碘过量对哺乳期母鼠乳腺钠碘转运体mRNA和蛋白表达的影响

目的 观察碘过量对哺乳期母鼠乳腺钠碘转运体(sodium-iodide symporter,NIS)mRNA及蛋白表达的影响.方法 断乳1个月健康Wistar大鼠60只,雌雄比为2:1.将大鼠按体质量随机分为适碘组(30只)、10倍碘组(15只)、100倍碘组(15只),通过饮食(含碘300μg/ks)和饮水(含碘5、1845、20 295μg/L)摄碘.喂养3个月后交配产仔鼠,在哺乳第10天,采用砷铈催化分光光度法测定母鼠尿碘和乳汁碘.取母鼠乳腺,用反转录聚合酶链反应(RT-PCR)测定NIS mRNA表达;用SABC法进行免疫组化染色观察NIS蛋白表达强度.结果 ①母鼠尿碘:适碘组344.7μg/L、10倍碘组3597.5μg/L、100倍碘组25 404.3μg/L,10倍碘组和100倍碘组分别是适碘组的10.4倍和73.7倍.②母鼠乳汁碘:适碘组6.0×103μg/L、10倍碘组27.1×103μg/L、100倍碘组191.0×103μg/L,10倍碘组和100倍碘组分别是适碘组的4.5倍和31.8倍,母鼠乳汁碘增加倍数低于尿碘.③母鼠乳腺NIS表达:NIS raRNA表达组间比较差异有统计学意义(F=24.19,P＜0.01);其中适碘组(1.532±0.044)较10倍碘组(1.250±0.034)、100倍碘组(1.272±0.039)明显增高(P＜0.01),而且哺乳期母鼠乳腺N1S mRNA表达(1.532±0.044)高于非哺乳期母鼠(0.879±0.018),二者比较差异有统计学意义(t=19.09,P＜0.01);母鼠乳腺NIS蛋白表达强度随碘摄入量增加而减弱.结论 过量碘摄入可抑制乳腺NISmRNA和蛋白表达,限制乳汁中的含碘量随碘摄入量增加的幅度,此机制对下一代有着重要的保护作用.

Effect of excessive iodine intake on sodium-iodide symporter mRNA and protein expression of breast in lactating rats

Objective To study effect of excessive iodine intake on sodium-iodide symporter(NIS)mRNA and protein expression of breast in lactating rats.Methods 60 Wistar rats,having been weaned for one month,were randomly divided into three groups according to their body weights,I.e,①normal iodine(NI,30 rats);②ten fold high iodine(10 HI,15 rats);③one hundred fold high iodine(100 HI,15 rats).Eating food containing iodine of 300μg/L and drinking water of iodine at 5,1845,20 295μg/L,respectively.After fed for 3 months,the rats mated and had offspring,and urine and milk iodine of lactating rats were determined by As-Ce-catalytic spectrophotometric method.Their marmnary glands were sampled at lactation day 10.Then NIS mRNA expression by RT-PCR was determined and NIS protein by immunohistochemistry(SABC)was observed.Results The urine iodine of 10 HI group(3597.5μg/L)and 100HI group(25 404.3μg/L)increased obviously compared with that of NI group(344.7μg/L).The milk iodine of 10HI group(27.1×103μg/L)and 100HI group(191.0×1μg/L)was higher than that of NI group(6.0×103μg/L),but the increased fold of milk iodine was not paralleled with that of urine iodine.Difference of NIS mRNA expression was significant(F=24.19,P＜0.01)among the groups,and the NIS mRNA expression in 10HI(1.250±0.034)and 100HI(1.272±0.039)group were less than that in NI (1.532±0.044)group(P＜0.01).The breast NIS mRNA expression in lactating rats(1.532±0.044)was significantly higher than that in unlactating rats(0.879±0.018,P＜0.01).With the increasing iodine uptake,NIS protein expression decreased.Conclusions The NIS mRNA and protein in rat breasts is down-regulated by excessive iodine intake.So increasing extent of milk iodine concentration is inhibited,which is important to prevent off-spring from getting excessive iodine intake from parental generation.