Endothelin-1 binding to endothelin receptors in the rat anterior pituitary gland: interaction in the recognition of endothelin-1 between ETA and ETB receptors.
1. 125I-Endothelin (ET)-1 binding to the rat anterior pituitary gland was saturable and single, with a Kd of 71 pM and a Bmax of 120 fmol/mg. 2. When 1.0 microM BQ-123 (ETA antagonist) was added to the incubation buffer, the binding parameters were 8.3 pM and 8.0 fmol/mg, whereas 10 nM sarafotoxin S6c (ETB agonist) exerted little change in these binding parameters (Kd, 72 pM; Bmax, 110 fmol/mg). 3. ETB receptor-related compounds such as sarafotoxin S6c, ET-3, IRL1620, and BQ-788 competitively inhibited 125I-ET-1 binding, only when 1.0 microM BQ-123 was present in the incubation buffer. 4. Thus, the ETB receptor is capable of binding ET-1 when the ETA receptor is being occupied by BQ-123. A collaboration mechanism between the ETA and the ETB receptor may function in the recognition of ET-1, a typical "bivalent" ligand.
Himeno
A
A
Department of Pharmacology 1, Nagasaki University School of Medicine, Japan.
Shigematsu
K
K
Taguchi
T
T
Niwa
M
M
D000818:Animals; D001667:Binding, Competitive; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000378:metabolism*; D019334:Endothelin-3 / Q000494:pharmacology; D016232:Endothelins / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000378:metabolism*; D014757:Viper Venoms / Q000494:pharmacology
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D019334:Endothelin-3; D016232:Endothelins; D009842:Oligopeptides; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D010880:Piperidines; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D014757:Viper Venoms; C057354:sarafotoxins s6; C074308:sovateltide; C086539:BQ 788; C072247:cyclo(Trp-Asp-Pro-Val-Leu)