雌二醇对甲基亚硝基脲诱发鼠乳腺癌的抑制作用

Inhibitory effect of pretreatment with 17 β-estradiol on mammary cancinomas induced by N-methyl-N-nitrosourea in F344 rats

目的:研究雌二醇（E2）及催乳素对甲基亚硝基脲（MNU）诱发鼠乳腺癌（MCAs）的影响。方法:给7周雌性F344鼠单次iv MNU 50mg/kg,同时给予2.5 mg E2或通过移植MtT/F84持续供应催乳素或生长激素。在iv MNU后,对小鼠进行为期36周的观察。结果:与单独用MNU相比,合用MNU和E2对MCAs的发生影响不大;而在MNU之前用2.5mgE2连续2周治疗小鼠,则能有效降低MCAs的发生。相反,MNU和MtT/F84合用的MCAs发生率高且潜伏期短。与单独用MNU相比,E2治疗组的平均垂体重量和血清催乳素水平明显上升,平均E2水平93ng/ml,而非E2治疗组只有0.06ng/ml;MtT/F84组的血清催乳素水平也明显提高。结论:在MNU之前经E2预处理,可明显抑制MNU诱发F344鼠MCAs的发生。

Objective: To investigate the influence of 17 (3-estradiol (E2) and prolactin on N-methyl-N-nitrosourea (MNU)-induced mammary carcinomas (MCAs) in rats. Methods: MNU was intravenously injected once into 7-week-old female F344 rats at a dose of 50 mg/kg body weight. Groups of rats also received either 2. 5 mg of E2 or a continuous supply of prolactin and/or growth hormone via transplanted MtT/F84 (mammo-somatotropic pituitary tumor). Rats were observed for up to 36 weeks after MNU administration. Results: Although simultaneous administration of MNU and E2 did not much affect the occurrence of MCAs as compared with administration of MNU alone, rats treated with 2. 5 mg of E2 for 2 weeks before MNU administration significantly reduced occurrence of MCAs as compared with those given MNU alone. In contrast, rats receiving MNU plus MtT/F84 showed high incidence and shortened latency of MCAs. Average pituitary weight and serum prolactin levels in E2-treated rats were greatly increased as compared with those receiving MNU-alone. Average serum E2 level was 93 ng/ml in E2-treated group. Serum prolactin levels were greatly increased in rats receiving MtT/F84. Conclusion: Pretreatment with E2 before MNU administration can inhibit the occurrence of MCAs induced by MNU in female F344 rats.