A quantitative study of pinocytosis and intracellular proteolysis in rat peritoneal macrophages

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Abstract
A method for the culture of rat peritoneal macrophages in vitro is described, in which pinocytic uptake of colloidal 198 Au, 125I-labeled poly(vinylpyrrolidone) and [14C]sucrose proceeds at constant and fairly reproducible rates for several hours. The rate of uptake of colloidal 198Au, which exhibited some inter-batch variation, was approximately 100 times that of the other 2 substrates. Colloidal Au did not affect the rate of uptake of 125I-labeled poly(vinylpyrrolidone) and therefore its own high rate of uptake could no be attributed to a stimulation of the formation of pinocytic vesicles. Uptake of colloidal Au is apparently highly dependent on absorption on binding sites on the plasma membrane. Uptake of formaldehyde-treated 125I-labeled bovine serum albumin was followed by the release of [125I]iodo-L-tyrosine into the culture medium and took place at a rate intermediate between those of colloidal 198Au and the other 2 non-digestible substrates, 125I-labeled poly(vinylpyrrolidone) and [14C]sucrose.