The action of phloridzin and sugars on (Na(+)-K (+))-Activated ATPase.

The action of phloridzin and simple sugars on the (Na(+)-K(+))-activated ATPase obtained from rabbit kidney has been studied. Phloridzin 10(-4)to 10(-3) M was found to inhibit the enzyme at Na(+):K(+) ratios less than optimal for enzyme activity, whereas stimulation was noted at Na(+):K(+) ratios greater than optimal for enzyme activity. Some sugars in concentrations of 0.1 to 0.5M were found to inhibit the (Na(+)-K(+))-activated ATPase. The sugars and related compounds could be ranked according to decreasing inhibitory potency as: D-mannose>D-arabinose, D-xylose>L-xylose>D-glucose>fructose, L-arabinose>D-galactose, myo-inositol, mannitol=0. No stimulatory effect or interaction with K(+) was found with these compounds. The action of these substances on the (Na(+)-K(+))-activated ATPase suggests an interaction of actively transported sugars and sodium-potassium transport at the level of the sodium pump that may be important in the biological coupling of the two systems.