Ambar I, Sokolovsky M
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Eur J Pharmacol. 1993 Mar 15;245(1):31-41. doi: 10.1016/0922-4106(93)90166-7.
Endothelin (ET) receptor-binding assays using [125I]ET-1 in C6-glioma cells and in Rat-1 and Swiss 3T3 fibroblasts indicated the presence of two binding sites, one of which binds agonists at the pM range and the other at the nM range. All three cell lines exhibited the same pharmacological profile for agonist binding (ET-1 congruent to sarafotoxin-b > ET-3), which suggests that the receptor is of the ETA type. Binding of ET-1 to the receptor resulted in activation of two phospholipases, phospholipase C (PLC) and phospholipase D (PLD). The activation of PLC or PLD by endothelin in the three cell lines was mediated by the high affinity binding site (nM range) and was not significantly affected by either extracellular or intracellular Ca2+. Measurement of PLD activation by ET-1 and/or phorbol 12-myristate 13-acetate (PMA), in the presence and absence of two potent inhibitors of protein kinase C (PKC), strongly suggests that activation of PLD by ET receptor in C6 glioma cells as well as in Rat-1 and Swiss 3T3 fibroblasts involves both PKC-dependent and PKC-independent mechanisms.
使用[125I]ET-1在C6胶质瘤细胞、大鼠-1和瑞士3T3成纤维细胞中进行的内皮素（ET）受体结合试验表明存在两个结合位点，其中一个在皮摩尔范围内结合激动剂，另一个在纳摩尔范围内结合激动剂。所有三种细胞系在激动剂结合方面表现出相同的药理学特征（ET-1等同于沙罗毒素-b > ET-3），这表明该受体为ETA型。ET-1与受体的结合导致两种磷脂酶即磷脂酶C（PLC）和磷脂酶D（PLD）的激活。内皮素在这三种细胞系中对PLC或PLD的激活是由高亲和力结合位点（纳摩尔范围）介导的，并且不受细胞外或细胞内Ca2+的显著影响。在存在和不存在两种强效蛋白激酶C（PKC）抑制剂的情况下，测量ET-1和/或佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）对PLD的激活，强烈表明ET受体在C6胶质瘤细胞以及大鼠-1和瑞士3T3成纤维细胞中对PLD的激活涉及PKC依赖性和PKC非依赖性机制。
