膳食锌对小鼠中枢神经系统微管蛋白表达的影响

EFFECTS OF DIETARY ZINC ON α-TUBULIN AND β-UBULIN EXPRESSION IN THE CENTRAL NERVOUS SYSTEM OF MICE

目的 通过观察中枢神经系统 (CNS)中 α-微管蛋白 (α- Tub)及 β-微管蛋白 (β-Tub)的表达 ,探讨膳食锌调节 CNS微管聚合作用的可能机制。方法 80只刚怀孕 ICR母鼠随机分为严重缺锌组、轻度缺锌组、适锌组、高锌组和高锌对喂组五组 ,在孕期和哺乳期分别饲喂含 1、5、30、1 0 0和 1 0 0 mg/ kg锌水平的实验饲料 ;断奶期 (仔鼠 2 0日龄 )后各组均改喂普通饲料。取各实验组动物第 1 0天胚胎 (E1 0 )头和身体、及第 1 5天胚胎 (E1 5 )、出生第 1天 (P1 )、第 5天 (P5 )、第 1 0天(P1 0 )、第 2 0天 (P2 0 )和第 70天 (P70 ,成年 )大脑、小脑和肝组织 ,采用 Western blot技术检测其 α-Tub和 β- Tub表达情况。结果 实验仔鼠从胚胎早期 (E1 0 )至发育成熟 (P70 ) CNS中均有微管蛋白 (Tub)表达 ,而肝组织中未见有 Tub印迹出现 ;α- Tub和 β- Tub在大脑和小脑的表达模式相似 ,即发育早期有上调趋势 ,达到表达高峰 (P5～P1 0 )后表达量逐步下调 ,α- Tub在 P5达到表达高峰 ,而β- Tub在 P1 0达到表达高峰 ;比较实验组各期 Tub表达水平 ,依次为 1 mg/ kg组 <5 mg/ kg组<30 mg/ kg组 <1 0 0 mg/ kg组 ,大脑和小脑 α- Tub、β- Tub水平与膳食锌水平具有明显的依赖关系。结论 发育期锌缺乏可抑制 CNS中 α-

Objective: To determine the effects of zinc deficiency on microtubules polymerization and the expression of α tubulin and β tubulin subunits in the central nervous system (CNS) of mice. Methods: Maternal ICR mice were fed experimental diets containing different levels of zinc (1 mg, 5mg, 30 mg and 100 mg zinc per kg diet) during pregnancy and lactation respectively. From weaning period (post day 20) to postnatal day 70 (P70), all experimental offsprings were fed normal diets. The α tubulin and β tubulin subunits expression in heads and bodies at embryonic day 10 (E10), in cerebrum, cerebellum and liver at embryonic day 15 (E15), postnatal day 1 (P1), postnatal day 5 (P5), postnatal day 10 (P10), postnatal day 20 (P20) and P70 were examined by Western blot assays. Results: The results showed that α tubulin and β tubulin subunits were expressed in neural tube (E10), cerebrum and cerebellum from early embryonic stage (E10) to adult (P70). No α tubulin and β tubulin subunits were found in livers. The patterns of α tubulin and β tubulin expressions in cerebrum and cerebellum were similar in that its expression was up regulated at early development stage. After the expressions of α tubulin and β tubulin subunits arrived the expression peaks (α tubulin at P5 and β tubulin at P10), they began to down regulate. There was a close relationship between the concentration of dietary zinc and the level of α tubulin and β tubulin subunits expressions. The order of expression levels was 1 mg/kg group<5 mg/kg group<30 mg/kg group<100 mg/kg group. Conclusion: Zinc deficiency in developing period can inhibit the expression of tubulin subunits, and zinc supplementation can improve its expression. The decline of tubulin subunits expression is one of important mechanisms for microtubules polymerization impairments resulting from zinc deficiency.