Ionic modulation of electrically induced fusion of mammalian cells.

During the last few years, a new technique has been developed for the "electrofusion" of mammalian cells. No previous treatment of the culture is needed, for the contact between cells is spontaneous. Short DC electric pulses are applied directly to a culture growing in monolayers on a culture dish. When the cell density is high enough, contacts occur between cells giving the so-called contact inhibition. In the present study, a systematic investigation of the modulation of the extent of the fusion by the ionic content of the bathing medium during the pulsation is described. An increase in the content in monovalent ions decreases the fusion yield. But this decrease is modulated by the nature of the ion; Li+, a potent "water structure maker," is less effective than Na+ or K+. Ca2+, when present in the millimolar range, leads to the lysis of the cells. Mg2+, when present at concentrations smaller than 4 mM, promotes the fusion but prevents it at larger concentrations. Microelectrophoresis measurements show that the electric surface charge is not strongly affected by these changes in ionic content. Our observations are relevant of a modulation of the cell-cell interactions by the ionic content of the bathing medium.