The nonspecific nature of the vanadate inhibition of rat ileal (NA,K)-ATPase.

Vanadate has been suggested as an intracellular regulator of (Na+ + K+)-ATPase. To test this hypothesis we examined the stimulatory and inhibitory effects of vanadate on 86--Rb efflux and influx (measurements of the activity of the Na-pump) in rat ileum under conditions of normal, reduced and increased (Na+ + K+)-ATPase activity. The half maximal stimulation of the Rb efflux and the half maximal inhibition of the Rb influx were not different in the three conditions tested. This suggests that vanadate does not have a regulatory effect on the activity of the Na-K-transport enzyme. The vanadate effect seem rather, to be nonspecific in terms of being unrelated, on a mole per mole basis, to the activity of the (Na+ + K+)-ATPase enzyme.