Jensen N, Hasselblatt M, Sirén A L, Schilling L, Schmidt M, Ehrenreich H
Department of Neurology, Georg-August-University, and Max-Planck-Institute for Experimental Medicine, Göttingen, Germany.
J Neurochem. 1998 Feb;70(2):473-82. doi: 10.1046/j.1471-4159.1998.70020473.x.
Using a whole-cell binding procedure with long incubations at low temperature and subsequent acid stripping, we have characterized an atypical endothelin (ET) receptor in primary rat cortical astrocyte cultures. We found the following: (a) no competition for 125I-ET-1 binding by the ET(A) antagonists BQ-123 and LU 135252 or the ET(B) agonist IRL 1620; (b) weak competition by the ET(B) antagonist BQ-788 and by the predominant ET(B) ligand ET-3; (c) potent synergistic competition of ET(A) and ET(B) ligands in combination for 125I-ET-1 binding; (d) potent competition of ET-1 with any of the radioligands used, 125I-ET-1, 125I-IRL 1620, and [3H]BQ-123; (e) lack of competition of IRL 1620 and BQ-123 with the respective other radioligand; (f) shifting of the amount of acid-strippable 125I-ET-1 binding from 20 to 80% by ET(B) ligands and to 4% by ET(A) ligands; and (g) as a control, typical ET(A) and ET(B) binding characteristics of the RAT-1 fibroblast and the U373MG astrocytoma cell line, respectively, under our assay conditions. The unusual binding properties of astrocytic ET receptors described in this study appear to be the result of several binding sites in the receptor for different ET ligands or ligand epitopes.
通过在低温下长时间孵育并随后进行酸洗脱的全细胞结合程序，我们对原代大鼠皮质星形胶质细胞培养物中的一种非典型内皮素（ET）受体进行了表征。我们发现以下几点：（a）ET（A）拮抗剂BQ - 123和LU 135252或ET（B）激动剂IRL 1620对125I - ET - 1结合无竞争作用；（b）ET（B）拮抗剂BQ - 788和主要的ET（B）配体ET - 3有较弱的竞争作用；（c）ET（A）和ET（B）配体联合对125I - ET - 1结合有强大的协同竞争作用；（d）ET - 1与所用的任何放射性配体（125I - ET - 1、125I - IRL 1620和[3H]BQ - 123）有强大的竞争作用；（e）IRL 1620和BQ - 123与各自的其他放射性配体无竞争作用；（f）ET（B）配体可使酸可洗脱的125I - ET - 1结合量从20%变为80%，ET（A）配体可使其变为4%；（g）作为对照，在我们的测定条件下，RAT - 1成纤维细胞和U373MG星形细胞瘤细胞系分别具有典型的ET（A）和ET（B）结合特性。本研究中描述的星形胶质细胞ET受体的异常结合特性似乎是受体中不同ET配体或配体表位的多个结合位点的结果。
