Sharif N A, Burt D R
Neurosci Lett. 1983 Aug 19;39(1):57-63. doi: 10.1016/0304-3940(83)90165-9.
Chemical properties of receptor binding sites for thyrotropin-releasing hormone (TRH) in rat pituitary, retina, amygdala and hypothalamus were compared by examining the influence of sulfhydryl reagents on specific binding of 3H-TRH ([3H]MeTRH). Dithiothreitol-induced reduction of disulfide bonds, alkylation of thiol residues by N-ethylmaleimide and their oxidation by 5,5-dithiobis(2-nitrobenzoic acid) (DTNB), all produced marked reduction of [3H]MeTRH binding, which could be prevented in part by preincubation with exogenous TRH. In all tissues, concentration-dependent loss of binding activity was observed following exposure to micromolar heavy metals and mono- and divalent cations, with apparent additive effects between cations and DTT and NEM. Most changes appeared to reflect only a decrease in receptor density (Bmax). The similar sensitivity of all tissues to these compounds complements existing evidence for a close resemblance of TRH receptors in the CNS and pituitary.
通过检测巯基试剂对³H-促甲状腺激素释放激素([³H]MeTRH)特异性结合的影响，比较了大鼠垂体、视网膜、杏仁核和下丘脑促甲状腺激素释放激素(TRH)受体结合位点的化学性质。二硫苏糖醇诱导二硫键还原、N-乙基马来酰亚胺对巯基残基的烷基化作用以及5,5-二硫代双(2-硝基苯甲酸)(DTNB)对其的氧化作用，均使[³H]MeTRH结合显著减少，预先用外源性TRH孵育可部分防止这种减少。在所有组织中，暴露于微摩尔浓度的重金属以及单价和二价阳离子后，观察到结合活性呈浓度依赖性丧失，阳离子与二硫苏糖醇和N-乙基马来酰亚胺之间存在明显的累加效应。大多数变化似乎仅反映受体密度(Bmax)降低。所有组织对这些化合物的相似敏感性补充了中枢神经系统和垂体中TRH受体密切相似的现有证据。
