title: Endothelin-1 and -3 binding to ETB receptors in rat renal tubules.
abstract: To increase understanding of endothelin (ET) function in the kidney, we investigated binding of the radioligand of endothelin isopeptides to microdissected rat nephron segments. Specific ET-1 binding was highest in the inner medullary collecting duct, whereas the cortical and outer medullary collecting ducts showed moderate binding, as did the glomeruli. There was slight ET-1 binding to the early portion of the proximal tubule. Other nephron segments displayed little ET-1 binding. The binding profile of ET-3 along the nephron markedly resembled that of ET-1. Scatchard analyses of ET-1 and ET-3 binding to cortical collecting ducts revealed a single class of receptor for both ET-1 and ET-3. Displacement of [125I]-ET-1 binding by unlabeled ET-3 was similar to that produced by unlabeled ET-1. Moreover, a specific ETB agonist, BQ-3020, almost completely inhibited [125I]-ET-1 binding in cortical collecting ducts, whereas a specific ETA antagonist, BQ-123, had little effect. These data indicate that cortical collecting ducts express ETB receptors, to which both ET-1 and ET-3 bind equally.
authors.affiliation: First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Uchida
authors.forename: F
authors.initials: F
authors.lastname: Takemoto
authors.forename: E
authors.initials: E
authors.lastname: Ogata
authors.forename: K
authors.initials: K
authors.lastname: Kurokawa
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000378:metabolism* / Q000494:pharmacology; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007678:Kidney Glomerulus / Q000187:drug effects / Q000378:metabolism; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism*; D009399:Nephrons / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D051381:Rats; D017466:Receptors, Endothelin / Q000187:drug effects / Q000378:metabolism*
chemical_list: D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D017466:Receptors, Endothelin; C075771:BQ 3020; C072247:cyclo(Trp-Asp-Pro-Val-Leu)