Counter-ion polarization and low frequency, low electric field intensity biological effects

Abstract

By analysis of published experimental data for the dielectric properties of tissue at extremely low frequencies it is shown that the “thermal noise problem” is much less severe for field effects depending on counter-ion polarization than for effects that require a change of transmembrane potential. Application of dielectric mixture theory and the theory of counter-ion polarization is used to show that the fraction of charges near the cell surface involved in counter-ion polarization is of the order of 10−6 at the thermal noise limit when the frequency of the applied field is 15 Hz. It is also shown that the exponential decay distance for polarization-related charge motion can be more than 50% of the intercell spacing. Thus extremely low frequency electric fields that cause counter-ion polarization can affect the ionic environment of those membrane-embedded proteins which extend far into the intercellular medium and can possibly also influence cell-to-cell communication.