Abreu P, Sugden D
Biomedical Science Division, King's College London, Kensington, U.K.
Biochem Biophys Res Commun. 1990 Sep 14;171(2):875-81. doi: 10.1016/0006-291x(90)91227-j.
Specific binding sites for [3H]-1,3 di-ortho-tolylguanidine ([3H]-DTG), a selective radiolabeled sigma receptor ligand, were detected and characterized in sheep pineal gland membranes. The binding of [3H]-DTG to sheep pineal membranes was rapid and reversible with a rate constant for association (K+1) at 25 degrees C of 0.0052 nM-1.min-1 and rate constant for dissociation (K-1) 0.0515 min-1, giving a Kd (K-1/K+1) of 9.9 nM. Saturation studies demonstrated that [3H]-DTG binds to a single class of sites with an affinity constant (Kd) of 27 +/- 3.4 nM, and a total binding capacity (Bmax) of 1.39 +/- 0.03 pmol/mg protein. Competition experiments showed that the relative order of potency of compounds for inhibition of [3H]-DTG binding to sheep pineal membranes was as follows: trifluoperazine = DTG greater than haloperidol greater than pentazocine greater than (+)-3-PPP greater than (+/-)SKF 10,047. Some steroids (testosterone, progesterone, deoxycorticosterone) previously reported to bind to the sigma site in brain membranes were very weak inhibitors of [3H]-DTG binding in the present study. The results indicate that [3H]-DTG binding sites having the characteristics of sigma receptors are present in sheep pineal gland. The physiological importance of these sites in regulating the synthesis of the pineal hormone melatonin awaits further study.
在绵羊松果体膜中检测并鉴定了[3H]-1,3-二邻甲苯基胍（[3H]-DTG，一种选择性放射性标记的σ受体配体）的特异性结合位点。[3H]-DTG与绵羊松果体膜的结合迅速且可逆，在25℃时的结合速率常数（K+1）为0.0052 nM-1·min-1，解离速率常数（K-1）为0.0515 min-1，解离常数（Kd，K-1/K+1）为9.9 nM。饱和研究表明，[3H]-DTG与一类位点结合，其亲和常数（Kd）为27±3.4 nM，总结合容量（Bmax）为1.39±0.03 pmol/mg蛋白质。竞争实验表明，化合物抑制[3H]-DTG与绵羊松果体膜结合的效力相对顺序如下：三氟拉嗪 = DTG＞氟哌啶醇＞喷他佐辛＞（+）-3-PPP＞（±）SKF 10,047。一些先前报道可与脑膜中的σ位点结合的类固醇（睾酮、孕酮、脱氧皮质酮）在本研究中是[3H]-DTG结合的非常弱的抑制剂。结果表明，具有σ受体特征的[3H]-DTG结合位点存在于绵羊松果体中。这些位点在调节松果体激素褪黑素合成中的生理重要性有待进一步研究。
