A quantitative study of pinocytosis and lysosome function in experimentally induced lysosomal storage

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Abstract
The highly pinocytic epithelial cells of the visceral yolk sac from 17.5-day rat conceptuses were used as a model in which to induce engorgement of the vacuolar system by direct accumulation of substances that are not hydrolyzed by lysosomal enzymes. The ultrastructural appearances of these cells in pregnant animals that 24-48 h before had received i.p. injection of Triton WR-1339, polyvinylpyrrolidone, dextran or sucrose revealed gross abnormalities that were confined to the vacuolar system; in comparison with normal tissue the number, and in some cases the size, of vacuoles was increased, leading to close packing within the apical cytoplasm and distortion of the normal rounded shape. By culturing yolk sacs in vitro, rates of ingestion of 125I-labeled polyvinylpyrrolidone and of 125I-labeled bovine serum albumin were determined, together with the rate of digestion of the labeled protein. The rates of exocytosis of 125I-labeled polyvinylpyrrolidone and of lysosomal enzymes were also determined. No significant differences between normal and highly vacuolated tissues were found. Apparently marked vacuolation of these cells by these agents is without significant effect on pinocytosis, exocytosis or intralysosomal proteolysis.