title: Demonstration and characterization of two classes of cardiac glycoside binding sites to rat heart membrane preparations using quantitative computer modeling.
abstract: Cardiac glycoside binding to rat heart membrane preparations was measured by rapid filtration technique. The binding data were analyzed using quantitative computer analysis. The experimental results using [3H]-ouabain as the labeled ligand were consistent with a model in which cardiac glycoside specific binding occurs at two independent classes of sites. The high affinity sites were characterized by a dissociation constants of 40 nM, 50 nM, and 61 nM for ouabain, digoxin and digitoxin, respectively, with a binding capacity of 1.3 pmoles/mg protein. The lower affinity sites for ouabain were characterized by dissociation constants of 2.3 microM, 67 nM and 71 nM for ouabain, digoxin and digitoxin, respectively, with a binding capacity of 3 pmoles/mg protein. Potassium ions inhibit [3H]-ouabain binding in a dose dependent manner with an IC50 of 500 microM. Quantitative computer modelling indicated that potassium inhibits ouabain binding at both binding sites.
authors: Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, Bethesda, MD 20892.
authors: R A
authors: RA
authors: Lutz
authors: D
authors: D
authors: Lichtstein
authors: H
authors: H
authors: Xu
authors: D
authors: D
authors: Rodbard
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002301:Cardiac Glycosides / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004074:Digitoxin / Q000378:metabolism; D004077:Digoxin / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010042:Ouabain / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011955:Receptors, Drug / Q000187:drug effects / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase; D012984:Software
chemical_list: D002301:Cardiac Glycosides; D011955:Receptors, Drug; C028996:cardiac glycoside receptors; D010042:Ouabain; D004077:Digoxin; D004074:Digitoxin; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium