硒对氧化偶氮甲烷所致大鼠结肠癌形成过程中垂体远侧部促肾上腺皮质激素阳性细胞的影响

目的观察硒对致癌剂氧化偶氮甲烷(AOM)所致大鼠结肠癌形成过程中,垂体远侧部ACTH阳性细胞的影响。方法随机将20只3周龄SPF级断乳雄性SD大鼠分为正常对照组、实验对照组、致癌剂前补硒组、致癌剂后补硒组。用AOM(15mg/kg)每周腹腔注射,连续2周,诱导大鼠结肠癌形成。亚硒酸钠(Na2SeO3)水溶液(4mg/L)分别在AOM前、后干预,并持续至实验结束。各组均于34周后取大鼠垂体,用免疫组织化学SP法,观察垂体远侧部ACTH阳性细胞的形态结构及免疫组织化学反应强度,并进行图像分析。结果亚甲基蓝染色光镜下观察,可见AOM腹腔注射的大鼠结肠黏膜出现异常隐窝(AC)和异常隐窝灶(ACF)。免疫组织化学法显示,实验对照组大鼠垂体远侧部ACTH阳性细胞与正常对照组比较,阳性反应显著性增强(P<0.01);硒干预的各组与实验对照组相比,ACTH阳性细胞的阳性反应进一步增强(P<0.01)。结论硒可增强AOM所致大鼠结肠癌形成过程中垂体远侧部ACTH阳性细胞的功能。

THE EFFECT OF SELENIUM ON THE ACTH POSITIVE CELLS IN THE PARS DISTALIS OF PITUITARY OF RAT WITH COLON CANCER INDUCED BY AZOXYMETHANE

Objective To observe the effect of selenium on the ACTH positive cells in the pars distalis of pituitary of rat with colon mucosa cancer induced by azoxymethane(AOM).Methods Twenty 3 weeks old Sprague Dawley male rats were randomly divided into 4 groups: the normal control group;the experimental control group;the selenium before AOM induced colon mucosa cancer group;the selenium after AOM induced colon mucosa cancer group.To induce rat colon mucosa cancer,3 weeks old SD male rats received(i.p.) injections of AOM at a dose of 15mg/kg once a week for two weeks.Selenium(Na_2SeO_3,4mg/L) began to be provided in the drinking water before and after AOM administration,and lasted for the whole experiment period.The rat pituitary tissues were excised from the 34 weeks old rats.The morphological changes of the ACTH positive cells in the pars distalis of pituitary were observed using immunohistochemical methods,and then the results were analyzed by image analysis system.Results Aberrant crypt foci(ACF) and aberrant crypt(AC) were showed in the colon mucosa of rats that received two weekly i.p.injections of AOM by light microscopy with methylene blue staining.The ACTH positive cells in the experimental group rat displayed a significant increase compared with those in the normal control group rat(P<0.01) with immunohistochemical methods.There were more positive intensity in the cells with ACTH positive cells in the supplement selenium group than that in the experimental group(P<0.01).Conclusion Selenium can promote the function of the ACTH positive cells in the pars distalis of rat pituitary with colon mucosa cancer induced by AOM.