Effects of temperature, potassium, and calcium on the electrical potential difference in HeLa cells.

The electrical potential difference (P.D.) across the cell membrane was measured in monolayers of HeLa cells. At 37°C in the cells' growth medium, the mean P.D. was found to be —1 5.45 ±0.57 my, the cell interior being negative. In Tris buffer the P.D. was —17.10 ±0.71 my. The PD. was tempera ture sensitive, falling to —11.9 my at 27°Cand —9.12my at 17°C.Increasing extracellular K decreased the P.D. with a slope suggesting a very high relative permeability to sodium. The @ calculated from the Goldman-Hodgkin-Katz equa tion was found to be 0.57. It is proposed that a high Na permeability relative to K may be characteristic of cells with a high aerobic glycolytic activity. The P.D. was not affected by high external Ca but fell from —17.1 to 7.14 my in Ca-free media, suggesting a further increase in the Na to K permeabil ity ratio.