title: Involvement of Na+ and HCO-3 in receptor-mediated endocytosis of alpha 2-macroglobulin, epidermal growth factor, and vesicular stomatitis virus.
abstract: alpha 2-Macroglobulin (alpha 2M), epidermal growth factor (EGF), and vesicular stomatitis virus (VSV) each enter cultured fibroblasts by receptor-mediated endocytosis. The present study defines some basic ionic requirements in the cell culture medium which are necessary for the maximal rate of endocytosis of these three ligands. Na+ and HCO-3 were both necessary for maximal endocytosis of 125I-alpha 2M, 125I-EGF, and 35S-VSV at 37 degrees C. The ion specificities for both the anion and cation requirements were established. The binding of 125I-alpha 2M to its cellular receptors at 4 degrees C was unaffected by the absence of Na+ and HCO-3 in the culture medium. In addition, the absence of Na+ and HCO-3 in the culture medium did not reduce cellular uptake of horseradish peroxidase by fluid phase endocytosis. Na+ and HCO-3 may be general requirements in receptor-mediated endocytosis.
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002478:Cells, Cultured; D004705:Endocytosis; D004815:Epidermal Growth Factor / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism; D006801:Humans; D051379:Mice; D012964:Sodium / Q000494:pharmacology*; D014721:Vesicular stomatitis Indiana virus / Q000502:physiology*; D000511:alpha-Macroglobulins / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D000511:alpha-Macroglobulins; D004815:Epidermal Growth Factor; D012964:Sodium; D006735:Horseradish Peroxidase