Studies on the Effect of Vanadate on Endocytosis and Shape Changes in Human Red Blood Cells

When amphipathic cationic drugs are added to intact human RBCs. the RBCs first undergo a stomatocytic shape change and then. if relatively large amounts of drug are added and if the metabolic state of the RBC is appropriate. endocytic vacuoles form. Vanadate has a structural similarity to the transition state of phosphate. which presumably accounts for its ability to inhibit phosphohydrolases. although other actions of vanadate have been described. Vanadate inhibited three forms of drug-induced endocytosis in intact RBCs despite the fact that the three drugs chosen (primaquine. chlorpromazine, and vinblastine) are known to have differing requirements for RBC ATP. Vanadate also inhibited the stomatocytic shape change produced by primaquine, chlorpromazine, and vinblastine, but