Oxygen Uptake during Pinocytosis in Amoeba Proteus

The oxygen uptake of Amoeba proteus was measured by the Cartesian ampulla diver technique. The intensity of pinocytosis was determined by counting the number of channels developed during the first 20 min of the pinocytosis induced by potassium chloride. Addition of calcium ions was used to inhibit pinocytosis induced by Tris. The oxygen uptake of the amoeba in culture medium was found to be 2.5 ± 0.9 μl/hr/cell at 25° C. Transient increases in rate of oxygen uptake were observed with different salt solutions. The intensity of respiratory stimulation varied in proportion to the activity of the salt as a pinocytosis inducer. Inhibition of Tris‐induced pinocytosis by calcium and potentiation of potassium‐pinocytosis by lanthanum decreased and respectively increased the respiratory rate of the amoeba. The time course of the development of channels was similar to that of th stimulated oxygen uptake. From experiments with a calcium‐binding agent (EGTA) it was concluded that respiratory stimulation secondary to the increase of the permeability of the cell‐membrane during pinocytosis might add to the energy expenditure during the formation of channels. As with the pinocytosis phenomenon calcium exhibited a dual action on the stimulated oxygen uptake: A minimal concentration was necessary for both processes while addition of calcium inhibited respiratory stimulation as well as pinocytosis.