Effect of magnesium-dependent cell membrane alterations on the transport of K+ in Ehrlich ascites tumour cells.
Mg-deficiency or Mg-loading of tumour cells changes the permeability of the cell membrane. The influence of this change on the K+ transport across the membrane was investigated using 86Rb+ and K+ analog. The time course of the influx and efflux rates were estimated by means of a mathematical approach for a two-compartment system with inconstant pool sizes. The comparison of the two states of the cells demonstrates that in Mg-deficient cells the passive K+ efflux is significantly enhanced (40%). This in turn stimulates the active counter transport mediated by the (Na+-K+)-ATPase, raising the ATP consumption by about 30%. However, the enzyme is not able to maintain the cellular K+ content under these conditions. After a short transient increase due to the initially enhanced influx the passive net efflux prevails. Differences in the electrophoretic mobility of the two states of the cells confirm Mg-dependent changes of the cell membrane structure.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002478:Cells, Cultured; D008274:Magnesium / Q000494:pharmacology*; D051379:Mice; D011188:Potassium / Q000378:metabolism*; D011868:Radioisotopes; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D011868:Radioisotopes; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D012413:Rubidium; D011188:Potassium