Agonist versus antagonist binding to alpha-adrenergic receptors.
Agonist versus antagonist binding to alpha-adrenergic receptors.
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与α-肾上腺素能受体结合的激动剂与拮抗剂。
DOI：
10.1073/pnas.77.8.4569
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发表时间：
1980
影响因子：
11.1
通讯作者：
Fain,JN
中科院分区：
文献类型：
--
作者：
Hoffman,BB;Michel,T;Kilpatrick,DM;Lefkowitz,RJ;Tolbert,ME;Gilman,H;Fain,JN
两种α -肾上腺素能放射配体[3H]肾上腺素（一种激动剂）和[3H]二氢牛角cryptine（一种拮抗剂）的结合特性在两种模型系统——人血小板膜和大鼠肝膜中进行了比较。血小板中仅含有α 2受体，肝脏中大部分（约80%）含有α 1受体。激动剂诱导形成鸟嘌呤核苷酸敏感的高亲和力状态的α 2而不是α 1受体。[3H]二氢麦角cryptine标记所有α受体，而[3H]低浓度的肾上腺素主要标记血小板和肝脏中α 2受体的高亲和力形式。然而，在肝脏中，α -肾上腺素能的作用，如糖原磷酸化酶的激活，被证明是通过α 1受体介导的。因此，在肝膜中，使用低浓度[3H]肾上腺素进行典型的放射配体结合试验时，内源性“生理性”激动剂可能无法标记生理性相关的α 1受体。
The binding properties of two alpha-adrenergic radioligands, [3H]epinephrine (an agonist) and [3H]dihydroergocryptine (an antagonist), were compared in two model systems--membranes derived from human platelets and membranes from rat liver. The platelet contains exclusively alpha 2 and the liver mostly (approximately 80%) alpha 1 receptors. Agonists induce the formation of a guanine nucleotide-sensitive high-affinity state of alpha 2 but not alpha 1 receptors. [3H]Dihydroergocryptine labels all the alpha receptors, whereas [3H]epinephrine at low concentrations labels predominantly the high-affinity form of the alpha 2 receptor in both platelet and liver. However, in the liver, alpha-adrenergic effects such as glycogen phosphorylase activation are shown to be mediated via alpha 1 receptors. Thus, in liver membranes the endogenous "physiological" agonist may not label the physiologically relevant alpha 1 receptors in typical radioligand binding assays using low concentrations of [3H]epinephrine.