Biomaterial Database

Influence of quinidine on the binding of [3H]-ouabain and [3H]-digoxin by human lymphocytes. 1983

K E Pedersen, and N A Klitgaard

To explore the molecular basis of the glycoside-quinidine interaction, the in vitro effect of quinidine on the binding of [3H]-ouabain and [3H]-digoxin to Na + K + ATPase receptors on human mononuclear cells was investigated. The maximum [3H]-ouabain binding capacity was 45.7 +/- 9.4 X 10(3) molecules/cell in pure lymphocyte preparations (n = 8) and 75.5 +/- 7.3 X 10(3) molecules/cell in mixtures of mononuclear cells (n = 8). These parameters were not influenced by 10(-5)M quinidine. In eight equilibrium experiments with pure lymphocytes, the dissociation constant of [3H]-ouabain increased from 0.79 +/- 0.26 X 10(-8)M in the absence of 10(-5)M quinidine to 1.56 +/- 0.74 X 10(-8)M in its presence (p less than 0.01), indicating that the affinity of the drug was decreased. Similar findings were observed using mixed mononuclear cells. In five uptake and release experiments, quinidine decreased the association rate constant of [3H]-ouabain from 3.15 +/- 0.36 X 10(4)M-1 X s-1 to 2.01 +/- 0.37 X 10(4)M-1 s-1 (p less than 0.01), whereas the dissociation rate constant was not affected. A therapeutic concentration of quinidine does not affect the number of glycoside receptors on lymphocytes, but it does appear to reduce fractional receptor occupancy by both [3H]-ouabain and [3H]-digoxin at lower tracer concentrations. This finding is compatible with the clinical observation that quinidine reduces the distribution volume of digoxin.

UI	MeSH Term	Description	Entries
D008214	Lymphocytes	White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS.	Lymphoid Cells,Cell, Lymphoid,Cells, Lymphoid,Lymphocyte,Lymphoid Cell
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
D011802	Quinidine	An optical isomer of quinine, extracted from the bark of the CHINCHONA tree and similar plant species. This alkaloid dampens the excitability of cardiac and skeletal muscles by blocking sodium and potassium currents across cellular membranes. It prolongs cellular ACTION POTENTIALS, and decreases automaticity. Quinidine also blocks muscarinic and alpha-adrenergic neurotransmission.	Adaquin,Apo-Quinidine,Chinidin,Quincardine,Quinidex,Quinidine Sulfate,Quinora,Apo Quinidine,Sulfate, Quinidine
D004077	Digoxin	A cardiotonic glycoside obtained mainly from Digitalis lanata; it consists of three sugars and the aglycone DIGOXIGENIN. Digoxin has positive inotropic and negative chronotropic activity. It is used to control ventricular rate in ATRIAL FIBRILLATION and in the management of congestive heart failure with atrial fibrillation. Its use in congestive heart failure and sinus rhythm is less certain. The margin between toxic and therapeutic doses is small. (From Martindale, The Extra Pharmacopoeia, 30th ed, p666)	Digacin,Digitek,Digoregen,Digoxina Boehringer,Digoxine Nativelle,Dilanacin,Hemigoxine Nativelle,Lanacordin,Lanicor,Lanoxicaps,Lanoxin,Lanoxin-PG,Lenoxin,Mapluxin,Boehringer, Digoxina,Lanoxin PG,Nativelle, Digoxine,Nativelle, Hemigoxine
D004347	Drug Interactions	The action of a drug that may affect the activity, metabolism, or toxicity of another drug.	Drug Interaction,Interaction, Drug,Interactions, Drug
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000254	Sodium-Potassium-Exchanging ATPase	An enzyme that catalyzes the active transport system of sodium and potassium ions across the cell wall. Sodium and potassium ions are closely coupled with membrane ATPase which undergoes phosphorylation and dephosphorylation, thereby providing energy for transport of these ions against concentration gradients.	ATPase, Sodium, Potassium,Adenosinetriphosphatase, Sodium, Potassium,Na(+)-K(+)-Exchanging ATPase,Na(+)-K(+)-Transporting ATPase,Potassium Pump,Sodium Pump,Sodium, Potassium ATPase,Sodium, Potassium Adenosinetriphosphatase,Sodium-Potassium Pump,Adenosine Triphosphatase, Sodium, Potassium,Na(+) K(+)-Transporting ATPase,Sodium, Potassium Adenosine Triphosphatase,ATPase Sodium, Potassium,ATPase, Sodium-Potassium-Exchanging,Adenosinetriphosphatase Sodium, Potassium,Pump, Potassium,Pump, Sodium,Pump, Sodium-Potassium,Sodium Potassium Exchanging ATPase,Sodium Potassium Pump
D000328	Adult	A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available.	Adults