碘过量对大鼠子代神经元特异性烯醇化酶表达的影响

Experimental study on expression of neuron specific enolase in filial generation of rats by iodine excess

目的观察碘过量对大鼠子代脑神经元特异性烯醇化酶表达的影响。方法根据饮用水碘剂量的不同,将断乳后1个月Wistar大鼠随机分为5组(NI、5HI、10HI、50HI、100HI)。饲养3个月后雌雄合笼,取子一代1、20、60日龄仔鼠,测血清甲状腺激素(T3、T4),免疫组织化学染色,光镜下观察碘过量对脑神经元特异性烯醇化酶(NSE)表达的影响,图像分析不同日龄仔鼠的大脑发育情况。结果碘过量组(5HI、10HI、50HI、100HI)血清甲状腺激素水平在生后1日和20日龄时与对照组(NI)比较无明显差别在60日龄,各碘过量组甲状腺激素呈下降趋势,100HI组[T4=(37.52±8.69)nmol/L、T3=(0.61±0.16)nmol/L]与NI组[T4=(59.42±17.56)nmol/L、T3=(1.13±0.34)nmol/L]比较,差异有统计学意义(t=4.38、5.44,P<0.01)。NSE的免疫组化和形态计量学显示:海马CA3区NSE阳性细胞的数密度(NA)、体密度(VV)和灰度值随碘过量的严重程度而下降,100HI组[NA=(30.38±2.49)/mm2、VV=(0.100±0.012)、灰度值=(139.81±11.11)]与NI组[NA=(34.63±2.31)/mm2、VV=(0.122±0.018)、灰度值=(149.05±6.83)]比较,差异有统计学意义(t=4.54、3.86,P<0.01;t=2.62,P<0.05)。结论大鼠对碘摄入量的增加有较强的耐受性,在100HI组可以观察到以NSE表达降低为主要特点的脑发育障碍,其发病机理与碘过量所致的甲状腺功能低下有关。

Objective To observe the effects of iodine excess on expression of neuron specific enolase（NSE）in filial generation of rats. Methods According to different iodine levels in drinking water, the Wistar rats were divided into five groups at random. （NI,5HI, 10HI,50HI, 100HI）. After being fed for three months, the rats were mated and their filial generations at the age of 1 ,20 and 60 day were observed. The serum thyroid hormones at the age of 60 day were measured. NSE expression in hippocampus of both control and iodine excess rats was observed under light microscope after immunohistochemical staining, the development of brain of rats of different days of age was studied by image -analysis. Results There were no significant changes observed in all iodine excess groups at the age of 1 day and 20 days compared with NI group. The results of serum thyroid hormones revealed a decreasing tendency in experimental groups gradually increased iodine intake, however, a significantly statistical difference （t = 4.38,5.44,P 〈 0.01） was observed in 100HI group[T4 = （37.52 ± 8.69）nmol/L, T3 = （0.61 ± 0.16）nmol/L]compared with NI group [T4 = （59.42 ±17.56）nmol/L, T3 = （1.13 ± 0.34）nmol/L] at the age of 60 days. Immunohistochemical staining and morphological image analysis of NSE positive neurons in hippocampus CA3 area indicated that numerical density on area（NA）,volume density （Vv） and the average of gray scale were gradually decreased correlated with iodine excess levels, furthermore, statistically significance（t = 4.54.3.86, P 〈 0.01; t = 2.62, P 〈 0.05） was found in 100HI group [NA = （30.38 ± 2.49）/mm^2, Vv= （0.100 ± 0.012）, gray scale = （139.81±11.11）] compared with NI group [NA= （34.63±2.31）/mm^2, Vv= （0.122±0.018）, gray scale = （149.05 ± 6.83）]. Conclusions Wistar rats have a strong tolerance to excessive iodine intake. In 100HI group at the age of 60 days, retardation of the brain development has been observed, which is characterized by decrease NSE expression. The pathogenesis may be related with hypothyroidism induced by iodine excess.