Ref ID : 956
Blair Bowers and Thomas E. Olszewski; Pinocytosis in Acanthamoeba castellanii Kinetics and Morphology. J.Cell Biology 53:681-694, 1972
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The uptake of radioactively labeled albumin, inulin, leucine, and glucose by Acanthamoeba castellanii (Neff strain) was measured. The uptake is linear with time and appears to be continuous under the conditions of these experiments. Uptake is abolished at 0 degrees C. No evidence for saturation of the uptake mechanism was obtained with either albumin or luecine. Each of the four tracer molecules enters the amoeba at a similar rate when the uptake is calculated as volume of fluid ingested per unit time. The data suggest that each of these molecules enters the cell by pinocytosis. The highest rate of uptake was obtained with cells in their usual culture medium containing proteose peptone, glucose, and salts but pinocytosis also continued at a reduced rate in a simple salt solution. The calculated volume of fluid taken in during pinocytosis in culture medium was about 2 ul/hr per 10E6 cells. The route of uptake was examined in the electron microscope using horseradish peroxidase (HRP) as a tracer. HRP activity was found exclusively within membrane profiles within the cytoplasm, confirming the pinocytosis was made using the biochemical and morphological data obtained. This estimate suggests that the plasma membrane turnover of one cell is on the order of several times an hour.