title: Energized endocytosis in human erythrocyte ghosts.
abstract: The mechanism of endocytosis in resealed human erythrocyte ghosts was studied. The energy for endocytosis or micropinocytosis appears to be derived from Mg-ATP, and membrane internalization is preceded by activation of a membrane-associated Ca,Mg-ATPase and by the active efflux of Ca. Endocytosis, Ca,Mg-ATPase activity, and active Ca efflux all require the presence of Mg. Furthermore, these three phenomena, endocytosis, Ca,Mg-ATPase activity, and active Ca extrusion, all have a concentration dependence on Ca such that low concentrations stimulate and higher concentrations inhibit the phenomena. The optimal concentration of Ca is identical for endocytosis, active Ca efflux, and Ca,Mg-ATPase. Morphologic studies indicated that while active Ca efflux and activation of the Ca,Mg-ATPase activity occurred promptly upon onset of incubation, there was a significant time delay before endocytosis occurred, which suggests that endocytosis additionally involved a more slowly functioning mechanicochemical mechanism. Ruthenium red, a specific inhibitor of Ca,Mg-ATPase and Ca transport, inhibited endocytosis in a concentration-related manner. Prostaglandins E1 and E2 had no measurable effect on ghost endocytosis, active Ca efflux, or Ca,Mg-ATPase activity.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D002463:Cell Membrane Permeability; D004705:Endocytosis; D004912:Erythrocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D006454:Hemoglobins; D006461:Hemolysis; D006801:Humans; D066298:In Vitro Techniques; D008274:Magnesium / Q000378:metabolism; D008854:Microscopy, Electron; D010587:Phagocytosis; D010761:Phosphorus Radioisotopes; D010873:Pinocytosis; D012430:Ruthenium Red / Q000494:pharmacology; D013054:Spectrophotometry, Atomic; D013997:Time Factors
chemical_list: D002132:Calcium Radioisotopes; D006454:Hemoglobins; D010761:Phosphorus Radioisotopes; D012430:Ruthenium Red; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium