Electrical properties of Ehrlich ascites tumor cells

Abstract

The cell membrane potential (PD) of Ehrlich ascites tumor cells was measured continuously at 37 degrees C with conventional microelectrodes during rapid alterations of extracellular fluid composition. At extracellular electrolyte composition mimicking the in vivo situation PD is -56.7 +/- 0.7 mV and the apparent membrane resistance is 62.2 +/- 2.2 M omega. Increasing extracellular potassium concentration from 5.4 to 20.0 mmol/l depolarizes the cell membrane by +18.4 +/- 0.5 mV. Thus, the transference number for potassium (tk, apparent slope potassium conductance over slope membrane conductance) is 0.53 +/- 0.01. A significant correlation is observed between tk and PD: tk = -(0.014 +/- 0.001) [1/mV] X PD [mV] -(0.243 +/- 0.051). 0.7 mmol/l barium depolarizes the cell membrane by +28.2 +/- 0.7 mV, increases the apparent membrane resistance by a factor of 2.6 +/- 0.1 and abolishes the apparent potassium conductance. Reduction of extracellular sodium concentration from 141 to 21 mmol/l depolarizes the cell membrane by +3.1 +/- 1.3 mV. Similarly, 0.1 mmol/l amiloride depolarizes the cell membrane by +3.3 +/- 0.7 mV. Reduction of extracellular chloride concentration from 128 to 67 mmol/l hyperpolarizes the cell membrane by -2.5 +/- 0.2 mV. 1 mmol/l anthracene-9-COOH does not significantly alter PD. Temporary omission of glucose from the extracellular fluid has no appreciable effect on PD. In conclusion, PD of Ehrlich ascites tumor cells is in the range of other mammalian epithelial cells and is generated mainly by potassium diffusion, while the conductances to sodium and chloride appear to be small.

Membrane potential, anion and cation conductances in Ehrlich ascites tumor cell

“…4) and we have estimated the resulting hyperpolarization caused by the dye to be less than 2 mV, assuming that the C1-conductance in unpertubated cells is comparable to the C1-conductance in pertubated cells. The corrected membrane potential of -61 mV (see Table 1) is in accordance with the -56.7 mV measured in Ehrlich cells by a conventional microelectrode by Gstrein et al (1987). It should be noted that if only 40% of cellular K + should behave as if it was in free solution, as proposed by Dawson and Smith (1986), the dye method used in the present report would overestimate the true value by 15.5 mV, resulting in a membrane potential of -45.5 mV, which is significantly lower than the value measured by Gstrein et al (1987).…”

“…In conclusion, Ehrlich ascites tumor cells have a membrane potential in the range of -56 to -61 mV, as estimated by conventional microelectrodes (Gstrein et al, 1987), or by the modified fluorescence method described in the present paper. Previously estimation of the membrane potential from our laboratory are probably all underestimated either due to leakage caused by the microelectrode impalement (Hoffmann et al, 1979) or from misinterpretation of the valinomycin "null point" (Hoffmann & Lambert, 1983).…”

“…In the Ehrlich ascites tumor cell, the current through the plasma membrane is carried mainly by K ), Na' and CI , while any electrogenic contribution of the Na +/K ~ pump seems to be negligible (see Gstrein et al, 1987). Accordingly, under steadystate conditions with constant potentials, i.e., where the total current across the membrane is zero we get GK -(V,,, -EK) + GNa" (V,, --EN,,)…”

“…Blocking the K + channels in a Na+-free medium either by addition of quinine (Figs. 8 and 9) or by addition of Ba 2+ (Gstrein et al, 1987) produces a strong depolarization of the membrane potential. Since Na + has no influence on the membrane potential in nominantly Na+-free medium, and EK is more negative than the membrane potential (see Table 1), such depolarization can only be explained ifEc~ is less negative than Vm.…”

pH distributions in spontaneous and isotransplanted rat tumours

“…The interior of tumour cells is generally found to be electronegative as compared to the extracellular space. The transmembrane potential varies between -9 and -57 mV with most values found in the range of -10 to -25mV (Bernhardt & Pauly, 1967;Borle & Loveday, 1968;Hause et al, 1970;Timmermann & von Buttlar, 1978;Walliser & Redmann, 1978;Redmann, 1981;Acker et al, 1983;Gstrein et al, 1987). Since the possibility of proper intracellular pH measurements can be ruled out due to the electrode size, the membrane potential of tumour cells is unlikely to influence significantly the pH values measured in the present study.…”