The plasma membrane potential of human neutrophils. Role of ion channels and the sodium/potassium pump.
Calcium-depleted human neutrophils are depolarised when suspended in calcium-free media containing sodium ions, and are repolarised by extracellular replenishment of Ca2+. The depolarisation is due to a high inward sodium current, which is blocked by calcium and by several other divalent cations, but not by barium. Addition of calcium results in a rise in the cytosolic concentration from approx. 20 nM to the resting level of approx. 130 nM. Calcium influx is strongly accelerated by a voltage-gated calcium channel. This channel might be responsible for the depolarising Na+ current in the absence of divalent cations. In the polarised state the neutrophil membrane has a high intrinsic permeability to K+, which may be low or absent in the depolarised state. Generation of membrane potential from the depolarised state is mainly due to the electrogenic sodium/potassium pump. However, the resting potential of about -75 mV is maintained primarily by the K+ conductance, and only to a small extent by the sodium/potassium pump.
Majander
A
A
Department of Medical Chemistry, University of Helsinki, Finland.
Wikström
M
M
D002118:Calcium / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D003600:Cytosol / Q000378:metabolism; D004563:Electrochemistry; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009504:Neutrophils / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism
D015220:Calcium Channels; D015221:Potassium Channels; D015222:Sodium Channels; D011188:Potassium; D002118:Calcium