锌对缺碘受孕大鼠和仔鼠甲状腺功能及脑发育影响的实验研究

Experimental study of zinc on the function of thyroid and brain development in iodine deficiency pregnant and filial rats

目的观察锌对碘缺乏妊娠大鼠及仔鼠生长发育、甲状腺和脑形态与功能及相关激素的影响。方法用低碘饲料喂养Wistar雌性大鼠，同时设补碘、补复合锌、补葡萄糖酸锌、补碘加复合锌组。第90天时将动物模型进行交配，于第21天处死孕鼠，查活胎体质量、畸胎、死胎率和胚胎吸收率，对垂体、甲状腺称质量，测血清甲状腺激素、促性腺激素和性激素水平。各组仔鼠于生后第45天对垂体、甲状腺称质量，测脑组织蛋白质、DNA、RNA水平。结果缺碘组孕鼠尿碘低下，甲状腺肿大，T4、FT4降低（P〈0．01），T3、FT3升高（P〈0．01）；促性腺激素和性激素异常；胎鼠体质量降低，死胎、吸收胎增加；仔鼠体质量增长缓慢，甲状腺肿大，脑质量减轻，蛋白质、DNA、RNA水平减低，同时RNA／DNA和蛋白质／DNA比值降低（P〈0．01）。补锌组孕鼠甲状腺质量较缺碘组减轻（P〈0.01），甲状腺激素、促性腺激素和性激素部分恢复；胎鼠体质量增加，死胎和胚胎吸收率降低；仔鼠甲状腺肿大减轻，体质量增加，脑蛋白质、DNA、RNA水平和RNA／DNA、蛋白质／DNA比值升高（P〈0．01）。结论缺碘大鼠补锌降低甲状腺肿大程度；调节甲状腺激素、促性腺激素和性激素代谢紊乱；其生育的仔鼠甲状腺肿大减轻，大脑蛋白质、DNA、RNA水平增加。由此认为，补锌拮抗由缺碘所致的孕鼠生殖和胎鼠发育异常及仔鼠脑发育障碍。

Objective To observe the effects of zinc （Zn） on growth, thyroid and brain morphology and function and the related hormones in iodine deficiency （ID） pregnant rats and neonates born to ID rats. Methods Wistar female rats were randomly divided into normal control group and 5 ID groups fed with forage from ID areas. Except for the group of ID control, iodine （I）, compound zinc （ZnC）, I ＋ ZnC, zinc gluconate （ZnG） were given to other 4 ID. 90 days after, the female rats were mated with male rats. All the pregnant rats were killed on the D21 of pregnancy. The body weight, the number and rate of fetus absorption, the death and malformation in fetus were determined. The weight of thyroid and pituitary were observed and the levels of thyroid hormone, gonadotropin, and sex hormones in the serum were tested. In the experimental study of filial rats, the weight of thyroid and pituitary were observed and the contents of protein, DNA and RNA were measured when they were 45 days old. Results Pregnant rats in ID group developed goiter, had a decrease in urine iodine, T4 and FT4, and an increase in T3 and FT3 （P 〈 0.01）. Their gonadotropic and sexual hormones were abnormal. The weight gain of pregnant rats was decreased. The rate of malformation, dead and absorbed fetuses were increased. While filial rats with iodine deficiency had goiter and less weight gain. They also had decreased content of the protein, DNA and RNA in the brain, the rate of RNA/DNA and Pr/DNA（P 〈 0.01 ）. After Zn administration, the weight of thyroid of the pregnant rats Were lowered （P 〈 0.01 ） and the thyroid hormone, gonadotropic and sexual hormones were restored to some degree. The weight of fetus was increased and the malformation, dead and absorbed fetus were decreased. At the same time, filial rats gained body weight, had a decrease of the weight of thyroid, an increase of the content of the protein. DNA and RNA in the brain and the rate of RNA/DNA and Pr/DNA elevated after Zn administration （P 〈0.01 ）. Conclusions Zn supplementation could decrease the degree of goiter, reduce the disorder of thyroid hormone, gonadotropic and sexual hormones and raise the content of the protein, DNA and RNA, thus antagonize genetic abnormality in pregnant rats, the anomaly of fetus growth and the obstacle of brain growth in filial rats caused by ID.