Electrical and ionic controls of tissue cell locomotion in DC electric fields.

The motility of fish epidermal cells (keratocytes) was examined in the presence and absence of DC electric fields. In fields of 0.5-15 V/cm, single epidermal cells, cell clusters, and cell sheets migrate toward the cathode. Cell clusters and sheets break apart into single migratory cells in the upper range of these field strengths. During locomotion, keratocytes extend broad lamellipodia, which contain a pervasive actomyosin network. The lamellipodial extension and locomotion of keratocytes are reversibly inhibited by a variety of calcium channel antagonists, whereas their motility is unaffected by hyperpolarizing and depolarizing (low and high K+) media. Microtubule disassembly has no effect on cell morphology, motility or the ability of the cells to be guided by a DC electric field. Using these results, the role that membrane-regulated Ca2+ influx may play in generating cytoskeletal and protrusive activity in keratocytes and other cells is discussed in some detail. Mechanisms by which an external electric field may bias transmembrane ion fluxes and thereby control cell locomotion are also examined.