Calcium dynamics in cultured heart cells exposed to defibrillator-type electric shocks.
Spatial and temporal changes in intracellular calcium ion concentration and transmembrane voltage were recorded optically from single-isolated cultured chick-embryo heart cells exposed to high-voltage, defibrillator-type shocks. Fluorescence changes were measured during 5 msec electric shocks of field strengths up to 56 volts/cm in single myocytes stained with a Ca(++)-sensitive or voltage-sensitive dye. Shocks caused a reversible period of depolarization, elevated cytosolic Ca++, and refractoriness. Intracellular Ca++ elevation had two temporal phases: first, a Ca++ spike with morphology independent of shock intensity; and second, a prolonged Ca++ elevation with a shock-intensity-dependent magnitude and duration, and with greatest Ca++ elevation at the poles of the cell adjacent to the electrodes. The prolonged elevation (second phase) was initiated earlier at the anode-facing pole of the cell than at the cathode-facing pole. These results suggest that postshock Ca++ entry consists of two parts: early normal entry through excitation channels plus a prolonged elevation which may be related to cellular damage.
Krauthamer
V
V
Office of Science and Technology, Center for Devices and Radiological Health, Food and Drug Administration, Rockville, Maryland 20857, U.S.A. vik@fdadr.cdrh.fda.gov
Jones
J L
JL
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D004558:Electric Stimulation; D008564:Membrane Potentials; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*
D002118:Calcium