Frankel S, Lange G
Am J Physiol. 1980 Sep;239(3):E223-6. doi: 10.1152/ajpendo.1980.239.3.E223.
Groups of rats 3, 4, 5, 7, and 10 wk of age were tested for their ability to respond to acute cold (4 degrees C for 30 min). Thyroid reactions were estimated from intrathyroidal colloid droplet (CD) counts, serum thyrotropin (TSH) and thyroxine (T4) levels. Normally CD counts increased to a maximum in the 5-wk-old rats were lower in the 7-wk-old, and still lower in the 10-wk-old animals. The significant finding was that exposure to cold caused a decrease in CD counts in 3-, 4-, 5-wk-old rats but an increase in mature animals. This CD decrease was apparent within 10 min in the 4- and 5-wk-old rats, Injections of TSH and thyrotropin-releasing hormone (TRH) raised CD counts in all age groups but had little effect on response to cold. TSH serum levels were higher in the 5-wk-old than in the 3- and 4-wk-old animals; cold caused a greater TSH reduction in the 5-wk-old rats than in younger groups. Serum T4 levels were approximately the same in 3-, 4-, and 5-wk-old rats; when they were exposed to cold, the level rose despite the fact that CD counts dropped. These data indicate that in rats hypothalamic-pituitary-thyroid reactions to acute cold attain the adult pattern between 5 and 7 wk after birth.
对3周龄、4周龄、5周龄、7周龄和10周龄的大鼠进行分组，测试它们对急性寒冷（4℃，持续30分钟）的反应能力。通过甲状腺内胶体滴（CD）计数、血清促甲状腺激素（TSH）和甲状腺素（T4）水平来评估甲状腺反应。正常情况下，CD计数在5周龄大鼠中增加到最大值，在7周龄时降低，在10周龄动物中更低。显著的发现是，暴露于寒冷环境会导致3周龄、4周龄、5周龄大鼠的CD计数减少，但成年动物的CD计数增加。在4周龄和5周龄大鼠中，这种CD减少在10分钟内就很明显。注射TSH和促甲状腺激素释放激素（TRH）可提高所有年龄组的CD计数，但对寒冷反应影响不大。5周龄大鼠的TSH血清水平高于3周龄和4周龄动物；寒冷导致5周龄大鼠的TSH降低幅度大于较年轻的组。3周龄、4周龄和5周龄大鼠的血清T4水平大致相同；当它们暴露于寒冷环境时，尽管CD计数下降，但T4水平仍会升高。这些数据表明，在大鼠中，下丘脑 - 垂体 - 甲状腺对急性寒冷的反应在出生后5至7周达到成年模式。
