The Influence of Intracellular Vesicle Size and Position on the Transmembrane Voltage Induced by Nanosecond Electric Fields

Abstract

Recent reports show that nanosecond electric pulses of sufficient magnitude impact on intracellular structures of biological cells. The effects that occur are correlated with the change in the potential difference on the membranes induced by the applied electric field – the induced transmembrane voltage (ITV). We constructed a finite element model of a cell containing a larger organelle (nucleus) and several vesicles of two sizes; with radii of 500 nm and 50 nm. We calculated the response to a single 50 ns, 5 kV/cm pulse and investigated the influence of size and position of intracellular vesicles on the transmembrane voltage induced on the cell membrane, nuclear membrane and vesicle membranes. The results show that the nucleus influences the time course and the amplitude of the ITV on a vesicle if it is positioned close to the nucleus, while the influence is negligible if the vesicle is positioned far from the nucleus. The maximum ITV on vesicles compared to ITV on the nuclear and cell membrane is at least three times lower for 500 nm vesicles and more than thirty times lower for 50 nm vesicles. We also demonstrated that the time course and the amplitude of the ITV on the cell membrane, nuclear membrane or the vesicle depend on the electrical parameters of the model and can be quite different just by setting one of the parameters to a somewhat different value. For example, if the cytoplasmic conductivity is moderately reduced, the ITV on the 500 nm vesicle can be higher than the ITV on the membrane, regardless of the vesicle position. This indicates that if electric parameters used in numerical modeling do not match their realistic counterparts the predictions of the model can be markedly different from the experimental results.