Takahashi T
Jpn J Physiol. 1987;37(2):255-65. doi: 10.2170/jjphysiol.37.255.
3,5-Dimethyl-3'-isopropyl-L-thyronine (DIMIT)-induced fetal hyperthyroid rats showed a marked accumulation of intracellular tubulin content in the cerebral cortex, hypothalamus, and cerebellum at 1 day old. When the fetuses were transplacentally radio-thyroidectomized with the administration of [131I]-Na, the brain weight was not changed at 1 day old. The DNA content was not affected by the radio-thyroidectomy (Tx), but intracellular RNA concentration (per DNA) was increased in the hypothalamus and cerebellum at that age. The DIMIT-supplement to Tx-fetuses failed to restore these abnormal values to normal. Delayed effects of the fetal Tx were observed in 11-day-old infants. These neonates showed decreased weight gain in the body, brain, cerebral cortex, and cerebellum. The DNA content (per wet tissue) was higher in the hypothalamus and cerebellum. The intracellular concentrations of RNA and tubulin (per DNA) were significantly decreased in the hypothalamus. These values were restored to normal by the administration of L-thyroxine(T4) to rats between 1 and 10 days old. These results demonstrate that fetal nervous tissues are sensitive to changes in thyroid functions. The different manner of response to the hormonal states among the brain areas may reflect that each nervous tissue has a specific critical period for thyroid hormones during development.
3,5-二甲基-3'-异丙基-L-甲状腺素（DIMIT）诱导的胎儿甲状腺功能亢进大鼠在出生1天时，大脑皮质、下丘脑和小脑中细胞内微管蛋白含量显著增加。当胎儿通过给予[131I]-Na进行经胎盘放射性甲状腺切除时，出生1天时脑重量未改变。DNA含量不受放射性甲状腺切除（Tx）的影响，但该年龄段下丘脑和小脑中细胞内RNA浓度（每DNA）增加。给Tx胎儿补充DIMIT未能将这些异常值恢复正常。在11日龄婴儿中观察到胎儿Tx的延迟效应。这些新生儿在身体、大脑、大脑皮质和小脑中体重增加减少。下丘脑和小脑中DNA含量（每湿组织）较高。下丘脑中RNA和微管蛋白的细胞内浓度（每DNA）显著降低。在1至10日龄的大鼠中给予L-甲状腺素（T4）可将这些值恢复正常。这些结果表明，胎儿神经组织对甲状腺功能变化敏感。大脑区域之间对激素状态的不同反应方式可能反映出每个神经组织在发育过程中对甲状腺激素有特定的关键期。
