Calcium movements associated with peptide induced phagocytosis inAmoeba proteus

Summary Calcium controls the level of phagocytosis inAmoeba proteus which is inhibited by substances such as verapamil and flunarazine which interfere with Ca⁺⁺ movements in a variety of cell systems. Calcium ion movements in amoebae under control conditions appear to be primarily diffusive in response to activity and electrical potential gradients. Chemotactic peptides (n-formylmethionylleucylphenylalanine, NFMLP) at high concentrations (10^–5 M) induce phagocytosis in the amoeba and bring about a concomitant increase in⁴⁵Ca influx. Verapamil, flunarazine and La⁺⁺⁺ all block the increased⁴⁵Ca influx caused by NFMLP, as well as inhibiting phagocytosis. It is suggested that initiation of phagocytosis in the amoeba is associated with the movement of Ca⁺⁺ into the cytoplasm from the external medium resulting in a transient increase in the cytoplasmic Ca⁺⁺ ion activity.