Endothelin receptors in human smooth muscle cells: antagonist potency differs on agonist-evoked responses.
The present study characterized endothelin (ET) receptors in human pericardium smooth muscle cells (HPSMC) and examined the potency of antagonists on ET-evoked signal transduction and DNA synthesis. HPSMC contain both ETA and ETB receptors. ET-1 binding was completely inhibited by a nonselective antagonist (Ro-46-2005) or a combination of ETA-selective and ETB-selective ligands (BQ-123 and ET-3). The molecular masses for ETA and ETB receptors were 69 and 42 kDa, respectively. ET-1, but not ET-3, stimulated phosphatidylinositol hydrolysis and arachidonic acid release in a dose- and time-dependent manner, reaching a plateau within 20-40 min. These immediate effects of ET-1 on signal transduction were completely inhibited by 1 microM, BQ-123, ET-1, but not ET-3, stimulated DNA synthesis in a dose-dependent manner, and the effect became prominent after 24 h. BQ-123 (1 microM) or Ro-46-2005 (10 microM) did not completely inhibit this mitogenic effect of ET-1. The reduced potency of BQ-123 and Ro-46-2005 on the delayed effect of ET-1 was not the result of ligand degradation or a difference in receptor internalization; rather, the decrease in potency was due to the fact that antagonist binding was more reversible than ET-1 binding.
Wu-Wong
J R
JR
Pharmaceutical Products Division, Abbott Laboratories, Abbott Park, Illinois 60064.
Chiou
W J
WJ
Huang
Z J
ZJ
Vidal
M J
MJ
Opgenorth
T J
TJ
D001665:Binding Sites; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000494:pharmacology*; D006801:Humans; D008024:Ligands; D008970:Molecular Weight; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000494:pharmacology; D010496:Pericardium / Q000166:cytology / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D017466:Receptors, Endothelin / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D000096926:Benzenesulfonamides
D004247:DNA; D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D008024:Ligands; D010456:Peptides, Cyclic; D011743:Pyrimidines; D017466:Receptors, Endothelin; D013449:Sulfonamides; C083751:Ro 46-2005; D000096926:Benzenesulfonamides; C072247:cyclo(Trp-Asp-Pro-Val-Leu)