Exocytosis of pinocytic contents by Chinese hamster ovary cells.
The extent of exocytosis of pinocytic vesicle contents was studied in suspension-cultured Chinese hamster ovary (CHO) cells using horseradish peroxidase (HRP) as a pinocytic content marker. HRP was shown to be internalized via fluid-phase pinocytosis in CHO cells. After an HRP pulse of 2.5-10 min a rapid decrease of 30-50% in cell-associated HRP activity was observed within 10-20 min at 37 degrees C. During this time the loss of cell-associated HRP was accompanied by an equivalent increase in extracellular HRP. After this rapid exocytosis of HRP, the remaining peroxidase activity decreased with a t1/2 of 6-8 h, the known lysosomal half-life of HRP. In pulse-chase experiments HRP was chased into a nonexocytic compartment. Based on cell fractionation and electron microscopic experiments, this nonexocytic compartment was identified as a lysosome and the compartment from which exocytosis occurs as a pinosome. The occurrence of pinocytic content exocytosis in cultured fibroblasts suggests that exocytosis of pinocytic vesicle contents is a general phenomenon.
D000818:Animals; D002241:Carbohydrates / Q000494:pharmacology; D002458:Cell Fractionation; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D003594:Cytoplasmic Granules / Q000502:physiology*; D005089:Exocytosis; D005260:Female; D005347:Fibroblasts / Q000648:ultrastructure; D006596:Hexosaminidases / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism; D007700:Kinetics; D008247:Lysosomes / Q000502:physiology; D010053:Ovary; D010873:Pinocytosis
D002241:Carbohydrates; D006735:Horseradish Peroxidase; D006596:Hexosaminidases