Voltage-dependent and Ca2(+)-activated ion channels in human neutrophils.
To investigate the regulation of membrane voltage and transmembrane ion fluxes in human neutrophils, we studied plasma membrane currents using the whole-cell patch-clamp method. We observed three distinct ion channel currents: (a) a voltage-dependent K+ current, (b) a Ca2(+)-activated K+ current, and (c) a Ca2(+)-activated Cl- current. The voltage-dependent K+ current was found in cells at rest. Its conductive properties suggested an inwardly rectifying channel. The channel was activated at membrane potentials more positive than -60 mV, suggesting that it may determine the resting membrane potential of neutrophils. Activation of neutrophils by the Ca2+ ionophore ionomycin led to an increase in whole-cell K+ and Cl- currents. The Ca2(+)-activated K+ channel differed from the voltage-dependent K+ channel because it was insensitive to voltage, because it rectified outwardly, and because the voltage-sensitive K+ channel was Ca2(+)-independent. The Ca2(+)-activated Cl- channel showed outward rectification and no apparent voltage dependency. The Ca2(+)-activated K+ and Cl- channels may play a role in cell volume homeostasis and/or cellular activation.
Krause
K H
KH
Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
Welsh
M J
MJ
D002118:Calcium / Q000494:pharmacology*; D018118:Chloride Channels; D002712:Chlorides / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000502:physiology*; D009504:Neutrophils / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*
D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D015221:Potassium Channels; D002118:Calcium