[Purification of an endogenous inhibitor of sodium-potassium-ATPase]

From human plasma of healthy subject, an inhibitor of Na+, K+-ATPase was prepared, using a gel filtration followed by anion exchange chromatography and by HPLC on reverse phase. This low molecular weight (less than 1,500 dalton) inhibitor is a substance which possesses anionic charges, and is absorbed on reverse phase. It inhibits Na+, K+-ATPase activity and the 3H-ouabain binding on human red blood cells.