| For realizing the impact on brain development of iodine excess, expressions of type 2, type 3 iodothyronine deiodinase (D2, D3) were detected in vivo and in vitro tests. Based on the successful establishment of animal model of iodine deficiency and iodine excess, the changes of iodothyronine deiodinases mRNA in cerebrum, cerebella and hippocampus of different iodine intake animal have been observed. In vitro, 100nM T3 or 100nM T4 acted on the cultured neural cell at different time. The impact of TH on D2mRNA and D3mRNA has been observed by semi-quantity RT-PCR. The survival of neural cell in iodine excess has been revealed by MTT.In vivo study, 1 month Wistar rats were divided into six groups randomly base on sex and weight. Rats of LI (low iodine intake) group were given low iodine diet and deionized water. Animals in NI (normal iodine intake) group were fed with normal iodine diet and tap water. In HI (high iodine intake) group, 5 times, 10 times, 50times and 100 times iodine respectively added into tap water, and then gave different animals. And these rats in HI group were also fed with normal iodine diet. After 3 months, 10 rats in each group were sacrificed. The following indicators were measured: urinary iodine, serum TT3 TT4 FT3 FT4 rT3, activities of D2 in brain, D2mRNA and D3mRNA in cerebrum, cerebella, and hippocampus. And 6 months later, the same test was also completed. The results showed: (1) The relativity of iodine intake and urinary iodine wasexcellent. Animal model was successful. (2) In 3 months later study, serum TT4 FT4 of LI group was significantly lower than that of NI group and serum TT3 FT3 was stable. The quantity of rT3 was markedly lesser than normal level. D2 activity was significantly higher in LI group than that of other groups. D2mRNA had no significant difference among groups. D3mRNA was so little that can't be detected. (3) Serum TT3 TT4 FT3 FT4 rT3 in HI groups had a decreasing tendency. Serum FT3 in 10HI, 50HI and 100HI groups were all significantly lower than that of NI group. In 100HI group, five thyroid hormones in serum all decreased markedly. D2 activity had a decreasing tendency too in HI groups. D2mRNA kept a steady level. D3mRNA increased in some animals of HI groups. (4) In 6 months later study, serum thyroid hormones in LI group decreased evidently. Rats in HI groups showed hypothyroidism symptoms. D2 activity decreased markedly in LI group and HI groups. D2mRNA had no difference among groups. D3mRNA also increased in some animals of HI groups.In vitro study, the Wistar rat fetal cerebral hemispheres at 15-18 days of gestation were dissected, dissociated, and planted into DMEM/F12 growth medium. The cell types were identified by immunocytochemistry method. This study included two parts. One part was to observe D2mRNA and D3mRNA in cultured neural cell after treatment of T3, T4 or dexamethasone (Dex). After 12 days cultured, neural cells were divided into T3 treatment group, T4 treatment group, Dex treatment group and control group. Respectively after 1, 2, 4 and 6 hours collected neural cells of four groups for semi-quantity RT-PCR. The other part was to observe the survival of neural cell in different concentration of iodine excess. Different concentrations of KI or KIO3 were added into neural cell, detected MTT 3 days, 7 days and 10 days later respectively. The results showed: (1) Neuron and astrocyte were...
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