Effect of lanthanum on pinocytosis induced by cations in Amoeba proteus.
Lanthanum chloride (greater than or equal to 10(-5) M) induced pinocytosis in normal and at greater than or equal to 10(-4) M in Ca++-deficient amoeba. With respect to the Ca++-requirement of the pinocytotic response low and high concentrations of La+++ had effects like Na+ and K+, respectively. The concentration of La+++ stimulated or inhibited other types of pinocytosis. Thus all concentrations of La+++ inhibited sodium induced pinocytosis while high concentrations (greater than 10(-3) M) stimulated and low concentrations diminished potassium induced pinocytosis. Only the latter effect required the presence of Ca++. In the presence of La+++ other inducers acted either like K+ or Na+. Inducers may cause channel formation by opening a pore for Ca++ in the plasma membrane, Na+ like inducers being less effective than K+-like inducers, and by releasing Ca++ into the cytoplasm from the glycocalyx (Na+-like inducers) or from the entire cell membrane (K+-like inducers). La+++ may diminish the effect of Na+-like inducers and vice versa by direct competition for sites in the glycocalyx and the effect of a K+-like inducer by redistribution of Ca++ in the cell surface. At high concentrations or in the presence of a K+-like inducer La+++ may enter the Ca++ pore, release Ca++ from the interior of the membrane and so induce or stimulate pinocytosis.
D000656:Amoeba / Q000187:drug effects*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004347:Drug Interactions; D004533:Egtazic Acid / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D010873:Pinocytosis / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology
D013096:Spermine; D004533:Egtazic Acid; D007811:Lanthanum; D012964:Sodium; D011188:Potassium; D002118:Calcium