Kinetic studies of co-operativity at atrial muscarinic M(2) receptors with an ''infinite dilution'' procedure
Kinetic studies of co-operativity at atrial muscarinic M(2) receptors with an ''infinite dilution'' procedure
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DOI：
10.1016/s0006-2952(96)00814-3
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发表时间：
1997-03-21
影响因子：
5.8
通讯作者：
Mitchelson, F
中科院分区：
文献类型：
--
作者：
Christopoulos, A;Lanzafame, A;Mitchelson, F
通过“无限稀释”技术，研究了两种竞争性拮抗剂和两种变构配体对心房毒蕈碱乙酰胆碱 M(2) 受体中 [H-3]N-甲基东莨菪碱 ([H-3]NMS) 解离速率的影响。 [H-3]NMS 的解离速率通过将孵育混合物稀释 100 倍来启动 缓冲液体积为 0.61 +/- 0.10 分钟(-1)。在稀释介质中添加竞争性拮抗剂阿托品或 NMS 不会改变观察到的 [H-3]NMS 解离速率。相比之下，没食子胺和双季铵基庚烷-1,7-双-(二甲基-3'-邻苯二甲酰亚氨基丙基-溴化铵) (C-7/3'-phth) 产生浓度依赖性的 [H-3]NMS 解离速率减慢，IC50 值分别为 7.5 μM 和 196 nM。当稀释前与组织达到平衡时，没食子胺表现出增强的调节效力。研究结果表明，低浓度变构调节剂对 [H-3]NMS 解离速率的影响可以与对结合速率的任何影响分开证明，并且与变构配体的接触时间可能影响这些影响的程度。 (C) 1997 爱思唯尔科学公司。
The effects of two competitive antagonists and two allosteric ligands on the rate of dissociation of [H-3]N-methylscopolamine ([H-3]NMS) were studied at atrial muscarinic acetylcholine M(2) receptors by the technique of ''infinite dilution.'' The dissociation rate for [H-3]NMS, initiated by diluting the incubation mixture in a 100-fold volume of buffer, was 0.61 +/- 0.10 min(-1). Addition of the competitive antagonists, atropine or NMS, to the dilution medium did not alter the observed [H-3]NMS dissociation rate. In contrast, gallamine and the bisquaternary, heptane-1,7-bis-(dimethyl-3'-phthalimidopropyl-ammonium bromide) (C-7/3'-phth), produced a concentration-dependent slowing of the dissociation rate of [H-3]NMS, with IC50 values of 7.5 mu M and 196 nM, respectively. Gallamine exhibited an increased modulatory potency when equilibration with the tissue was allowed prior to dilution. The findings showed that the influence of low concentrations of allosteric modulators on the [H-3]NMS dissociation rate may be demonstrated separately from any effects on association rate, and that the contact time with the allosteric ligand may influence the extent of these effects. (C) 1997 Elsevier Science Inc.