The surface conductance of red blood cells and platelets is modulated by the cell membrane potential

Abstract

Dielectrophoretic analysis of cell electrical properties via the Clausius–Mossotti model has been widely used to estimate values of the membrane conductance, membrane capacitance and cytoplasm conductivity of cells. However, although the latter two values produced by this method compare well to those acquired by other electrophysiological methods, the membrane conductance is often substantially larger than that acquired by methods such as patch clamp. In this paper, the electrical properties of red blood cells (RBC) are analysed at two conductivities and following membrane‐altering treatments, to develop a mathematical model of membrane conductance. Results suggest that the RBC “membrane conductance” term is primarily dominated by surface conduction, comprising an element related to medium conductivity augmented by conduction in the electrical double layer, which is in turn altered by the cell membrane potential. Validation of the relationship between membrane potential and membrane conductance was performed using platelets, where a similar relationship was observed. This sheds new light on the origin and significance of the membrane conductance term and explains for the first time phenomena of alterations in the parameter counter to changes in membrane potential or cytoplasm conductivity.

Rapid, label-free, contactless measurement of membrane potential in excitable H9c2 cardiomyoblasts using ζ-potential

“…However, a constant value is consistent with observations in other cell types [21,22]. Given the complexity of the electrical properties of double layers and their effects in cells that have been revealed recently [21,22,34], it appears likely that Ξ does remain constant but that the underlying mechanism may be more complex than predicted by equation (1); that said, it is possible that the low conductivity solution may have caused an increase in Ξ which would explain the elevated estimate of V pol . For example, a value of Ξ = 0.18 would be realistic given known values of V m in hypokalaemia, and remains in line with observed values in red blood cells for example [21].…”

On the low‐frequency dispersion observed in dielectrophoresis spectra

“…Although the patch clamp-derived values of G eff are rarely available in the literature, the examination of the predicted values (Table 1) is in-line with expectations from the RBC data obtained above. For example, THP-1 cells exhibited values of G eff TA B L E 1 The best fit parameters and corresponding estimated cell membrane conductance, using the data from Figure 2 and Equation (7). approximately half that of RBCs but showed a further 70% reduction in estimated G eff in THP-1 cells following treatment with the non-specific K + blocker TEA.…”

“…This enabled us to identify a best fit relationship between these variables and Equation (5). We determined τ by fitting Equation (7) to the data.…”

“…However, when this is substituted into Equation (8) with Equation ( 9), it yielded a κ 2 relationship which did not correlate with our observations. However, recent work by Hughes on RBCs [7] suggested that a better model of G eff derived from C-M analysis by DEP was found to be…”

“…Since then, there has been little examination of the constituent components of the C-M factor in physiological or biophysical terms; it instead assumes that the membrane and cytoplasm are homogeneous materials with simple passive electrical properties. This assumption has recently been challenged by a number of papers which collectively sought to define 'the cellular electrome' as the interaction of several bioelectrical phenomena, including the membrane and zeta potentials, as well as relationships between the passive electrical properties of cytoplasm conductivity [6] and membrane conductance [7].…”