Taylor R L, Burt D R
Neuroendocrinology. 1981 May;32(5):310-6. doi: 10.1159/000123177.
[3H]-3-methyl-His2]thyrotropin releasing hormone ([3H]MeTRH) binds to sites in the sheep anterior pituitary gland which appear to be the same as those occupied by [3H]TRH and which can therefore be identified as TRH receptors. In competition experiments performed in parallel, both ligands gave the same number of binding sites, 15 pmol/g wet weight, and showed the same pharmacology for 19 TRH analogs ranging over more than 5 orders of magnitude in potency. The apparent dissociation constant of binding of [3H]MeTRH was about 3.5 nM compared to 29 nM for [3H]TRH. Kinetic experiments with [3H]MeTRH yielded a rate constant for association of 1.4 x 10(7) M-1 min-1 and rate constants for the biphasic dissociation of 5 x 10(-2) min-1 (fast phase) and 7 x 10(-3) min-1 (slow phase). Detailed methods are described for preparation of [3H]MeTRH by reduction of the dehydroproline precursor and its purification by ion exchange and antibody affinity chromatography. The major advantage of the new ligand is that its higher affinity of binding gives relatively less non-specific binding than is obtained with [3H]TRH, particularly in central nervous tissue.
[3H]-3-甲基组氨酸2]促甲状腺激素释放激素（[3H]MeTRH）与绵羊垂体前叶中的位点结合，这些位点似乎与[3H]TRH所占据的位点相同，因此可被鉴定为TRH受体。在平行进行的竞争实验中，两种配体给出的结合位点数相同，为15 pmol/g湿重，并且对19种TRH类似物表现出相同的药理学特性，其效力范围超过5个数量级。[3H]MeTRH结合的表观解离常数约为3.5 nM，而[3H]TRH为29 nM。用[3H]MeTRH进行的动力学实验得出缔合速率常数为1.4×10(7) M-1 min-1，双相解离的速率常数分别为5×10(-2) min-1（快相）和7×10(-3) min-1（慢相）。详细描述了通过还原脱氢脯氨酸前体来制备[3H]MeTRH及其通过离子交换和抗体亲和色谱法进行纯化的方法。新配体的主要优点是其较高的结合亲和力，与[3H]TRH相比，产生的非特异性结合相对较少，尤其是在中枢神经组织中。
