Reith M E, Coffey L L
Department of Basic Sciences, University of Illinois College of Medicine, Peoria 61656.
J Neurochem. 1993 Jul;61(1):167-77. doi: 10.1111/j.1471-4159.1993.tb03552.x.
The present study reports the ion dependency of 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)[3H]tropane ([3H]CFT) binding to the dopamine transporter in the rat striatum. The results indicate that [3H]CFT binding to synaptosomal P2 membranes requires low concentrations of Na+ (peak binding between 20 and 50 mM Na+), is stimulated by phosphate anion or I-, but is unaffected or only slightly affected by F-, Cl-, Br-, NO3-, or SO(4)2-. Concentrations of Na+ of > 50 mM become inhibitory except in the presence of I-, which shifts peak binding levels toward higher Na+ concentrations and also elevates the peak binding level. K+ strongly decreased [3H]CFT binding with a shallow inhibition curve, and Na+ could not overcome this effect. Saturation analysis of [3H]CFT binding revealed a single binding site changing its affinity for CFT depending on the concentration of sodium phosphate buffer (6, 10, 30, 50, 130, or 200 mM; 1 mM plus 49 mM NaCl versus 10 mM plus 40 mM NaCl; or 1 mM plus 129 mM NaI versus 10 mM plus 120 mM NaI). No differences were observed in the density of CFT binding sites between any of the conditions examined.
本研究报告了2β-甲氧羰基-3β-(4-氟苯基)[3H]托烷([3H]CFT)与大鼠纹状体中多巴胺转运体结合的离子依赖性。结果表明，[3H]CFT与突触体P2膜的结合需要低浓度的Na+(在20至50 mM Na+之间达到结合峰值)，受磷酸根阴离子或I-刺激，但不受F-、Cl-、Br-、NO3-或SO(4)2-影响或仅略有影响。除了在I-存在的情况下，Na+浓度>50 mM会产生抑制作用，I-会使结合峰值水平向更高的Na+浓度偏移，同时也会提高结合峰值水平。K+强烈降低[3H]CFT结合，抑制曲线较平缓，且Na+无法克服这种效应。[3H]CFT结合的饱和分析显示，存在一个单一结合位点，其对CFT的亲和力会根据磷酸钠缓冲液的浓度(6、10、30、50、130或200 mM；1 mM加49 mM NaCl与10 mM加40 mM NaCl；或1 mM加129 mM NaI与10 mM加120 mM NaI)而改变。在所检测的任何条件下，CFT结合位点的密度均未观察到差异。
