The contractile vacuole of Amoeba proteus. III. Effects of inhibitors

Abstract

The effects of cyanide and malonate have been observed on the fine kinetics of the contractile vacuole of Amoeba proteus. Brief exposure to cyanide does not produce any inhibition of vacuolar output rate. Only after keeping the amoeba in cyanide solution for long periods (9 h) and renewing the inhibitor solution frequently was significant (76%) inhibition of output rate observed. Owing to this reduction in output rate, the volume of the organism doubles in approximately 9 h. Malonate induces mild (30%) inhibition of the vacuolar output. This inhibition normally is alleviated on return to original Chalkley's medium.It is concluded that the vacuolar operation in Amoeba proteus is an energy dependent phenomenon. Such energy can be derived from respiratory or glycolytic processes. However, the congregation of mitochondria around the contractile vacuole suggests that respiratory oxidation may be the chief source of energy supply. The cellular homeostasis is probably maintained through a Na+–K+ pump, operative in the vacuolar membrane.