Effects of Lanthanum on Pinocytosis Induced by Cations in Amoeba proteus

Abstract

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.

Induction and inhibition of pinocytosis by aminoglycoside antibiotics

“…ent cations. In both this respect and in its inhibition by Na+ it resembled pinocytosis induced by La3+ (Josefsson & Hansson, 1976). Thus, the intense pinocytotic activity exhibited by cells in media containing 160MM netilmicin was reduced by 90% in the presence of 16 mM NaCl.…”

“…Compared to pinocytosis induced by monovalent cations that induced by the aminoglycosides was less inhibited by Ca2 . In this respect and in their inhibition of Na+-induced pinocytosis the antibiotics resembled La3+ (Josefsson & Hansson, 1976). Furthermore, pinocytosis induced by the antibiotics, like that induced by La3+, was inhibited by Na+.…”

“…We investigated carbenicillin, which inhibited pinocytosis induced by the aminoglycosides but not that induced by other cations (Na+, K+, lysozyme). The effect of the interaction between 1 mgmlcarbenicillin and neomycin is shown in (Josefsson & Hansson, 1976). Thus, the intense pinocytotic activity exhibited by cells in media containing 160MM netilmicin was reduced by 90% in the presence of 16 mM NaCl.…”