthesis, a repair process initiated after chemical damage of germ cell DNA by MMS. The usefulness of the rabbit test system within the framework of conventional mutagenicity screening tests is discussed.
mesh_terms: D000818:Animals; D004260:DNA Repair / Q000187:drug effects*; D005854:Germ Cells / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008698:Mesylates / Q000494:pharmacology*; D008741:Methyl Methanesulfonate / Q000494:pharmacology*; D011817:Rabbits; D013094:Spermatozoa / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors
chemical_list: D008698:Mesylates; D008741:Methyl Methanesulfonate; D013936:Thymidine