Cl-, Na+, and H+ fluxes during the acidification of rabbit reticulocyte endocytic vesicles.
The ionic fluxes associated with the ATP-dependent acidification of endocytic vesicles were studied in a preparation isolated from rabbit reticulocytes enriched for transferrin-transferrin receptor complexes. No vesicle acidification was observed in the absence of intra- and extravesicular ions (sucrose(in)/sucrose(out), while maximal acidification was observed with NaCl(in)/KCl(out).K+(in) was a poor substitute for Na+(in), and Cl-(out) could be replaced by other anions with the following efficacy of acidification: Cl- greater than Br- greater than I- greater than PO4(3-) greater than gluconate greater than SO4(2-). Flux studies using 36Cl- and 22Na+ showed that the vesicles had a permeability for Cl- and Na+, and that ATP-dependent H+ pumping was accompanied by a net influx of Cl- and a net efflux of Na+ provided that there was a Na+ concentration gradient. After 3 mins, the time necessary to maximal acidification, the electrical charge generated by the entrance of H+ was countered to about 45% by the Cl- influx and to about 42% by the Na+ efflux. These studies demonstrated that both Cl- and Na+ fluxes are necessary for optimal endocytic vesicle acidification.
Gaete
V
V
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago.
Núñez
M T
MT
Glass
J
J
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism*; D004563:Electrochemistry; D004705:Endocytosis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011522:Protons; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D011522:Protons; D000255:Adenosine Triphosphate; D012964:Sodium; D000251:Adenosine Triphosphatases