The effects of a low extracellular concentration of potassium on the activity and numbers of Na+/K+ pumps in an EB-virus transformed human lymphocyte cell line.

The BM1A EB-virus transformed human lymphocyte cell line contains approximately 950,000 Na+/K(+)-ATPase sites per cell. The turnover number of each site is approx. 2240 molecules of rubidium per min. When cells are exposed to a low extracellular concentration of potassium the intracellular concentration of sodium rises, and the cells respond in the short term by increasing the Vmax of 86Rb+ uptake. In the longer term the cells respond by increasing both the Vmax of 86Rb+ uptake and the Bmax of [3H]ouabain binding. The suggestion that increases in the intracellular concentration of sodium is responsible for these changes is supported by the finding that monensin, which increases intracellular sodium without affecting intracellular potassium, is capable of inducing both the short- and long-term changes associated with a low external concentration of potassium.