ATP and the contractile vacuole in <i>Amoeba proteus</i>: Mechanism of action of exogenous ATP and related nucleotides

Abstract

Abstract The mode of action of external ATP on the contractile vacuole of Amoeba proteus has been examined. ATP and, to a lesser extent, some other polyphosphates, interact with calcium at nonhydrolyzing membrane sites. This induces an increase of output of the contractile vacuole provided sodium is present in the medium. A long‐lasting reversible membrane depolarization occurs in the presence of ATP. Results are discussed in the light of theories describing the contractile vacuole as the principal sodium‐excreting organelle in freshwater Protozoa.