Summary
Under optimum conditions for vanadate binding to Na, K-ATPase equilibrium binding data for a range of vanadate concentrations were compiled. Scatchard plots indicated an identical binding capacity for vanadate and ouabain with conventionally prepared Na, K-ATPase batches. A method for determination of vanadate in serum based upon the high affinity of vanadate for Na, K-ATPase is described. The method takes advantage of the shift in equilibrium binding of (48V) vanadate upon addition of an aliquot of vanadate-containing serum. It is shown that the interplay between vanadate and ouabain in vanadate-facilitated oubain binding to Na, K-ATPase leads to an enzyme-vanadate-ouabain complex to which vanadate is rather firmly bound.
Zusammenfassung
Die [48V]Vanadatbindung an die (Na++K+)-ATPase wurde unter Äquilibriumbedingungen und bei optimalen Inkubationsbedingungen gemessen. Scatchard-Analysen der Vanadatbindung ergeben eine identische Bindungskapazität für Vanadat und Ouabain (g-Strophanthin) in angereicherten (Na++K+)-ATPase-Präparationen. Mit Hilfe dieser hochaffinen Vanadatbindung an die (Na++K+)-ATPase ist eine Bestimmungsmethode für Vanadat im Serum möglich, die sich das Prinzip des „Radiorezeptor-Assays” zunutze macht. Außerdem wird experimentell nachgewiesen, daß die [3H]Ouabain-Bindung an die (Na++K+)-ATPase in Gegenwart von Vanadat zu einem Enzym-Vanadat-Ouabain-Komplex führt, in dem Vanadat relativ fest gebunden wird.
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References
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Hansen, O. Vanadate interaction with the Na, K-ATPase an assay of serum vanadate based on the displacement of (48V) vanadate from Na, K-ATPase. Basic Res Cardiol 75, 455–459 (1980). https://doi.org/10.1007/BF01908411
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DOI: https://doi.org/10.1007/BF01908411