Ca2+ translocation in Ehrlich ascites tumor cells.
Ca2+ uptake into Ehrlich ascites tumor cells was studied at 0 degrees C in the presence of mitochondrial inhibitors, conditions that minimized complications caused by sequestration of Ca2+ into organelles or by excretion. Under these conditions Ruthenium Red inhibited Ca2+ uptake, but other previously implicated ions, such as Pi or Mg2+, had no effect. Valinomycin either inhibited or slightly stimulated Ca2+ uptake depending on the presence of excess K+ on the outside or inside of the cell, respectively. Nigericin inhibited Ca2+ transport. Based on these data we propose an electrogenic uptake of Ca2+, possibly via a Ca2+/H+ antiport mechanism. The observation that glucose inhibited Ca2+ uptake suggested that in Ehrlich ascites tumor cells an energy-driven Ca2+ expulsion mechanism is operative, similar to that in erythrocytes. Plasma membrane preparations of ascites tumor cells were found to contain a Ca2+-dependent ATPase. These preparations, when incorporated into liposomes in an inside-out orientation, catalyzed an ATP-dependent uptake of Ca2+.
D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism* / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D008081:Liposomes / Q000378:metabolism; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology
D008081:Liposomes; D010710:Phosphates; D000252:Calcium-Transporting ATPases; D002118:Calcium