Takayanagi R, Ohnaka K, Takasaki C, Ohashi M, Nawata H
Third Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Regul Pept. 1991 Jan 1;32(1):23-37. doi: 10.1016/0167-0115(91)90004-z.
To clarify the existence and the distribution of endothelin (ET) receptor subtypes, we have examined the pharmacological properties and the molecular weight (Mr) of 125I-ET-1 and 125I-ET-3 binding sites in various tissues of pigs. ET-1 and ET-2 showed almost identical potencies in displacing the bound 125I-ET-1 in all the tissues examined. ET-3, sarafotoxin S6b (SRT-b) and sarafotoxin S6c (SRT-c) displaced the 125I-ET-1 with the same sensitivity as ET-1 (IC50 = 0.1-1.4 nM) in brain, kidney, liver and adrenal, whereas the three peptides showed very weak competition (IC50 = 40-500 nM) against 125I-ET-1 binding in cardiac atria, aorta, lung, stomach and uterus. The computer analyses of the binding data suggested the presence of high (Kd1 = 0.04-0.29 nM) and low (Kd2 = 60-190 nM) affinity binding sites for ET-3 and SRT-b in lung and stomach. 125I-ET-3 bound to the high affinity sites in lung and stomach was displaced by ET/SRT isopeptides almost equipotently. Two proteins with Mr of 47,000 and 35,000 were affinity-labeled with 125I-ET-1 in cerebellum, while a protein with Mr of 123,000, in addition to the two proteins, was predominantly labeled in lung. The above findings indicated that two distinct subclasses of ET receptors, namely, ET-1-specific and ET/SRT family-common receptors were distributed in various proportions in mammalian tissues, and suggested that their molecular forms are also different.
为阐明内皮素（ET）受体亚型的存在及其分布，我们研究了猪各种组织中125I-ET-1和125I-ET-3结合位点的药理学特性及分子量（Mr）。在所有检测的组织中，ET-1和ET-2在置换结合的125I-ET-1时表现出几乎相同的效力。在脑、肾、肝和肾上腺中，ET-3、铃蟾毒素S6b（SRT-b）和铃蟾毒素S6c（SRT-c）与ET-1以相同的敏感性置换125I-ET-1（IC50 = 0.1 - 1.4 nM），而这三种肽在心房、主动脉、肺、胃和子宫中对125I-ET-1结合的竞争作用非常弱（IC50 = 40 - 500 nM）。结合数据的计算机分析表明，在肺和胃中存在ET-3和SRT-b的高亲和力（Kd1 = 0.04 - 0.29 nM）和低亲和力（Kd2 = 60 - 190 nM）结合位点。肺和胃中与高亲和力位点结合的125I-ET-3几乎被ET/SRT异肽等电位置换。在小脑中，两种分子量分别为47,000和35,000的蛋白质被125I-ET-1亲和标记，而在肺中，除了这两种蛋白质外，一种分子量为123,000的蛋白质被大量标记。上述发现表明，ET受体的两个不同亚类，即ET-1特异性受体和ET/SRT家族共同受体，以不同比例分布于哺乳动物组织中，并且提示它们的分子形式也不同。
