title: A method to quantify spontaneous and in vivo induced thioguanine-resistant mouse lymphocytes.
abstract: A clonogenic assay to quantify thioguanine (TG)-resistant (TGr) spleen lymphocytes in the mouse has been developed to support studies of in vivo mutation affecting the hypoxanthine phosphoribosyltransferase (hprt) locus. Lymphocytes are cultured in 96-well microtiter plates for 9 days with proliferation initiated by the mitogen concanavalin A and supported thereafter by conditioned medium containing interleukin-2. Lymphocytes are plated at high densities (4-8 X 10(5)/well) with TG and irradiated L5178Y lymphoma cells (10(4)/well) to detect the presence of TGr cells. To determine the cloning efficiency without TG lymphocytes are plated at a low density (10/well) with irradiated L5178Y cells and irradiated lymphocytes (4-8 X 10(5)/well). Proliferation of cells is detected by [3H]thymidine incorporation and scintillation spectrometry. Spontaneous frequencies of TGr clones are independent of TG dose from 0.2 to 10 micrograms/ml and independent of cell density over the range cited. The TGr clones tested have less than 10% hypoxanthine incorporation in vivo relative to unselected clones and have stable phenotypes in the absence of selection. The spontaneous frequency of TGr cells ranged from 1 to 3 X 10(-6). In vivo treatment of mice intraperitoneally with ethylnitrosourea 15 days prior to in vitro culture resulted in a linear dose-related increase of TGr cells, with 70.2 mg/kg inducing a frequency of TGr cells of 2 X 10(-5).
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005038:Ethylnitrosourea / Q000633:toxicity; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D008297:Male; D051379:Mice; D009152:Mutagenicity Tests / Q000379:methods*; D009154:Mutation / Q000187:drug effects*; D051381:Rats; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects*; D013866:Thioguanine / Q000494:pharmacology
chemical_list: D007041:Hypoxanthine Phosphoribosyltransferase; D013866:Thioguanine; D005038:Ethylnitrosourea