Vanadate is a potent (Na,K)-ATPase inhibitor found in ATP derived from muscle

A potent (Na,K)-ATPase inhibitor purified from "Sigma Grade* ATP has been identified as vanadium using electron probe microanalysis and confirmed by microwave-induced emission spectroscopy and electron paramagnetic resonance spectroscopy. Sodium orthovanadate (Na3 VO4) is identical with the purified inhibitor with respect to ultraviolet absorbance, migration on thin layer chromatography, and inhibition of (Na,K)-ATPase. The (Na,K)-ATPase is in-inhibited 50% by 40 nM Na3 VO4 under optimal conditions (28 mM Mg2+) and the inhibition is 100% reversible by millimolar concentrations of norepinephrine. The physiological significance of this inhibition is discussed in relation to vanadium concentrations in vivo.