Cho Young-Man, Imai Toshio, Hasumura Mai, Hirose Masao
Division of Pathology, National Institute of Health Sciences, Tokyo, Japan.
Cancer Sci. 2006 Oct;97(10):1031-6. doi: 10.1111/j.1349-7006.2006.00303.x.
Epidemiologic and experimental studies suggest that iodine deficiency increases the risk of mammary as well as thyroid cancers, but susceptibility to tumor development when this occurs during the prepubertal stage is not completely understood. In the present study, we therefore evaluated this question in F344 rats. Dams during the lactation period and their weaned offspring until postnatal week 7 were fed an iodine-free diet. Female offspring were then given 7,12-dimethylbenz[a]anthracene (DMBA, 50 mg/kg body weight) by gavage for mammary tumor induction in week 7. Both the male and female rats were given free access to drinking water containing N-bis(2-hydroxypropyl)nitrosamine (DHPN), (0.1 and 0.2% for male and female rats, respectively) for wide spectrum tumor induction in organs, including the thyroid gland, from weeks 7-11. All offspring were killed at week 50 for histopathological examination. The iodine deficiency had no significant influence on incidences and/or multiplicities of mammary and thyroid tumors. Furthermore, tumor induction in the liver, kidney, lung, esophagus and urinary bladder was not affected in either sex. The present results thus indicate a lack of influence of iodine deficiency condition early in life on subsequent carcinogenic susceptibility.
流行病学和实验研究表明，碘缺乏会增加患乳腺癌和甲状腺癌的风险，但对于青春期前阶段发生碘缺乏时肿瘤发生的易感性尚未完全了解。因此，在本研究中，我们在F344大鼠中评估了这个问题。哺乳期的母鼠及其断奶后直至出生后第7周的后代喂食无碘饮食。然后在第7周通过灌胃给雌性后代给予7,12-二甲基苯并[a]蒽（DMBA，50mg/kg体重）以诱导乳腺肿瘤。从第7至11周，雄性和雌性大鼠均可自由饮用含有N-双（2-羟丙基）亚硝胺（DHPN）的水（雄性和雌性大鼠分别为0.1%和0.2%），以诱导包括甲状腺在内的多个器官发生肿瘤。所有后代在第50周处死进行组织病理学检查。碘缺乏对乳腺和甲状腺肿瘤的发生率和/或多发性没有显著影响。此外，肝脏、肾脏、肺、食管和膀胱的肿瘤诱导在两性中均未受影响。因此，目前的结果表明生命早期的碘缺乏状况对随后的致癌易感性没有影响。
