title: Mitogenic stimulation may induce an anti-mutagenic repair system in human lymphocytes.
abstract: The effect of mitogenic stimulation prior to X-irradiation was studied in human lymphocytes using a cloning technique. The hypoxanthine phosphoribosyltransferase locus was monitored and mutant cells were selected by their ability to form a clone in the presence of 6-thioguanine. Survival and mutagenesis were studied for cells irradiated before phytohaemagglutinin (PHA) stimulation and 1-7 days after PHA stimulation. Prior mitogenic stimulation had no effect on the decreasing survival observed with increasing X-ray dose. The mean mutation frequency of unirradiated cells ranged from 1.8 x 10(-6) to 3.3 x 10(-6). Cells irradiated and then stimulated with PHA showed an increase in mutation frequency with increasing dose of X-rays, up to 9.5 x 10(-5) after 400 rad, but mitogenic stimulation with PHA on days 2 or 3 before irradiation completely, and on days 1, 5 or 7 almost completely, prevented induction of mutations by 300 rad. These results suggest that mitogenic stimulation activates an anti-mutagenic system which prevents pre-mutational lesions produced by X-irradiation being transformed into mutations. The lack of effect of PHA stimulation on survival suggests that the types of damage leading to mutations and lethality are different.
authors.affiliation: Department of Haematology, Flinders Medical Centre, Bedford Park, Australia.
authors.forename: B J
authors.initials: BJ
authors.lastname: Sanderson
authors.forename: A A
authors.initials: AA
authors.lastname: Morley
mesh_terms: D002478:Cells, Cultured; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects*; D009154:Mutation; D013866:Thioguanine / Q000494:pharmacology*; D014965:X-Rays
chemical_list: D013866:Thioguanine