Hirata Y, Yoshimi H, Takaichi S, Yanagisawa M, Masaki T
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
FEBS Lett. 1988 Oct 24;239(1):13-7. doi: 10.1016/0014-5793(88)80536-2.
Binding of a novel endothelium-derived vasoconstrictor endothelin (ET) and the regulation of its receptor were studied in cultured rat vascular smooth muscle cells. 125I-labeled-ET bound to the cells was resistant to acid extraction and the majority of the acid-resistant compartment was extractable with chloroform/methanol with minimal degradation. Autoradiographic studies using electron microscopy revealed that the grains were predominantly localized in the plasma membranes, but some were adjacent to and within the lysosome. Pretreatment with ET resulted in a substantial reduction of ET receptor number without changing its binding affinity. ET-induced increase in cytosolic free Ca2+ levels [( Ca2+]i] was absent or attenuated in the ET-pretreated cells. These data suggest that tight association of ET with its receptor is due to a strong interaction of its hydrophobic domain with the membrane lipids and/or its internalization within cells and that down-regulation of ET receptor is functionally linked to decreased ET-induced [Ca2+]i response.
在培养的大鼠血管平滑肌细胞中研究了一种新型内皮源性血管收缩因子内皮素（ET）的结合及其受体的调节。与细胞结合的125I标记的ET对酸提取具有抗性，并且大部分耐酸区室可用氯仿/甲醇提取，降解最少。使用电子显微镜的放射自显影研究表明，颗粒主要定位于质膜，但有些颗粒与溶酶体相邻并位于溶酶体内。用ET预处理导致ET受体数量大幅减少，而其结合亲和力不变。在ET预处理的细胞中，ET诱导的细胞溶质游离Ca2+水平[（Ca2+]i]的增加不存在或减弱。这些数据表明，ET与其受体的紧密结合是由于其疏水结构域与膜脂的强烈相互作用和/或其在细胞内的内化，并且ET受体的下调在功能上与ET诱导的[Ca2+]i反应降低有关。
