Bournaud F, Gourdji D, Mongongu S, Tixier-Vidal A
Neuroendocrinology. 1977;24(3-4):183-94. doi: 10.1159/000122760.
[3H]Thyroliberin (TRH) has been previously shown to enter its target GH3 cells. Intracellular [3H]-TRH was found chemically unmodified and associated to organites, cytosol and nucleus. We studied the [3H]-TRH binding capacity of a highly purified nuclear fraction isolated by an original procedure from GH3 cells. The nuclei still presented their double nuclear envelope. They are able to bind [H]-TRH to the same extent as nuclei isolated from GH3 cells previously exposed to [3H]-TRH. The equilibrium of binding was reached after 2--5 min incubation at 25 degrees or 35 degrees C. The binding is stable at 4 degrees C and partially (50%) dissociated within 15 min at 25 degrees C. 50% of the binding was inhibited by large excess of unlabelled TRH. Nuclei obtained from a variant GH3 cell which has lost its responsiveness to TRH presented only the noncompetitive binding compartment. The binding was found dose dependent and not saturable. Two apparent dissociation constants were evaluated: 1.5--2.5 x 10--8M and 2.10--6M, respectively, for high and low doses of [3H]-TRH. The first one was identical to that previously found for intact GH3 cells. The present data show the existence of specific nuclear binding sites for TRH, establish their characteristics and suggest a possible nuclear site of action for that peptide hormone.
[3H]促甲状腺素释放激素（TRH）先前已被证明可进入其靶细胞GH3。细胞内的[3H]-TRH在化学上未被修饰，并与细胞器、胞质溶胶和细胞核相关联。我们研究了通过一种从GH3细胞中分离高纯度核组分的原始方法所得到的该组分对[3H]-TRH的结合能力。这些细胞核仍然呈现出它们的双层核膜。它们结合[H]-TRH的程度与从先前暴露于[3H]-TRH的GH3细胞中分离出的细胞核相同。在25℃或35℃孵育2 - 5分钟后达到结合平衡。该结合在4℃时稳定，在25℃时15分钟内部分（50%）解离。大量未标记的TRH可抑制50%的结合。从对TRH失去反应性的变异GH3细胞中获得的细胞核仅呈现非竞争性结合区室。发现该结合呈剂量依赖性且不饱和。评估了两个表观解离常数：对于高剂量和低剂量的[3H]-TRH，分别为1.5 - 2.5×10⁻⁸M和2.10⁻⁶M。第一个与先前在完整GH3细胞中发现的相同。目前的数据表明存在TRH的特异性核结合位点，确定了它们的特征，并提示了该肽类激素可能的核作用位点。
