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Measurement of the Electrical Potential Difference and the Distribution of Ions in the Shay Chloroleukemic Tumor Cell¹

Department of Biological Sciences, Hunter College, City University of New York [A. E. S., E. E. H., E. S. H.], and the Department of Physiology, Cornell University Medical College [H. G. H.], New York, New York 10021

The electrolyte pattern and the potential difference (PD) across the membrane of the Shay chloroleukemic tumor cell was examined. The potassium ion concentration was 122 ± 9 mEq/liter of cell water; sodium was 48 ± 4 mEq/liter; chloride was 72 ± 7 mEq/liter; and water was 77.5% ± 0.5% of cell wet weight. The average PD was 9.2 ± 0.4 mV, inside negative to ground potential outside. Raising the external potassium concentration from 7 to 120 mEq/liter by replacement of external sodium did not change the internal potassium concentration significantly after equilibration for 1 hr at 23°; the PD was reduced by 2 mV. Replacement of chloride ion with sulfate reduced intracellular chloride significantly and depolarized the membrane to zero. However, the Nernst equilibrium potential for chloride ion in normal Ringer's medium was -21.3 mV, more negative than the measured values. Since the steady-state flux of sodium ion exceeded that for chloride ion, sodium may contribute to the deviation of the measured PD from a true chloride equilibrium potential by providing a low-resistance shunt.

¹ Supported by Grant NSF 17,679 from the National Science Foundation [E. E. H.] and by Grants CA 07977-06 [E. S. H.] and CA 03690-14 [H. G. H.] from the USPHS.

² Present address: Department of Physiology, Medical University of South Carolina, Charleston, S. C. 29401.

Received 7/26/71. Accepted 3/ 6/72.