title: Mutagenicity of 2-amino-N6-hydroxyadenine at the tk locus in L5178Y strains differing in repair capabilities and karyotype.
abstract: The cytotoxicity and mutagenicity of 2-amino-N6-hydroxyadenine (AHA) were measured in strains of L5178Y differing in repair capabilities and karyotype. Strain LY-R83 is monosomic for chromosome 11 and is therefore hemizygous for the tk gene, while strains LY-R16 and LY-S1 are TK+/- heterozygotes. Both strain LY-R83 and LY-R16 are sensitive to UV light and are presumed to be deficient in the excision of pyrimidine dimers as shown for the parental strain, LY-R (Hagen et al., 1988; Szumiel et al., 1988). Strain LY-S1 is sensitive to the cytotoxic effects of ionizing radiation and is presumed to be defective in the repair of radiation-induced DNA double-strand breaks, as shown for the parental strain, LY-S (Evans et al., 1987a; Wlodek and Hittelman, 1987). The sensitivities of the three strains to the cytotoxic effects of AHA were similar. After a 4-hour treatment with AHA at 37 degrees C, the D37 for all three strains was approximately 35 ng/ml. The AHA-induced mutant frequency was similar for the hemizygous TK+ strain LY-R83 and the heterozygous TK +/- strain LY-R16, but was slightly higher for strain LY-S1 than for either LY-R strain at an AHA concentration of 100 ng/ml. The proportion of AHA-induced LY-S1 TK -/- mutants forming colonies with diameters less than 0.3 mm was much lower than following treatment with X radiation (24% vs. 61% for AHA and X radiation, respectively). These results indicate that the vast majority of AHA-induced TK -/- mutants harbor single gene mutations. AHA did not result in cyanide-insensitive oxygen uptake, and treatment with this compound did not induce a significant number of DNA single-strand breaks, DNA alkali labile lesions, or DNA degradation in either strain. However, two hours after AHA removal, DNA single-strand breaks and/or alkali-labile lesions, possibly due to the occurrence of DNA repair, were apparent in the DNA of both strain LY-R16 and strain LY-S1.
authors.affiliation: Department of Radiology, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: H H
authors.initials: HH
authors.lastname: Evans
authors.forename: J
authors.initials: J
authors.lastname: Mencl
authors.forename: M
authors.initials: M
authors.lastname: Ricanati
authors.forename: C
authors.initials: C
authors.lastname: DiSalvo
authors.forename: M E
authors.initials: ME
authors.lastname: Varnes
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D004260:DNA Repair; D005609:Free Radicals; D008223:Lymphoma; D051379:Mice; D009152:Mutagenicity Tests; D009153:Mutagens; D010101:Oxygen Consumption; D013937:Thymidine Kinase / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D005609:Free Radicals; D009153:Mutagens; C030632:2-amino-N(6)-hydroxyadenine; D013937:Thymidine Kinase; D000225:Adenine