Human astrocytoma U138MG cells express predominantly type-A endothelin receptor.
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.
Wu-Wong
J R
JR
Pharmaceutical Products Division, Abbott Laboratories, Abbott Park, IL 60064, USA.
Chiou
W
W
Magnuson
S R
SR
Bianchi
B R
BR
Lin
C W
CW
D001254:Astrocytoma / Q000378:metabolism*; D001483:Base Sequence; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004705:Endocytosis / Q000187:drug effects; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000378:metabolism* / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008024:Ligands; D008969:Molecular Sequence Data; D010716:Phosphatidylinositols / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011743:Pyrimidines; D012333:RNA, Messenger / Q000032:analysis; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000378:metabolism*; D013449:Sulfonamides; D014407:Tumor Cells, Cultured; D000096926:Benzenesulfonamides
D005576:Colforsin; D000242:Cyclic AMP; D017931:DNA Primers; D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D006165:Guanylyl Imidodiphosphate; D006632:Histamine; D007545:Isoproterenol; D008024:Ligands; D010716:Phosphatidylinositols; D011743:Pyrimidines; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D013449:Sulfonamides; C083751:Ro 46-2005; D000096926:Benzenesulfonamides