title: Characterization of endothelin 1 receptor and signal transduction mechanisms in rat medullary interstitial cells.
abstract: Previous autoradiographic studies have delineated the renal medullas the predominant site of renal endothelin (ET) receptors. Accordingly, cultured rat renal medullary interstitial cells (RMICs) were studied as a target tissue for ET action. Scatchard analysis revealed presence of a single class of high-affinity receptor sites (Kd, 57 +/- 10 pM; receptor density, 749 +/- 124 fmol/mg protein). Relative potency order for displacing 125I-ET-1 was ET-1 greater than ET-2 greater than sarafotoxin greater than big endothelin (human) = big endothelin (porcine). ET-3, unrelated pressor substances, vasodilators, Ca2+ channel antagonists, atrial natriuretic factor, GTP, and GppNHp did not inhibit binding. Challenge of monolayers with ET-1 evoked a biphasic elevation in cytosolic free Ca2+ concentration [Ca2+]i). Initial transient rise in [Ca2+]i observed in absence of extracellular Ca2+ and accumulation of inositol trisphosphate (IP3) was consistent with activation of phosphatidylinositol-specific phospholipase C (PI-PLC). Half-maximal activation concentration of ET-1 for the process was 0.5 and 1 nM for [Ca2+]i and IP3, respectively. The late sustained phase in [Ca2+]i elevation was completely blocked by Ni2+, unperturbed by nimodipine, and accompanied by influx of Mn2+, indicating presence of receptor-operated Ca2+ channels. Ca2+ channel opening was detected at 10(-16) MET-1, whereas greater than 10(-12) M agonist was required to mobilize Ca2+ from intracellular stores and/or stimulate phosphoinositol hydrolysis, indicating that ET activation of PI-PLC and Ca2+ channel opening were independent events. ET-1 markedly stimulated prostaglandin E2 synthesis in a concentration-dependent manner that paralleled PI-PLC activation and mobilization of [Ca2+]i. In summary, cultured rat RMICs possess ET receptors that are linked to PI-PLC, Ca2+ channels, and perhaps phospholipase A2.
authors.affiliation: Department of Medicine, North Shore University Hospital, Manhasset, New York.
authors.forename: B M
authors.initials: BM
authors.lastname: Wilkes
authors.forename: A S
authors.initials: AS
authors.lastname: Ruston
authors.forename: P
authors.initials: P
authors.lastname: Mento
authors.forename: E
authors.initials: E
authors.lastname: Girardi
authors.forename: D
authors.initials: D
authors.lastname: Hart
authors.forename: M
authors.initials: M
authors.lastname: Vander Molen
authors.forename: R
authors.initials: R
authors.lastname: Barnett
authors.forename: E P
authors.initials: EP
authors.lastname: Nord
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D015232:Dinoprostone / Q000096:biosynthesis; D016232:Endothelins / Q000378:metabolism / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism*; D007700:Kinetics; D008345:Manganese / Q000378:metabolism; D009532:Nickel / Q000494:pharmacology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000502:physiology*; D017466:Receptors, Endothelin; D015398:Signal Transduction
chemical_list: D015220:Calcium Channels; D016232:Endothelins; D007295:Inositol Phosphates; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin; D008345:Manganese; D009532:Nickel; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D015232:Dinoprostone; D002118:Calcium