title: Effect of dose fractionation on the ethylnitrosourea induction of specific-locus mutations in mouse spermatogonia.
abstract: As measured by specific-locus mutations in mouse spermatogonia, fractionating a dose of 100 mg of ethylnitrosourea per kg of body weight into doses of 10 mg/kg injected intraperitoneally at weekly intervals greatly reduces the mutation frequency compared with that from a single dose of 100 mg/kg. Because there is independent evidence that the doses of 10 and 100 mg/kg reach the germ cells in amounts directly proportional to the injected dose, the lower mutational response with the fractionated dose is attributed to repair. The induced mutation rate expected from a single 10-mg/kg dose (on the assumption that this would be 1/10th the rate observed after 10 such doses) would be only 75% of the spontaneous mutation rate. Mouse spermatogonia apparently have an efficient repair system that is effective even against a potent mutagen.
mesh_terms: D000483:Alleles; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005038:Ethylnitrosourea / Q000008:administration & dosage*; D008297:Male; D051379:Mice; D009154:Mutation / Q000187:drug effects*; D009607:Nitrosourea Compounds / Q000008:administration & dosage*; D013093:Spermatogonia / Q000187:drug effects*; D013094:Spermatozoa / Q000187:drug effects*
chemical_list: D009607:Nitrosourea Compounds; D005038:Ethylnitrosourea