title: Transmembrane calcium influx induced by ac electric fields.
abstract: Exogenous electric fields induce cellular responses including redistribution of integral membrane proteins, reorganization of microfilament structures, and changes in intracellular calcium ion concentration ([Ca2+]i). Although increases in [Ca2+]i caused by application of direct current electric fields have been documented, quantitative measurements of the effects of alternating current (ac) electric fields on [Ca2+]i are lacking and the Ca2+ pathways that mediate such effects remain to be identified. Using epifluorescence microscopy, we have examined in a model cell type the [Ca2+]i response to ac electric fields. Application of a 1 or 10 Hz electric field to human hepatoma (Hep3B) cells induces a fourfold increase in [Ca2+]i (from 50 nM to 200 nM) within 30 min of continuous field exposure. Depletion of Ca2+ in the extracellular medium prevents the electric field-induced increase in [Ca2+]i, suggesting that Ca2+ influx across the plasma membrane is responsible for the [Ca2+]i increase. Incubation of cells with the phospholipase C inhibitor U73122 does not inhibit ac electric field-induced increases in [Ca2+]i, suggesting that receptor-regulated release of intracellular Ca2+ is not important for this effect. Treatment of cells with either the stretch-activated cation channel inhibitor GdCl3 or the nonspecific calcium channel blocker CoCl2 partially inhibits the [Ca2+]i increase induced by ac electric fields, and concomitant treatment with both GdCl3 and CoCl2 completely inhibits the field-induced [Ca2+]i increase. Since neither Gd3+ nor Co2+ is efficiently transported across the plasma membrane, these data suggest that the increase in [Ca2+]i induced by ac electric fields depends entirely on Ca2+ influx from the extracellular medium.
authors: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School Boston, Massachusetts 02115, USA.
authors: M R
authors: MR
authors: Cho
authors: H S
authors: HS
authors: Thatte
authors: M T
authors: MT
authors: Silvia
authors: D E
authors: DE
authors: Golan
mesh_terms: D001692:Biological Transport; D001696:Biomechanical Phenomena; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism*; D004574:Electromagnetic Fields; D006801:Humans; D015640:Ion Channel Gating; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D014407:Tumor Cells, Cultured
chemical_list: D015220:Calcium Channels