| Abstract |
Transmembrane ion transport under tonicity imbalance has been investigated using a combination of low frequency-electrical impedance spectroscopy (LF-EIS) and improved ion transport model, by considering the cell diameterd[m] and the initial intracellular ion concentrationcin[mM] as a function of tonicity expressed by sucrose concentrationcs[mM]. The transmembrane ion transport is influenced by extracellular tonicity conditions, leading to a facilitation/inhibition of ion passage through the cell membrane. The transmembrane transport coefficientP[m s-1], which represents the ability of transmembrane ion transport, is calculated by the extracellular ion concentrations obtained by improved ion transport model and LF-EIS measurement.Pis calculated as 4.11 × 10-6and 3.44 × 10-6m s-1atcsof 10 and 30 mM representing hypotonic condition, 2.44 × 10-6m s-1atcsof 50 mM representing isotonic condition, and 3.68 × 10-6, 5.16 × 10-6, 9.51 × 10-6, and 14.89 × 10-6m s-1atcsof 75, 100, 125 and 150 mM representing hypertonic condition. The LF-EIS results indicate that the transmembrane ion transport is promoted under hypertonic and hypotonic conditions compared to isotonic condition. To verify the LF-EIS results, fluorescence intensityF[-] of extracellular potassium ions is observed to obtain the temporal distribution of average potassium ion concentration within the region of 3.6μm from cell membrane interfacecROI[mM]. The slopes of ∆cROI/cROI1to timetare 0.0003, 0.0002, and 0.0006 under hypotonic, isotonic, and hypertonic conditions, wherecROI1denotes initialcROI, which shows the same tendency with LF-EIS result that is verified by the potassium ion fluorescence observation.
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