Effects of bivalent cations on the initiation of Na-induced pinocytosis inAmoeba proteus

Summary EGTA in moderate concentrations, sufficient to remove all Ca²⁺ from the cell surface, blocks pinocytosis. But in higher concentrations of EGTA, which chelate also Mg²⁺, the pinocytosis reappears and is strongly enhanced. Simultaneous removal of both Ca and Mg ions by EDTA brings about only potentiating effect. Reintroduction of either Ca or Mg separately, demonstrates that Mg²⁺ is a powerful inhibitor of pinocytosis. The influence of chelators on the pinocytosis is attributed respectively to their selective or unspecific influence on both bivalent ions at the cell surface, without affecting the intracellular contraction mechanism.Study supported by the Research Project II. 1 of the Polish Academy of Science.