Patterson T A, Connor M, Appleyard S M, Chavkin C
Department of Pharmacology, University of Washington, Seattle 98195.
Neurosci Lett. 1994 Oct 24;180(2):159-62. doi: 10.1016/0304-3940(94)90511-8.
In preparation for expression studies for rat brain sigma-binding sites, Xenopus oocytes were tested for the presence of [3H]di-o-tolylguanidine (DTG)-binding sites. Native oocytes were found to contain two intrinsic [3H]DTG-binding sites, a high-affinity site (Kd = 32 +/- 6 nM, Bmax of 45.7 +/- 19 pmol/mg protein) and a low-affinity binding site (Kd = 1.3 +/- 0.7 microM, Bmax of 3.2 +/- 0.7 nmol/mg protein). In a series of radioligand-binding-displacement studies, the high-affinity binding sites were found to have a binding profile which has a similar Kd to that of the mammalian sigma 2-binding site (32 vs. 38 nM). Comparison of the IC50 values for inhibition of [3H]DTG binding in rat liver and oocytes for DTG, haloperidol (HAL), (-)-pentazocine, (+)-3-(3-hydroxyphenyl)-N-propylpiperidine hydrochloride ((+)-3-PPP), (+)-pentazocine and Zn2+, showed similarity in rank (r2 = 0.913) but a 7-fold lower potency in oocytes. These results suggest that the high-affinity [3H]DTG-binding site in oocytes represents a sigma 2-like binding site.
为了准备大鼠脑σ结合位点的表达研究，检测了非洲爪蟾卵母细胞中[3H]二邻甲苯基胍（DTG）结合位点的存在情况。发现天然卵母细胞含有两个内在的[3H]DTG结合位点，一个高亲和力位点（Kd = 32±6 nM，Bmax为45.7±19 pmol/mg蛋白质）和一个低亲和力结合位点（Kd = 1.3±0.7 μM，Bmax为3.2±0.7 nmol/mg蛋白质）。在一系列放射性配体结合置换研究中，发现高亲和力结合位点的结合谱与哺乳动物σ2结合位点的Kd相似（32对38 nM）。比较大鼠肝脏和卵母细胞中DTG、氟哌啶醇（HAL）、（-）-喷他佐辛、（+）-3-（3-羟基苯基）-N-丙基哌啶盐酸盐（（+）-3-PPP）、（+）-喷他佐辛和Zn2+对[3H]DTG结合的抑制IC50值，发现排名相似（r2 = 0.913），但卵母细胞中的效力低7倍。这些结果表明，卵母细胞中的高亲和力[3H]DTG结合位点代表一个类似σ2的结合位点。
