Intracellular K +, Na + and Cl − concentrations and membrane potential in human moncytes

Abstract

The relationship between the resting membrane potential and the intracellular ionic concentrations in human monocytes was investigated. Cell volume, cell water content, and amount of intracellular K +, Na +, and Cl − were measured to determien the intracellular concentrations of K + (K i), Na + (Na i) and Cl − (Cl i) of monocytes, and of lymphocytes and neutrophils. Values found for monocytes were similar to those for neutrophils, i.e., cell volumes were 346 and 345 μm 3, respectively, cell water content78%, and K i, 128 and 125, Na i, 24 and 26, and Cl i, 102 and 103 mmol/l cell water, respectively. Lymphocytes, however, had different values: 181 μm 3 cell volume, 77% cell water content, and for K i, Na i, and Cl i, 165, 37, and 91 mmol/l cel water, respectively. The resting membrane potential of cultured human monocytes (range -30 to -40 mV), determined by measurement of the peak potential occurring within the first milliseconds after microelectrode entry, was most dependent on extracellular K +, followed by Cl −, and Na +. The membrane permeability ratio of Cl − to K + was estimated by use of the constant field equation to be 0.23 (range 0.22 to 0.30).