High-affinity binding of agonists to beta-adrenergic receptors on intact cells.
High-affinity binding of agonists to beta-adrenergic receptors on intact cells.
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激动剂与完整细胞上的 β-肾上腺素能受体高亲和力结合。
DOI：
10.1073/pnas.80.12.3553
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发表时间：
1983
影响因子：
11.1
通讯作者：
Perkins,JP
中科院分区：
文献类型：
--
作者：
Toews,ML;Harden,TK;Perkins,JP
利用放射性配体(-)-[125I]碘啶多洛研究了受体激动剂和拮抗剂与β -肾上腺素能受体在完整的1321N1人星形细胞瘤和C62B大鼠胶质瘤细胞上的相互作用。竞争结合实验在37摄氏度的平衡条件下进行，在短时间的非平衡分析中，近似于辐射配体结合的初始速度条件。给出了测定快速平衡配体结合亲和力的初速度法的理论基础和实验验证。对于激动剂异丙肾上腺素和肾上腺素，只有在短时间的实验中才能证明它们的高结合亲和力接近于它们在膜上的结合和在完整细胞中环AMP浓度的增加；相比之下，在平衡（60分钟）分析中观察到的亲和力要低得多，如先前报道的各种细胞系。在冰上进行的平衡（6小时）结合实验中也观察到异丙肾上腺素与1321N1细胞的高亲和力结合。这些结果表明，在天然状态下，完整细胞β -肾上腺素能受体对激动剂具有高结合亲和力，并且表明在37℃的孵育下，在激动剂的存在下，受体转化为对激动剂具有低亲和力的形式。
The interactions of agonists and antagonists with beta-adrenergic receptors on intact 1321N1 human astrocytoma and C62B rat glioma cells were studied by using the radioligand (-)-[125I]iodopindolol. Competition binding assays were performed at 37 degrees C under equilibrium conditions and in short-time nonequilibrium assays that approximated initial velocity conditions for binding of the radioligand. The theoretical basis and experimental validation of the initial velocity approach for determining binding affinities of rapidly equilibrating ligands are presented. For the agonists isoproterenol and epinephrine, high binding affinities that approximated their apparent affinities for binding in membranes and for increase of cyclic AMP concentrations in intact cells could be demonstrated only in short-time assays; in contrast, much lower affinities were observed with equilibrium (60-min) assays as reported previously for various cell lines. High-affinity binding of isoproterenol to 1321N1 cells also was observed in equilibrium (6-hr) binding assays carried out on ice. These results indicate that in the native state the intact cell beta-adrenergic receptor has a high binding affinity for agonists and suggest that incubation at 37 degrees C in the presence of an agonist converts the receptors to a form with low affinity for agonists.