Roubert P, Gillard V, Plas P, Auguet M, Chabrier P E, Braquet P
Institut Henri-Beaufour, Les Ulis.
Arch Mal Coeur Vaiss. 1991 Aug;84(8):1057-9.
Among the different endothelin (ET) isoforms, ET-3 has been reported to exhibit a less potent constrictor activity than ET-1 and ET-2. Furthermore, distinct endothelin receptor subtypes have been identified in several tissues or cell types. In this study, we investigated the binding characteristics of the three endothelin isoforms in cultured rat aortic smooth muscle cells. [125I]ET-3 exhibited an apparent affinity and a number of binding sites 10 and 6 times smaller, respectively, than [125I]ET-1 and [125I]ET-2. In contrast to ET-1 and ET-2, ET-3 appeared to elicit a reversible binding and did not modify ET-1 binding characteristics in receptor-regulation experiments. In competition experiments ET-1 and ET-2 equally inhibited the binding of the three endothelin isoforms, whereas ET-3 was less potent in competing with [125I]ET-1 and [125I]ET-2 than [125I]ET-3. These results suggest that rat aortic smooth muscle cells possess 2 subtypes of endothelin receptors (A and B) differing by their affinity for ET-3, their proportion, the reversibility of the binding and their sensitivity to down-regulation.
在不同的内皮素（ET）亚型中，据报道ET-3的收缩活性比ET-1和ET-2弱。此外，在几种组织或细胞类型中已鉴定出不同的内皮素受体亚型。在本研究中，我们研究了三种内皮素亚型在培养的大鼠主动脉平滑肌细胞中的结合特性。[125I]ET-3的表观亲和力和结合位点数分别比[125I]ET-1和[125I]ET-2小10倍和6倍。与ET-1和ET-2不同，ET-3似乎引起可逆性结合，并且在受体调节实验中不改变ET-1的结合特性。在竞争实验中，ET-1和ET-2同等程度地抑制三种内皮素亚型的结合，而ET-3与[125I]ET-1和[125I]ET-2竞争的能力比[125I]ET-3弱。这些结果表明，大鼠主动脉平滑肌细胞具有两种内皮素受体亚型（A和B），它们对ET-3的亲和力、比例、结合的可逆性以及对下调的敏感性不同。
