Abstract: Abstract: Objective To investigate the change of reference value for body weight、mortality、hematology and serum biochemistry of SD rats in test method of combined chronic toxicity / carcinogenicity study． Method 135 male and 138 female specific pathogen free SD rat of 4 weeks were selected． We measured the body weights once a week between 4 ～ 17 weeks of age and once four week between 18 ～ 108 weeks of age． The indexes of hematology and biochemistry of SD rats were measured at the age of 8 weeks old、30 weeks old、56 weeks old、82 weeks old、108 weeks old and record the mortality rate every day． Result The body weight of male rats was much higher than female rats from 6 weeks old． The 82 ～ 108 weeks of age was the rapid growth of mortality in rats． The coefficient of variation of indexes of hematology and biochemistry of male and female become larger with increasing age． Gender has a significant impact on hematology and serum biochemistry in rats． But the hematology and serum biochemistry which has significant difference between female and male become less with increasing age． Conclusion During the safety evaluation tests，expecially combined chronic toxicity / carcinogenicity study，both of gender and age have a greater impact on the body weight、hematology and serum biochemistry． Male and female should be separated from the statistics and the animals background data should be used at the same weeks．

Key words: combined chronic toxicity / carcinogenicity study, SD rats, body weight, mortality rate, hematology and
serum biochemistry, background data

摘要： 摘要: 目的研究两年慢性毒性联合致癌性试验中SD 大鼠的体质量、死亡率、血常规值和血生化值的变化。方法 SPF 级雄性SD 大鼠135 只，雌性138 只，4～ 17 周龄间每周测量体质量1 次，18 ～ 108 周龄间每4 周测定动物体 质量1 次并计算动物的死亡率; 分别于8 周龄、30 周龄、56 周龄、82 周龄和108 周采血，检测血常规和血生化指标。 结果雌性大鼠在6 ～ 108 周的体质量与雄性大鼠比较具有显著性差异( P ＜ 0. 05) ; 82 ～ 108 周龄是大鼠死亡率增 长的快速期。随着周龄的增加，雌鼠和雄鼠血液指标的变异系数增大。性别对大鼠的血常规和血生化指标具有明 显的影响，但雌鼠与雄鼠比较具有显著性差异的血液指标，随着周龄的增加而减少。结论在进行安全性评价试 验中，性别、周龄对SD 大鼠体质量、血常规值、血生化指标均有较大的影响，因此，雌雄宜分开统计，并需使用相同 周龄的动物背景数据作为参考值范围。

关键词: 慢性毒性联合致癌性试验, SD 大鼠, 体质量, 死亡率, 血常规值, 血生化值, 背景数据