Rodriguez M, Rodriguez F, Jolin T
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Endocrinology. 1992 Oct;131(4):1612-8. doi: 10.1210/endo.131.4.1396306.
The present study was undertaken to test the effect of food restriction, fasting, and diabetes on the relationship between thyroid hormone receptor occupancy and two biological end points, GH production and the inhibition of TSH secretion, in thyroidectomized rats. The estimated maximal binding capacity (MBC) in diabetic (D) and fasting (F) rats and in animals limited to 25% (FR25) of the food consumption of normal (C) rats was decreased to 57%, 73%, and 76%, respectively, of C values (P < 0.01-0.001), whereas normal values were found in thyroidectomized (Tx) rats and in animals limited to 50% (FR50) of the food intake of C animals. The nuclear T3 content and T3 receptor occupancy were reduced, respectively, to 25% and 29% in Tx, 77% and 81% in FR50, 52% and 69% in FR25, 49% and 66% in F, and 36% and 64% in D rats of the corresponding C values (P < 0.05-0.001). Pituitaries from Tx, FR50, FR25, F, and D rats contained less GH than C pituitaries (0.14%, 81%, 69%, 88%, and 51%, respectively, of C pituitaries; P < 0.05-0.001). Plasma TSH was lower in FR50, FR25, F, and D rats than in C animals (78%, 57%, 52%, and 48%, respectively (P < 0.01-0.001)), and markedly increased in Tx animals. Administration of a single dose of 2, 5, or 10 micrograms T3/100 g BW to Tx C, Tx FR50, TX FR25, Tx F, and Tx D rats resulted in a similar and progressive increase in nuclear T3 in all groups, except for lower values in Tx D animals. However, receptor occupancy did not differ among the different groups at each T3 dose. This treatment resulted in a progressive increase in pituitary GH in all groups; however, in Tx FR50, Tx FR25, Tx F, and Tx D pituitaries, the GH responses to 10 micrograms T3 were only 77%, 59%, 44%, and 27%, respectively, of that in Tx C rats. (P < 0.05-0.001). Moreover, significant differences in the GH response to 10 micrograms T3 were observed among Tx FR50, Tx FR25, Tx F, and Tx D animals (P < 0.01-0.001). In addition plasma TSH levels in untreated Tx FR50, Tx FR25, Tx F, and Tx D rats were only 88%, 82%, 79%, and 72%, respectively, of that in Tx C animals (P < 0.05-0.01).(ABSTRACT TRUNCATED AT 400 WORDS)
本研究旨在检测食物限制、禁食和糖尿病对甲状腺切除大鼠甲状腺激素受体占有率与两个生物学终点（生长激素（GH）分泌及促甲状腺激素（TSH）分泌抑制）之间关系的影响。糖尿病（D）大鼠、禁食（F）大鼠以及食物摄入量限制为正常（C）大鼠25%（FR25）的动物，其估计最大结合能力（MBC）分别降至C组值的57%、73%和76%（P<0.01 - 0.001），而甲状腺切除（Tx）大鼠以及食物摄入量限制为C组动物50%（FR50）的动物MBC值正常。Tx大鼠、FR50大鼠、FR25大鼠、F大鼠和D大鼠的细胞核三碘甲状腺原氨酸（T3）含量及T3受体占有率分别降至相应C组值的25%和29%、77%和81%、52%和69%、49%和66%、36%和64%（P<0.05 - 0.001）。Tx大鼠、FR50大鼠、FR25大鼠、F大鼠和D大鼠垂体中的GH含量低于C组垂体（分别为C组垂体的0.14%、81%、69%、88%和51%；P<0.05 - 0.001）。FR50大鼠、FR25大鼠、F大鼠和D大鼠的血浆TSH低于C组动物（分别为78%、57%、52%和48%，P<0.01 - 0.001），而Tx动物的血浆TSH显著升高。给Tx C大鼠、Tx FR50大鼠、Tx FR25大鼠、Tx F大鼠和Tx D大鼠单次注射2、5或10微克T3/100克体重，除Tx D动物数值较低外，所有组的细胞核T3均有相似且逐步的增加。然而，在每个T3剂量下，不同组之间的受体占有率并无差异。该处理使所有组垂体GH逐步增加；然而，在Tx FR50大鼠、Tx FR25大鼠、Tx F大鼠和Tx D大鼠垂体中，对10微克T3的GH反应分别仅为Tx C大鼠的77%、59%、44%和27%（P<0.05 - 0.001）。此外，在Tx FR50大鼠、Tx FR25大鼠、Tx F大鼠和Tx D大鼠之间观察到对10微克T3的GH反应存在显著差异（P<0.01 - 0.001）。另外，未处理的Tx FR50大鼠、Tx FR25大鼠、Tx F大鼠和Tx D大鼠的血浆TSH水平分别仅为Tx C动物的88%、82%、79%和72%（P<0.05 - 0.01）。（摘要截短至400字）
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