中文摘要：

目的：研究不同剂量大豆异黄酮（soy isoflavones,SI）对二甲基苯蒽（7,12-dimethyl-benz（a）anthracene,DMBA）诱导的去势大鼠和正常大鼠乳腺肿瘤发生率的影响。方法：将96只雌性SD大鼠随机分到去势组和正常组,每组各48只,去势组大鼠行双侧卵巢切除术,随后根据体重水平随机将去势大鼠和正常大鼠各分为空白对照组、阳性对照组、雌激素对照组、SI高（100mg/kg）、中（50mg/kg）、低剂量组（10mg/kg）,每组8只,除两个空白对照组外,每组大鼠经口给予5mg DMBA,每周触诊大鼠乳腺肿瘤发生情况并记录体重和摄食量。24周后处死大鼠,观察各组大鼠乳腺肿瘤的发病率并检测大鼠血浆中超氧化物歧化酶（SOD）活力和丙二醛含量水平。结果：去势大鼠SI高、中、低剂量组乳腺肿瘤发病率与阳性对照组相比,差异没有统计学意义（P〉0.05）,并且SOD活力水平显著低于阳性对照组（P〈0.01）;而正常大鼠SI高、中剂量组乳腺肿瘤发病率显著低于阳性对照组（P〈0.01）,并且SOD活力水平也显著高于阳性对照组（P〈0.01）。结论：50mg/kg和100mg/kg SI能够显著降低正常大鼠的乳腺肿瘤发病率,此作用可能与其升高正常大鼠机体内SOD的活力有关,而SI对去势大鼠的乳腺肿瘤发病率降低不显著,并且显著抑制大鼠血浆SOD活力,推测SI对去势/正常大鼠乳腺肿瘤发病率和抗氧化功能的影响可能与大鼠体内雌激素水平变化有关。

英文摘要：

Objective：To study the effect of soy isoflavones（SI）at various doses on the incidence of breast tumors induced by 7,12-dimethyl-benz（a）anthracene（DMBA）in ovariectomized and normal rats.Methods：96 SD female rats were randomly divided into ovariectomized group and normal group.Rats in the former group were ovariectomized,then those in each group were randomly placed into six subgroups：blank control,positive control,estrogen control,SI of high dose（100 mg/kg SI）,moderate dose（50 mg/kg SI）and low dose（10 mg/kg SI）group according to the body weight.All rats received a single oral dose of 5 mg DMBA,except for the blank control and were palpated weekly to monitor the tumor development.Body weight and diet intake were also recorded weekly.Rats were executed 24 weeks after DMBA administration,the incidence of breast tumors in each group was computed and the activities of superoxide dismutase（SOD）and contents of malondialdehyde（MDA）in rats＇ plasma were examined.Results：Compared with the positive group,incidence of breast tumors in ovariectomized rats at high,moderate and low dose SI group was not statistically different（P0.05）,and the activities of SOD in those groups were statistically lower（P0.01）;however,incidence of breast tumors in normal rats at high and moderate dose SI group was statistically different from the positive group（P0.01）,and the activities of SOD in those groups were statistically higher（P0.01）.Conclusion：SI of 50 mg/kg and 100 mg/kg could decrease the incidence of breast tumors in normal rats,which may be related to the higher activities of SOD induced by SI;however,SI could not decrease the incidence of breast tumors and inhibit the activities of SOD in ovariectomized rats.The effects of SI on the incidence of breast tumors and antioxidant activities may be influenced by different basal levels of estrogen in ovariectomized and normal rats.