ICR小鼠体内染色体畸变试验的优化

目的 使用ICR小鼠开展体内染色体畸变实验，通过在不同时间点给予环磷酰胺(cyclophosphamide，CP)及秋水仙素(colchicine,COL)，对比不同给药/取材时间点及不同给药浓度对小鼠骨髓细胞染色体畸变发生率的影响。方法 共36只约7～8周龄ICR雄性小鼠首先随机分为药后18 h取材组和给药后24 h取材组，再下设COL 4 mg/kg体质量(取材前4 h，i.p.)和10 mg/kg(取材前2 h,i.p.)给药组，以0.9% 氯化钠注射液为溶媒对照，分别给予CP 0 mg/kg、10 mg/kg和40 mg/kg，每小组各3只动物。记录实验期间给药前后动物体质量。阴性对照组和10 mg/kg CP组间隔24 h分两次给药,40 mg/kg CP为单次给药。给药后18 h或24 h取材，取材前2 h或4 h分别腹腔注射COL。取材时摘取全部实验动物双侧股骨，收集骨髓细胞悬液制备Giemsa染色体标本用于分析染色体畸变类型，并计算每组平均结构畸变细胞率(不含ctg及csg，AC%)、结构畸变细胞率(含ctg及csg，ACG%)、多畸变细胞率(不含ctg及csg，MAC%)及多倍体细胞率(PC%)。结果 本研究所用CP和COL对动物体质量无明显影响，给药剂量和给药频率可行。与各小组内的溶媒对照组相比，所有CP给药组的AC%、AGC%和MAC%均显著性升高(P<0.01)，且给药剂量高时染色体损伤更为严重；CP18 h-COL4h组的AC%、ACG%和MAC%均低于CP18 h-COL2h组，并存在显著性差异(P<0.05)，提示使用高剂量的COL(10 mg/kg)可产生额外的染色体损伤。溶媒对照组中的结构性畸变类型绝大多数为裂隙，而染色体单体及染色体断裂是CP引起的最主要畸变类型。结论 开展ICR小鼠染色体畸变试验时，在CP给药后约18 h、COL给药后4 h取材较为理想。本研究通过对试验条件的摸索不但积累了背景数据，也为相关研究者提供借鉴。

Optimization of Chromosome Aberration Test in ICR Mice

Objective To perform in vivo chromosome aberration test using ICR mice by administrated with cyclophosphamide (CP)and colchicine (COL)at different time points,and compare the effects of different administration and sampling strategies on the incidence of mouse bone marrow chromosomal aberrations.Method A total of 36 ICR male mice of about 7-8 weeks old were primarily randomly divded into 18 h and 24 h sampling group after the last dosing.Both groups werer further divided into COL 4 mg/kg (4 h before sampling,i.p.)and COL 10 mg/kg (2 h before i.p.)administration groups.In each group,the 0.9% sodium chloride injection was used as the vehicle control,and respectively dosed with 0 mg/kg,10 mg/kg,and 40 mg/kg CP for 3 animals each.The body weights of animals before and after administration during the experiment were recorded.The negative control group and the 10 mg/kg CP group were administered twice at a interval of 24 hours,and the 40 mg/kg CP was administered once.Both femurs of each animals were taken at 18 h or 24 h after the last administration for preparing bone marrow suspension,and COL was intraperitoneally injected 2 h or 4 h before the sampling.Slides with bone marrow samples were prepared and stained with Giemsa for identifying the types of chromosome aberrations,and the average structural aberration cell rate (excluding ctg/csg,AC%),structural aberration cell rate (including ctg/csg,ACG%)rate of cells with multiple aberrations (excluding ctg/csg,MAC%)and polyploid cell rate (PC%)were calculated.Result CP and COL used in this study showed no effect on the body weights of animals,and the administration doses and frequency are feasible.Compared with the vehicle control groups,AC%,AGC%,and MAC% of all CP administered groups were significantly increased (P<0.01)as higher CP dose showed more serious aberrations;AC%,ACG% and MAC% of CP18 h-COL4h group were significantly lower than the CP18 h-COL2h group (P<0.05),suggesting that high doses of COL (10 mg/kg)could produce additional chromosomal damage.Most of the structural aberration types in the vehicle control group were gaps,while chromatid and chromosome breakage were the most dominant aberration types induced by CP.Conclusion It is ideal to take the bone marrow sample 18 hours after administrated with CP and 4 hours after dosed with COL (4 mg/kg)for chromosome aberration test in mice.This study accumulated background data for the exploration of test conditions,and also provided reference for relevant researchers.