Abstract
An unique endogenous digitalis-like factor (EDLF) has been previously purified from human newborn cord plasma and its differential effects tested on the three well defined functional isoforms (alpha1, alpha2 and alpha3) of the alpha subunits of Na+/K+-ATPase in rat. EDLF specifically inhibits the enzymatic activity. It differs from ouabain by three criteria: a preincubation with the membranes is required for full activity, no effect on the rat cerebral alpha3 isoform and a steep dose-response curve with the same apparent potency for rat alpha2 and alpha1 isoforms of high (10(-7) M) and low affinity (3 x 10(-5) M) for ouabain. These results indicate that the Na+/K+-ATPase inhibitor involved in the regulation of sodium and body fluid volume and present in neonate and adult human plasmas is distinct from ouabain.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Brain / enzymology
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Cardenolides
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Cell Membrane / enzymology
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Digoxin*
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Dose-Response Relationship, Drug
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Enzyme Inhibitors / blood
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Enzyme Inhibitors / isolation & purification
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Enzyme Inhibitors / pharmacology*
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Humans
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Infant, Newborn
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Isoenzymes / antagonists & inhibitors*
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Isoenzymes / metabolism
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Kidney / enzymology
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Myocardium / enzymology
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Ouabain / pharmacology
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Plasma Volume / drug effects
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Plasma Volume / physiology
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Rats
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Rats, Wistar
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Saponins / blood
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Saponins / isolation & purification
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Saponins / pharmacology*
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Sodium / metabolism
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Sodium-Potassium-Exchanging ATPase / antagonists & inhibitors*
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Sodium-Potassium-Exchanging ATPase / metabolism
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Spectrophotometry
Substances
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Cardenolides
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Enzyme Inhibitors
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Isoenzymes
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Saponins
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digoxin-like factors
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Ouabain
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Digoxin
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Sodium
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Sodium-Potassium-Exchanging ATPase