Sharif N A, Xu S X
Molecular Pharmacology Unit, Alcon Laboratories, Inc., Fort Worth, Texas 76134, USA.
J Ocul Pharmacol Ther. 1999 Jun;15(3):271-81. doi: 10.1089/jop.1999.15.271.
Polyamine binding sites (PBS) represent one of the modulatory sites on the N-methyl-D-aspartate (NMDA) receptor-channel complex. We have characterized [3H]-ifenprodil binding to the PBS on washed homogenates of rabbit and rat retinas. Specific binding of [3H]-ifenprodil (2 nM) (in the presence of 3 microM 1,3-Di [2-tolyl] guanidine HCl and 10 microM GBR12909 to block sigma sites) comprised 47-56% of the total binding. Scatchard analyses indicated interaction with apparent high- and low-affinity sites: dissociation constants (K(d)s) = 0.5-0.6 microM and apparent density of sites (Bmax) = 1.5-4.3 pmol/mg protein and K(d)s = 2.0-2.9 microM, and Bmax values = 15.8-17.8 pmol/mg protein (n = 3). Ifenprodil (Ki = 0.4-0.8 microM), eliprodil (Ki = 0.7-0.8 microM), spermine (Ki = 72-79 microM), spermidine (Ki = 283-330 microM), putrescine (Ki > 650 microM) and MK-801 (Ki > 1 mM) (n = 3-5) differentially competed for [3H]-ifenprodil binding. The biphasic competition curves for ifenprodil were resolved into two binding components: rat retinas, IC50high = 0.19 +/- 0.13 microM and IC50low = 8.7 +/- 1.3 microM; rabbit retinas, IC50high = 0.1 +/- 0.01 microM and IC50low = 16.0 +/- 7.8 microM. These studies have shown the presence of specific PBS labeled by [3H]-ifenprodil in the rabbit and rat retinas which may, in part, be responsible for mediating the neuroprotective effects of eliprodil and ifenprodil.
多胺结合位点（PBS）是N-甲基-D-天冬氨酸（NMDA）受体通道复合物上的调节位点之一。我们已对[3H] - 艾芬地尔与兔和大鼠视网膜匀浆洗涤物上的PBS结合进行了表征。[3H] - 艾芬地尔（2 nM）（在存在3 microM 1,3 - 二[2 - 甲苯基]胍盐酸盐和10 microM GBR12909以阻断σ位点的情况下）的特异性结合占总结合的47 - 56％。Scatchard分析表明与明显的高亲和力和低亲和力位点相互作用：解离常数（K(d)s）= 0.5 - 0.6 microM，位点表观密度（Bmax）= 1.5 - 4.3 pmol/mg蛋白质，K(d)s = 2.0 - 2.9 microM，Bmax值= 15.8 - 17.8 pmol/mg蛋白质（n = 3）。艾芬地尔（Ki = 0.4 - 0.8 microM）、依立普地尔（Ki = 0.7 - 0.8 microM）、精胺（Ki = 72 - 79 microM）、亚精胺（Ki = 283 - 330 microM）、腐胺（Ki > 650 microM）和MK - 801（Ki > 1 mM）（n = 3 - 5）对[3H] - 艾芬地尔结合的竞争存在差异。艾芬地尔的双相竞争曲线解析为两个结合成分：大鼠视网膜，IC50高 = 0.19 +/- 0.13 microM，IC50低 = 8.7 +/- 1.3 microM；兔视网膜，IC50高 = 0.1 +/- 0.01 microM，IC50低 = 16.0 +/- 7.8 microM。这些研究表明兔和大鼠视网膜中存在由[3H] - 艾芬地尔标记的特异性PBS，这可能部分负责介导依立普地尔和艾芬地尔的神经保护作用。
