External potassium and baby hamster kidney cells: Intracellular ions, ATP, growth, DNA synthesis and membrane potential

Abstract

The relationship between cell multiplication, DNA synthesis and external potassium concentration has been investigated in baby hamster kidney (BHK) cells. Alterations in the rate of 3H-thymidine incorporation were paralleled by changes in the rate of growth. The optimal external potassium concentration was 64 m M and either an increase or decrease from this level was inhibitory. Changes in 3H-thymidine incorporation with the various potassium media appeared to be immediate (5 min pulse). Intracellular sodium and potassium concentrations measured at 5 min, 2 hr, and 24 hr at various external potassium concentrations indicated that the changes in 3H-thymidine incorporation were not related to changing intracellular ion levels. The ATP content of potassium-inhibited cells was not significantly different than control cells. The membrane potential was primarily dependent on the potassium distribution and could be manipulated by changing the ratio of external to internal potassium. The relationship between membrane potential and 3H-thymidine was explored by varying the external potassium concentration from 1.75 to 121 m M. To distinguish between the effects of external potassium per se and the membrane potential, 3H-thymidine incorporation was measured at 5 or 93 m M external potassium in normal and potassium-depleted cells. The results raise the possibility that the cell membrane potential may influence DNA synthesis.