Mittag T W, Tormay A
Exp Eye Res. 1985 Feb;40(2):239-49. doi: 10.1016/0014-4835(85)90009-0.
Receptor subclasses in iris-ciliary body cell membranes were determined by direct binding of radioactive dihydroalprenolol (DHA), yohimbine (YOH), WB-4101 WB) and prazosin (PRZ), classified respectively as beta 1 + beta 2, alpha 2, alpha 1, and alpha 1 subtype selective ligands (based on binding to brain adrenergic receptors). Specific binding was defined with appropriate unlabelled agonist and antagonist drugs in each case. Binding data were analysed by library programs of the PROPHET computer system. Subclass specificity was also determined indirectly by binding competition of the labelled ligand (at a three- to 10-fold Kd concentration) with increasing concentrations of 'cold' agonist or antagonist. Ligand binding parameters of unlabelled drugs were obtained from Dixon and Scatchard plots of the data. The adrenergic receptor density of iris-ciliary body is approx. 600 fmol mg-1 protein, of which 20-25% are primarily beta 2 receptors. Three distinct subpopulations of alpha-receptors, representing 10, 25 and 40-45% of the total, bind PRZ, WB and YOH, respectively, each with high specificity for its corresponding ligand but with 10- to 1000-fold lower specificity for the other two ligands. The majority of alpha-adrenergic receptors are of the alpha 2-subtype. A small population of receptors are similar to vascular postsynaptic alpha 1-receptors, while a larger subpopulation may have characteristics intermediate between alpha 1- and alpha 2-subtypes.
虹膜睫状体细胞膜中的受体亚类是通过放射性二氢烯丙洛尔（DHA）、育亨宾（YOH）、WB - 4101（WB）和哌唑嗪（PRZ）的直接结合来确定的，它们分别被归类为β1 +β2、α2、α1和α1亚型选择性配体（基于与脑肾上腺素能受体的结合）。在每种情况下，用适当的未标记激动剂和拮抗剂药物来定义特异性结合。结合数据通过PROPHET计算机系统的库程序进行分析。亚类特异性也通过标记配体（在其三到十倍Kd浓度下）与浓度不断增加的“冷”激动剂或拮抗剂的结合竞争来间接确定。未标记药物的配体结合参数从数据的Dixon和Scatchard图中获得。虹膜睫状体的肾上腺素能受体密度约为600 fmol mg-1蛋白质，其中20 - 25%主要是β2受体。α受体的三个不同亚群分别占总数的10%、25%和40 - 45%，分别与PRZ、WB和YOH结合，每个亚群对其相应配体具有高度特异性，但对其他两种配体的特异性低10到1000倍。大多数α肾上腺素能受体是α2亚型。一小部分受体类似于血管突触后α1受体，而更大的亚群可能具有介于α1和α2亚型之间的特征。
