Wu-Wong J R, Chiou W, Magnuson S R, Bianchi B R, Lin C W
Pharmaceutical Products Division, Abbott Laboratories, Abbott Park, IL 60064, USA.
Biochim Biophys Acta. 1996 May 28;1311(3):155-63. doi: 10.1016/0167-4889(95)00202-2.
Endothelin-1 (ET-1) binding to human astrocytoma U138MG cells was time-dependent, and bound [125I]ET-1 was difficult to dissociate. The B(max) and Kd values of [125I]ET-1 binding were 70 fmol/mg and 0.07 nM, respectively. Interestingly, different from other astrocytoma cells and astrocytes, the U138MG cells expressed predominantly ETA receptor as shown by RT-PCR results and binding studies. ET-1, FR139317, BQ123, PD142893 and Ro46-2005 inhibited specific [125I]ET-1 binding with Ki values of 0.10, 0.53, 4.3, 22, and 320 nM, respectively. ETB selective ligands ET-3 and IRL1620 were much less potent. The inhibitory effects of antagonists BQ123 and PD142893 on [125I]ET-1 binding diminished following the incubation time. ET-1 binding caused a modest stimulation in phosphatidylinositol hydrolysis with an EC50 value of 24 nM. In comparison to the human U373MG cells, ET-1-induced receptor internalization in U138MG cells was less efficient with 42% of bound ET-1 internalized after 30 min of incubation. These results imply that human astrocytoma cells/astrocytes are able to express either ETA or ETB receptor under different pathophysiological conditions.
内皮素 -1（ET -1）与人星形细胞瘤U138MG细胞的结合具有时间依赖性，且结合的[125I]ET -1难以解离。[125I]ET -1结合的B(max)和Kd值分别为70 fmol/mg和0.07 nM。有趣的是，与其他星形细胞瘤细胞和星形胶质细胞不同，RT-PCR结果和结合研究表明，U138MG细胞主要表达ETA受体。ET -1、FR139317、BQ123、PD142893和Ro46 - 2005抑制特异性[125I]ET -1结合，其Ki值分别为0.10、0.53、4.3、22和320 nM。ETB选择性配体ET -3和IRL1620的效力要低得多。拮抗剂BQ123和PD142893对[125I]ET -1结合的抑制作用随孵育时间而减弱。ET -1结合对磷脂酰肌醇水解有适度刺激，EC50值为24 nM。与人类U373MG细胞相比，ET -1诱导的U138MG细胞受体内化效率较低，孵育30分钟后，42%的结合ET -1被内化。这些结果表明，在不同的病理生理条件下，人类星形细胞瘤细胞/星形胶质细胞能够表达ETA或ETB受体。
