不同饲料锌水平对哺乳期后幼鼠大脑及睾丸组织ZnT3mRNA表达的影响

Effects of different zinc intakes on brain and testis expression of zinc transporter 3 mRNA in weaned mice

目的:观察哺乳期后幼鼠在不同饲料锌水平条件下的生长情况,探讨饲料中锌水平对幼鼠大脑皮质、海及睾丸组织锌转运体3(ZnT3)mRNA表达的影响。方法:20只雄性3周龄ICR幼鼠(P21)随机分为饲料缺锌(ZD,Zn 1 mg／kg)、适锌(ZA,Zn 30 mg／kg)、高锌(ZS,Zn 180 mg／kg)、高锌对喂(PF,Zn 180 mg／kg,每目饲料投放量依据缺锌组每日摄食量确定)4组,以相应饲料饲喂3周(P21-P42),观察小鼠P21-P42期间的摄食量及体质量变化。饲喂3周后,处死小鼠取血清及大脑皮质、海马、睾丸组织,以原子吸收分光光庋法测定小鼠血清锌含量,半定量RT-PCR法检测分析不同饲料锌水平幼鼠P42时相应组织中ZnT3 mRNA的表达。结果:断乳幼鼠饲喂不同水平锌饲料3周后,ZD组幼鼠摄食量及体质量显著低于其余各组(P<0.05,P<0.01),血清锌也显著低于其余各组(P<0.05,P<0.01)。P42时ZD小鼠睾丸及皮质中ZnT3 mRNA表达显著降低(p<0.05),PF小鼠海马中ZnT3 mRNA表达高于其他各组(P<0.05)。结论:哺乳期后保证饲料中足量锌对幼鼠的生长发育十分重要;饲料缺锌显著降低哺乳期后小鼠睾丸及皮质ZnT3 mRNA表达,这种基因表达变化可能是哺乳期后幼鼠维持锌内稳态的一种反馈保护机制。

Objective:To observe the growth and development of the weaned mice fed with different levels of dietary zinc and to explore the expression of zinc transporter 3(ZnT3) mRNA induced by different dietary zinc intakes. Methods: Twenty male weaned mice (postnatal day 21) were divided into 4 groups: zinc deficient (ZD), zinc adequate(ZA), zinc supplemental (ZS) and pair fed(PF). Mice were fed with different levels of dietary zinc for 3 weeks (from postnatal day 21 to postnatal day 42) ;the zinc contents of ZD, ZA, ZS and PF group were 1 mg/kg, 30 mg/kg, 180 mg/kg and 180 mg/kg respectively. From postnatal day 21 to postnatal day 42, the diet intakes and weight of the mice were measured everyday. On postnatal day 42, the mice were sacrificed and tissues were immediately isolated and frozen lor RNA extraction. The serum zinc concentrations were measured by AAS and the expression of ZnT3 mRNA was determined by semiquantitative RT-PCR. Results: The dietary intakes and weight of ZD mice were much lower than that of other groups(P3<0. 05,P<0. 01). Serum zinc concentration of ZD group also declined significantly compared with other groups(P<0. 05,P<0. 01). ZnT3 mRNA expressions in testis and cerebral cortex were depressed(P<0. 05,P<0. 01) following dietary zinc deficiency, but the ZnT3 mRNA expression in hippocampus in PF group was higher than those in other groups(P<0. 05). Conclusion: The results suggest that adequate dietary zinc is very important for growth and development of weaned mice. Dietary zinc deficiency causes significant decline of ZnT3 mRNA expression in testis and cerebral cortex in mice, which may be a protective mechanism for cellular zinc homeostasis.