Walker V E, Sisk S C, Upton P B, Wong B A, Recio L
Department of Pathology, University of North Carolina at Chapel Hill, 27599-7525, USA.
Mutat Res. 1997 Aug 14;392(3):211-22. doi: 10.1016/s1383-5718(97)00062-4.
Ethylene oxide (EO) is a direct-acting alkylating agent with the potential to induce cytogenetic alterations, mutations, and cancer. In the present study, the in vivo mutagenicity of EO at the hypoxanthine guanine phosphoribosyltransferase (hprt) locus of T-lymphocytes was evaluated following inhalation exposure of male B6C3F1 lacI transgenic mice. For this purpose, groups of male Big Blue mice at 6-8 (n = 4/group) and 8-10 (n = 5/group) weeks of age were exposed to 0, 50, 100, or 200 ppm EO for 4 weeks (6 h/day, 5 days/week). At necropsy, T-cells were isolated from thymus and/or spleen and cultured in the presence of concanavalin A, IL-2, and 6-thioguanine [Skopek, T.R., V.E. Walker, J.E. Cochrane et al. (1992) Proc. Natl. Acad. Sci. USA, 89, 7866-7870]. The time course for expression of hprt-negative lymphocytes in thymus was determined in mice necropsied 2 h, 2 weeks, and 8 weeks after exposure to 200 ppm EO. The dose-response for hprt mutant T-cells in thymus and spleen was defined in mice necropsied 2 and 8 weeks post-exposure, respectively. The hprt mutant frequency (Mf) in thymus of exposed mice was increased 2 h after exposure and reached a maximum of 7.5 +/- 0.9 x 10(-6) (average Mf +/- SE) at 2 weeks post-exposure, compared with 2.3 +/- 0.8 x 10(-6) in thymus of control mice. Dose-related increases in hprt Mfs were found in thymus from mice exposed to 100 and 200 ppm EO. In addition, a nonlinear dose-dependent increase in hprt Mfs was observed in splenic T-cells, with greater mutagenic efficiency (mutations per unit dose) found at higher concentrations than at lower concentrations of EO. Average induced Mfs (i.e. induced Mf = treatment Mf - background Mf) in splenic T-cells were 1.6, 4.6, and 11.9 x 10(-6) following exposures to 50, 100, or 200 ppm EO, respectively, while the average control Mf value was 2.2 +/- 0.3 x 10(-6). In aliquots of lymphocytes (both B- and T-cells) isolated from spleen for analysis of lacI mutations in the same animals, only two of three EO-exposed mice at the 200 ppm exposure level demonstrated an elevated lacI Mf and these elevations were apparently due to the in vivo replication of preexisting mutants and not due to the induction of new mutations associated with EO exposure [Sisk, S., L.J. Pluta, K.G. Meyer and L. Recio (1996) Mutation Res., submitted]. These data demonstrate that repeated inhalation exposures to high concentrations of EO produce dose-related increases in mutations at the hprt locus of T-lymphocytes in male lacI transgenic mice of B6C3F1 origin.
环氧乙烷（EO）是一种直接作用的烷基化剂，具有诱导细胞遗传学改变、突变和癌症的潜力。在本研究中，对雄性B6C3F1 lacI转基因小鼠进行吸入暴露后，评估了EO在T淋巴细胞次黄嘌呤鸟嘌呤磷酸核糖基转移酶（hprt）位点的体内诱变性。为此，将6 - 8周龄（每组n = 4）和8 - 10周龄（每组n = 5）的雄性大蓝鼠分组，暴露于0、50、100或200 ppm的EO中4周（每天6小时，每周5天）。尸检时，从胸腺和/或脾脏中分离出T细胞，并在伴刀豆球蛋白A、白细胞介素-2和6 - 硫鸟嘌呤存在的情况下进行培养[斯科佩克，T.R.，V.E.沃克，J.E. Cochrane等人（1992年）《美国国家科学院院刊》，89，7866 - 7870]。在暴露于200 ppm EO后2小时、2周和8周进行尸检的小鼠中，测定胸腺中hprt阴性淋巴细胞表达的时间进程。分别在暴露后2周和8周进行尸检的小鼠中，确定胸腺和脾脏中hprt突变T细胞的剂量反应。与对照小鼠胸腺中的2.3 +/- 0.8 x 10⁻⁶相比，暴露小鼠胸腺中的hprt突变频率（Mf）在暴露后2小时增加，并在暴露后2周达到最大值7.5 +/- 0.9 x 10⁻⁶（平均Mf +/-标准误）。在暴露于100和200 ppm EO的小鼠胸腺中发现hprt Mf与剂量相关增加。此外，在脾T细胞中观察到hprt Mf呈非线性剂量依赖性增加，在较高浓度的EO下比在较低浓度下具有更高的诱变效率（每单位剂量的突变数）。暴露于50、100或200 ppm EO后，脾T细胞中的平均诱导Mf（即诱导Mf = 处理Mf - 背景Mf）分别为1.6、4.6和11.9 x 十的负六次方，而平均对照Mf值为2.2 +/- 0.3 x 十的负六次方。在从脾脏分离的淋巴细胞（B细胞和T细胞）等分试样中分析同一动物的lacI突变时，在200 ppm暴露水平下，三只暴露于EO的小鼠中只有两只表现出lacI Mf升高，这些升高显然是由于预先存在的突变体在体内复制，而不是由于与EO暴露相关的新突变诱导[Sisk，S.，L.J. Pluta，K.G. Meyer和L. Recio（1996年）《突变研究》，待发表]。这些数据表明，对B6C3F1来源的雄性lacI转基因小鼠反复吸入高浓度EO会导致T淋巴细胞hprt位点的突变与剂量相关增加。
