title: Measurement of in vivo mutant frequency in lymphocytes in the mouse.
abstract: A limiting-dilution cloning technique for quantifying in vivo mutations at the hypoxanthine phosphoribosyl transferase locus in mouse splenocytes was developed. Mouse splenocytes were cultured in round-bottom microwells with irradiated feeder cells, concanavalin A, and a source of interleukin 2 at five cells/well in the absence of thioguanine, and at 5 X 10(4) cells/well in the presence of 2.5 micrograms/ml thioguanine; mutant frequency was calculated as the ratio of the cloning efficiencies with or without thioguanine. The geometric mean (95% range) for the mutant frequency in 20 mice was 1.54 X 10(-6) (4.7 X 10(-7) -2.6 X 10(6)) and whole-body X-irradiation resulted in a dose-related increase in mutant frequency of up to approximately 20 times the baseline level. The in vivo murine mutation assay should be a useful system for genotoxicity testing and may be of particular value in establishing risk estimates for human populations exposed to genotoxins.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D003208:Concanavalin A / Q000494:pharmacology; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D007376:Interleukin-2 / Q000494:pharmacology; D008214:Lymphocytes / Q000187:drug effects* / Q000201:enzymology / Q000528:radiation effects; D051379:Mice; D009152:Mutagenicity Tests; D013154:Spleen / Q000166:cytology; D013866:Thioguanine / Q000378:metabolism; D014916:Whole-Body Irradiation
chemical_list: D007376:Interleukin-2; D003208:Concanavalin A; D007041:Hypoxanthine Phosphoribosyltransferase; D013866:Thioguanine