title: Salicylic acid alters endothelin-1 binding in intact adult rat ventricular myocytes.
abstract: Endothelin receptors ET(A)R and ET(B)R form tight receptor-ligand complexes that complicate our understanding of the physiological, pharmacological, and biochemical properties of these receptors. Although radioligand-binding studies have demonstrated the binding of endothelin-1 (ET-1) to ET(A)R to be essentially irreversible, ET(A)R internalize in a ligand-dependent manner, release ET-1, and then recycle to the cell surface. Salicylic acid (SA) reduces ET-1 binding (IC(50) = 10 mmol/L) to recombinant ET(A)R in isolated membranes by promoting dissociation of [(125)I]ET-1. In the present study, SA (5 mmol SA/L) did not alter [(125I)]ET-1 binding to intact adult rat ventricular myocytes. The lack of effect was not due to internalization of receptor-ligand complexes. However, 100 mmol SA/L significantly reduced [(125)I]ET-1 binding to both intact myocytes and isolated membranes. SA induced the phosphorylation p42/44 extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase and an unidentified 40-kDa protein on the activating threonine-glutamic acid-tyrosine (T-E-Y) motif. ERK phosphorylation was reduced by a MAP kinase kinase (MEK) inhibitor, PD98059. Phosphorylation of p40 was reduced by the p38 MAP kinase inhibitor SB203580, but not PD98059. However, inhibition of ERK or p38 MAP kinases did not alter the ability of 100 mmol SA/L to induce dissociation of [125I]ET-1. These results suggest that, in the ventricular myocyte, salicylic acid alters the kinetics of ET-1 binding. The results also suggest an allosteric binding site may be present that modulates the dissociation of ET-1 receptor-ligand complexes in response to an as-of-yet unidentified mediator.
authors.affiliation: Department of Biochemistry, Université de Montréal, Montréal, QC H3C 3J7, Canada.
authors.forename: Hala
authors.initials: H
authors.lastname: Farhat
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Allen
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D019332:Endothelin-1 / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000378:metabolism*; D020156:Salicylic Acid / Q000494:pharmacology*; D013696:Temperature
chemical_list: D019332:Endothelin-1; D005419:Flavonoids; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; D017466:Receptors, Endothelin; C015482:protein kinase modulator; D048049:Extracellular Signal-Regulated MAP Kinases; D020156:Salicylic Acid; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one