Dog kidney (Na+,K+)-ATPase is more sensitive to inhibition by vanadate than human red cell (Na+,K+)-ATPase

(Na+,K+)-ATPase (EC 3.6.1.3) from kidney is more sensitive to inhibition by vanadate than red cell (Na+,K+)-ATPase. The difference appears to be in the apparent affinities of the two enzymes for K+ and Na+ at sites where K+ promotes and Na+ opposes vanadate binding. As a result of Na+-K+ competition at these sites, reversal of vanadate inhibition was accomplished at lower Na+ concentrations in red cell than in kidney (NA+,K+)-ATPase. It is possible that vanadate could selectively regulate Na+ transport in the kidney.