大鼠脂肪细胞中的核三碘甲状腺原氨酸结合位点。

Nuclear triiodothyronine binding sites in rat adipocytes.

作者信息

Buergi U, Abbuehl U

出版信息

Metabolism. 1984 Apr;33(4):326-8. doi: 10.1016/0026-0495(84)90192-6.

Abstract

Most effects of thyroid hormones appear to be mediated by the binding of triiodothyronine (T3) to nuclear triiodothyronine binding sites (NT3BS). Although thyroid hormones influence adipocyte metabolism, NT3BS have not been described in mature adipocytes yet. This report describes T3 nuclear binding in isolated nuclei from rat epididymal fat pad adipocytes. Nuclei were isolated by exposing collagenase-dispersed adipocytes to STM (sucrose, 0.25 mol/L; TRIS, 20 mmol/L; MgCl2, 1.1 mmol/L, pH 7.85) containing 0.5% (vol/vol) Triton X-100. Incubation of nuclei suspended in STM/EDTA (2 mmol/L)/DTT (5 mmol/L) with 125I-T3 and varying concentrations of unlabeled T3 at 37 degrees C for one hour revealed the presence of high-affinity, low-capacity NT3BS. Their MBC was 0.39 +/- 0.04 (SD) ng of T3 per milligram of DNA and their Kd was 1.4 +/- 0.5 (SD) X 10(-10) mol/L T3. Specific binding reached a plateau between 30 minutes and two hours of incubation. The addition of 5 X 10(-7) mol/L T3 to nuclei incubated for one hour with 2 X 10(-11) mol/L T3 completely displaced the specifically bound 125I-T3 within 30 minutes. Thyroxine (T4) and 3, 3', 5'-triiodothyronine (rT3) could displace 125I-T3 from the NT3BS but were less than 10% and 1% as effective, respectively, as T3. Rat epididymal fat pad adipocytes contain NT3BS, the binding characteristics of which are similar to those of rat hepatic NT3BS.

摘要

甲状腺激素的大多数作用似乎是由三碘甲状腺原氨酸（T3）与核三碘甲状腺原氨酸结合位点（NT3BS）结合介导的。尽管甲状腺激素会影响脂肪细胞代谢，但成熟脂肪细胞中尚未发现NT3BS。本报告描述了从大鼠附睾脂肪垫脂肪细胞分离的细胞核中T3的核结合情况。通过将胶原酶分散的脂肪细胞暴露于含有0.5%（体积/体积） Triton X-100的STM（蔗糖，0.25 mol/L；TRIS，20 mmol/L；MgCl2，1.1 mmol/L，pH 7.85）中来分离细胞核。将悬浮于STM/EDTA（2 mmol/L）/DTT（5 mmol/L）中的细胞核与125I-T3以及不同浓度的未标记T3在37℃孵育1小时，结果显示存在高亲和力、低容量的NT3BS。其MBC为每毫克DNA 0.39±0.04（标准差）ng T3，其Kd为1.4±0.5（标准差）×10⁻¹⁰ mol/L T3。特异性结合在孵育30分钟至2小时之间达到平台期。将5×10⁻⁷ mol/L T3添加到与2×10⁻¹¹ mol/L T3孵育1小时的细胞核中，30分钟内可完全取代特异性结合的125I-T3。甲状腺素（T4）和3,3',5'-三碘甲状腺原氨酸（rT3）可从NT3BS上取代125I-T3，但它们的效力分别仅为T3的不到10%和1%。大鼠附睾脂肪垫脂肪细胞含有NT3BS，其结合特性与大鼠肝脏NT3BS相似。