Control of intracellular calcium by membrane potential in human melanoma cells.
The modulation of intracellular calcium ([Ca2+]i) by the membrane potential was investigated in human melanoma cells by combining the nystatin-perforated patch-clamp technique with Ca2+ measurements. Voltage steps to -100 mV induced a rise in [Ca2+]i and a creeping inward current. These effects were absent in Ca(2+)-free solution and could be blocked by Ni2+ or La3+. Voltage ramps revealed a close correlation between [Ca2+]i and voltage, with the strongest voltage dependence around the resting potential. Long-lasting tail currents, closely correlated with the rise in [Ca2+]i and a reversal potential close to the K+ equilibrium potential, occurred if the membrane potential was clamped back to 0 mV. They were absent if intracellular K+ was replaced by Cs+ and blocked by extracellular tetraethylammonium (5 mM), Ba2+ (1 mM), or a membrane-permeable adenosine 3',5'-cyclic monophosphate analogue. These observations are discussed in relation to cell proliferation. The enhanced expression of K+ channels during cell proliferation provides a positive-feedback mechanism resulting in long-term changes in [Ca2+]i required for the G1-S transition in the cell cycle.
Nilius
B
B
Department of Physiology, Katholieke Universitiet Leuven, Belgium.
Schwarz
G
G
Droogmans
G
G
D001464:Barium / Q000378:metabolism; D017609:Barium Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D004594:Electrophysiology / Q000379:methods; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D006801:Humans; D007700:Kinetics; D008545:Melanoma; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D013050:Spectrometry, Fluorescence; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured
D017609:Barium Compounds; D002712:Chlorides; D005456:Fluorescent Dyes; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D013873:Thionucleotides; C024986:barium chloride; C049925:fura-2-am; D001464:Barium; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D019789:Tetraethylammonium; D000242:Cyclic AMP; D002118:Calcium; D016257:Fura-2