Ion channels in human THP-1 monocytes

J Membr Biol. 1996 Jul;152(2):117-30. doi: 10.1007/s002329900091.


The THP-1 human monocytic leukemia cell line is a useful model of macrophage differentiation. Patch clamp methods were used to identify five types of ion channels in undifferentiated THP-1 monocytes. (i) Delayed rectifier K+ current, IDR, was activated by depolarization to potentials positive to -50 mV, inactivated with a time constant of several hundred msec, and recovered from inactivation with a time constant approximately21 sec. IDR was inhibited by 4-aminopyridine (4-AP), tetraethylammonium (TEA+), and potently by charybdotoxin (ChTX). (ii) Ca-activated K+ current (ISK) dominated whole-cell currents in cells studied with 3-10 micron [Ca2+]i. ISK was at most weakly voltage-dependent, with reduced conductance at large positive potentials, and was inhibited by ChTX and weakly by TEA+, Cs+, and Ba2+, but not 4-AP or apamin. Block by Cs+ and Ba2+ was enhanced by hyperpolarization. (iii) Nonselective cation current, Icat, appeared at voltages above +20 mV. Little time-dependence was observed, and a panel of channel blockers was without effect. (iv) Chloride current, ICl, was present early in experiments, but disappeared with time. (v) Voltage-activated H+ selective current is described in detail in a companion paper (DeCoursey & Cherny, 1996. J. Membrane Biol. 152:2). The ion channels in THP-1 cells are compared with channels described in other macrophage-related cells. Profound changes in ion channel expression that occur during differentiation of THP-1 cells are described in a companion paper (DeCoursey et al., 1996. J. Membrane Biol. 152:2).

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 4-Aminopyridine / pharmacology
  • Apamin / pharmacology
  • Calcium / pharmacology
  • Cations, Divalent / pharmacology
  • Charybdotoxin / pharmacology
  • Chloride Channels / drug effects
  • Chloride Channels / metabolism
  • Humans
  • Ion Channel Gating / drug effects
  • Ion Channels / drug effects
  • Ion Channels / metabolism*
  • Leukemia, Monocytic, Acute / metabolism
  • Leukemia, Monocytic, Acute / pathology*
  • Monocytes / drug effects
  • Monocytes / physiology*
  • Neoplasm Proteins / metabolism*
  • Potassium / metabolism
  • Potassium Channels / drug effects
  • Potassium Channels / metabolism
  • Potassium Channels, Voltage-Gated*
  • Tetraethylammonium
  • Tetraethylammonium Compounds / pharmacology
  • Tumor Cells, Cultured


  • Cations, Divalent
  • Chloride Channels
  • Ion Channels
  • Neoplasm Proteins
  • Potassium Channels
  • Potassium Channels, Voltage-Gated
  • Tetraethylammonium Compounds
  • charybdotoxin receptor
  • potassium channel protein I(sk)
  • Charybdotoxin
  • Apamin
  • Tetraethylammonium
  • 4-Aminopyridine
  • Potassium
  • Calcium