Casale T B, Hart J E
Biochem Pharmacol. 1987 Aug 1;36(15):2557-64. doi: 10.1016/0006-2952(87)90530-2.
Beta-adrenergic receptors in human peripheral lung were characterized by biochemical and radioligand assays employing binding of the beta-antagonist (-)[125I]pindolol to plasma membrane preparations. The specific binding of (-)[125I]pindolol reached equilibrium by 45 min with an initial rate constant of 0.0282 min-1. Binding was reversible with a kinetic dissociation rate constant of 0.0146 min-1. The calculated kinetic Kd (dissociation constant) was 430 pM which agreed very well with the Kd of 394 pM obtained by Scatchard analyses of equilibrium binding data. Computer analyses of equilibrium binding experiments revealed a similar Kd of 336 +/- 24 pM. The binding capacities calculated by computer analyses (155 +/- 7 fmol/mg protein) and Scatchard analyses (113 fmol/mg protein) were also in close agreement. By all three methods (kinetic, Scatchard, and computer analyses), the data were most compatible with a single (-)[125I]pindolol binding site. Analyses of equilibrium binding data from ten different human lungs revealed values for the Kd ranging from 79 to 360 pM (mean, 136 pM), and for the receptor concentration ranging from 58 to 196 fmol/mg protein (mean, 118 fmol/mg protein). The displacement of (-)[125I]pindolol binding by various agents exhibited stereoselectivity and the expected rank order of potency predicted for interactions with beta-receptors. Isoproterenol induced a rapid and dose-related increase in cyclic AMP that was prevented by specific beta-antagonists. Approximately 70% of the beta-receptors were found to be of the beta 2-subtype by both radioligand binding and biochemical assays. Thus, (-)[125I]pindolol appears to be an excellent ligand for characterizing human lung beta-receptors since accurate and reproducible results can be obtained with this radioligand using limited tissue sample quantities.
通过生化和放射性配体分析方法，利用β-拮抗剂（-）[¹²⁵I]吲哚洛尔与质膜制剂的结合，对人外周肺中的β-肾上腺素能受体进行了表征。（-）[¹²⁵I]吲哚洛尔的特异性结合在45分钟时达到平衡，初始速率常数为0.0282分钟⁻¹。结合是可逆的，动力学解离速率常数为0.0146分钟⁻¹。计算得到的动力学解离常数（Kd）为430皮摩尔，这与通过对平衡结合数据进行Scatchard分析得到的394皮摩尔的Kd非常吻合。对平衡结合实验的计算机分析显示，类似的Kd为336±24皮摩尔。通过计算机分析（155±7飞摩尔/毫克蛋白质）和Scatchard分析（113飞摩尔/毫克蛋白质）计算得到的结合容量也非常接近。通过所有三种方法（动力学、Scatchard和计算机分析），数据与单一的（-）[¹²⁵I]吲哚洛尔结合位点最为相符。对来自十个不同人肺的平衡结合数据的分析显示，Kd值范围为79至360皮摩尔（平均值为136皮摩尔），受体浓度范围为58至196飞摩尔/毫克蛋白质（平均值为118飞摩尔/毫克蛋白质）。各种试剂对（-）[¹²⁵I]吲哚洛尔结合的置换表现出立体选择性，以及与β受体相互作用所预测的预期效价顺序。异丙肾上腺素诱导环磷酸腺苷迅速且与剂量相关的增加，这被特异性β拮抗剂所阻止。通过放射性配体结合和生化分析发现，约70%的β受体为β₂亚型。因此，（-）[¹²⁵I]吲哚洛尔似乎是表征人肺β受体的一种优秀配体，因为使用这种放射性配体，利用有限的组织样本量就能获得准确且可重复的结果。
