1. Transmembrane Potential of Red Blood Cells Under Low Ionic Strength Conditions
Cell Physiol Biochem 2013;31: DOI: /
Fig. 1. Flow cytometric analysis of DiBAC4(3) fluorescence intensity (arbitrary units) of human RBCs for transmembrane potential over a time interval of 30 min in physiological solution (●) as well as in low ionic strength solution containing 250 mM (■) or 200 mM (▲) sucrose. Error bars (not shown for 200 mM data) represent mean values of at least 5 different blood samples ± SD (with 20,000 cells per sample).
© 2013 S. Karger AG, Basel - CC BY-NC 3.0

2. Transmembrane Potential of Red Blood Cells Under Low Ionic Strength Conditions
Cell Physiol Biochem 2013;31: DOI: /
Fig. 2. Representative calibration curve for human RBCs to convert the fluorescence intensity of DiBAC4(3) into the corresponding transmembrane potential. For each experiment (blood sample) a calibration curve was determined. For details see Materials and Methods section.
© 2013 S. Karger AG, Basel - CC BY-NC 3.0

3. Transmembrane Potential of Red Blood Cells Under Low Ionic Strength Conditions
Cell Physiol Biochem 2013;31: DOI: /
Fig. 3. Calibration curves of CCCP method. 200 µl of freshly drawn packed RBCs were added to unbuffered physiological solution with various concentrations of K+ (from bottom 7.5 mM, 35 mM, 75 mM and 150 mM, respectively) in the presence of 20 µM of the protonophore CCCP and 10 µM of the chloride conductance inhibitor NS1652. Once membrane potential has been stabilized, the ionophore valinomycin was added, leading to hyperpolarization due to K+ efflux, then VM tends eventually to EK+. The membrane potential is plotted against final K+ concentration determined in extracellular solutions by flame photometry (inset, data presented are mean ± SEM of 3 independent experiments).
© 2013 S. Karger AG, Basel - CC BY-NC 3.0

4. Transmembrane Potential of Red Blood Cells Under Low Ionic Strength Conditions
Cell Physiol Biochem 2013;31: DOI: /
Fig. 4. Representative experiment of transmembrane potential estimation of human RBCs in unbuffered solutions in the presence of 20 µM of the protonophore CCCP. At time zero, 200 µl of packed RBCs were added to 4.8 ml HIS (high ionic strength) solution - lower trace, or LIS (low ionic strength) solution - upper trace and the pH measured (right axis). Then it was converted into transmembrane potential (left axis, see Methods). At the end of the experiment Triton X-100 was added to determine the intracellular pH.
© 2013 S. Karger AG, Basel - CC BY-NC 3.0

5. Transmembrane Potential of Red Blood Cells Under Low Ionic Strength Conditions
Cell Physiol Biochem 2013;31: DOI: /
Fig. 5. Representative experiment of transmembrane potential estimation of cow RBCs in unbuffered solutions in the presence of 20 µM of the protonophore CCCP. At time zero, 200 µl of packed RBCs were added to 4.8 ml HIS (high ionic strength) solution - lower trace, or LIS (low ionic strength) solution - upper trace and the pH measured (right axis). Then it was converted into transmembrane potential (left axis, see Methods). At the end of the experiment Triton X-100 was added to determine the intracellular pH.
© 2013 S. Karger AG, Basel - CC BY-NC 3.0