title: Calcium and initial surface binding phase of pinocytosis in Amoeba proteus.
abstract: The uptake of membrane-bound solute and external medium by bulk-phase pinocytosis in Amoeba proteus is influenced by the level of Ca2+ in the external medium. Increasing external Ca2+ to approximately 10(-4) M increases pinocytotic intensity, while increases in Ca2+ above this level decrease the intensity of pinocytosis. The initial interaction of pinocytotic inducers and Ca2+ at the surface of Amoeba proteus was therefore examined. Alcian blue and Na+, both inducers of pinocytosis, differ in the manner with which they associate with the amoeba surface, suggesting the possibility of different pinocytosis-inducing sites on the amoeba surface. Low levels of external Ca2+ in the range of 3 X 10(-5) to 1.5 X 10(-4) M increase the amount of cationic inducer associated with the cell surface while, at the same time, decreasing anion association with the cell surface. It is suggested that Ca2+ influences ion association with the cell surface by controlling the availability of negative surface sites, which in turn influences pinocytotic intensity.
mesh_terms: D000423:Alcian Blue / Q000494:pharmacology; D000656:Amoeba / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D003470:Culture Media; D007473:Ion Channels / Q000502:physiology*; D010873:Pinocytosis / Q000187:drug effects; D012964:Sodium / Q000494:pharmacology
chemical_list: D003470:Culture Media; D007473:Ion Channels; D012964:Sodium; D000423:Alcian Blue; D002118:Calcium