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

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

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／kg）和饮水（含碘5、1845、20295μg/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25404．3μg／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6．0×10^3μg/L、10倍碘组27．1×10^3μg／L、100倍碘组191．0×10^3μg/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 mRNA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NIS 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NIS mRNA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。

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 300 Izg/L and drinking water of iodine at 5, 1845, 20 295 μg/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 spoctrophotometric method. Their mammary 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（3597.5 μg/L） and 100HI group（25 404.3 μg/L） increased obviously compared with that of NI group（344.7 μg/L）. The milk iodine of 10HI group（27.1 × 10^3 μg/L） and 100HI group（191.0 × 10^3 μg/L） was higher than that of NI group（6.0 × 10^3 μg/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. Condusions 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.