Utilization of Liquid Ion Exchanger Microelectrodes to the Cell of the Biological Membrane

Measurement of Intracellular Electrolytes and its Estimation

Abstract

To determine the intracellular ion activities of potassium and chloride, the present study was aimed to make potassium sensitive and chloride sensitive liquid ion exchanger microelectrodes (K⁺-microelectrode and Cl^--microelectrode, respectively), and to measure the intracellular K⁺ and Cl^-activities in the toad urinary bladder epithelial cells.
The characteristics of K⁺- and Cl^--microelectrodes were examined. The sensitivity slope (sRT/zF In 10) and the standard potential of the K⁺-microelectrode was 59.04±0.03mV/10 fold of ionic activity and 22.2±0.69mV, respectively. The slope and the standard potential of the Cl^--microelectrode was-58.38±0.19 and-42.23±0.90, respectively. The selectivity constant of the K⁺-mircoelectrode was 53.96±4.00 for K⁺/Na⁺ and 3.48±0.15 for K⁺/NH₄⁺. In addition, that of Cl^-- microelectrode was 8.00±0.15 for Cl^-/HCO₃^- and 63.59±1.20 for Cl^-/H₂PO₄^-.
It was suggested that K⁺- and Cl^--microelectrodes could be available for determination of the intracellular K⁺- and Cl^- activities in a biological membrane.
The present authors attempted to determine the intracellular K' and Cr activities in the toad urinary bladder epithelial cells, and to investigate the different forms of these ions in the cells and their transport mechanisms.
The intracellular concentration of free potassium ion could be calculated to be 54.2mM from the obtained aⁱ_K, 41.2mM, and that of free chloride could be calculated to be 65.7mM from the obtaineda aⁱ_K, 49.9mM undert he basalc onditions. By the method of the chemical analysis, the intracellular concentrations of potassium and chloride were reported about 130 mMand 62mM, respectively. So, it was suggested that about one half of the intracellular potassium might be free and another half might be bound or sequestrated, and that the intracellular chloride might be almost free.
Furthermore, it was suggested that potassium ion might be actively intaked into the cell from the serosal medium, probably Na-K exchange system, and that the mechanism of the chloride absorption could not need the active process.