Calcium and initial surface binding phase of pinocytosis in Amoeba proteus
Prusch, R.D.
American Journal of Physiology 251(2 Pt 1): C153-C158
1986
ISSN/ISBN: 0002-9513 PMID: 2426953 Document Number: 272814
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 .apprx. 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 .times. 10-5 to 1.5 .times. 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.