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Differential expression of inward and outward potassium currents in the macrophage‐like cell line J774.1.
Author(s) -
Gallin E K,
Sheehy P A
Publication year - 1985
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1985.sp015911
Subject(s) - reversal potential , chemistry , membrane potential , hyperpolarization (physics) , inward rectifier potassium ion channel , conductance , biophysics , potassium , patch clamp , electrophysiology , potassium channel , voltage clamp , analytical chemistry (journal) , medicine , ion channel , biochemistry , stereochemistry , biology , physics , chromatography , condensed matter physics , receptor , organic chemistry , nuclear magnetic resonance spectroscopy
J774.1 cells, a mouse‐derived macrophage‐like tumour cell line, were voltage clamped using whole‐cell patch‐clamp techniques. Cells were maintained in suspension cultures and plated at varying times before recording. The average zero‐current potential of long‐term adherent (greater than 24 h) cells was ‐77.6 mV. A tenfold increase in [K]o produced a 49 mV shift in zero‐current potential. Freshly plated cells (less than 24 h) expressed two voltage‐dependent currents: an outward current expressed transiently from 1 to 12 h post‐plating and an inward current expressed 2‐4 h post‐plating which persisted in 100% of long‐term adherent cells. Inward current was dependent upon voltage, time and [K]o 1/2, similar to the anomalous rectifier of other tissues. The conductance activated at potentials negative to ‐50 mV and plateaued at potentials negative to ‐110 mV. Inactivation was evident at potentials negative to ‐100 mV. Both the rate and extent of inactivation increased with hyperpolarization. Inward rectification was blocked by external BaCl2 or CsCl. The outward current was time‐ and voltage‐dependent. The instantaneous I/V curves derived from tail experiments reversed at the potassium equilibrium potential (EK). A tenfold change of [K]o shifted the reversal potential 52 mV, indicating that the current was carried by potassium. This conductance activated at potentials positive to ‐50 mV, plateaued at potentials positive to ‐10 mV and inactivated completely with an exponential time course at all potentials. At voltages positive to ‐25 mV the rate of inactivation was independent of voltage. The outward current was blocked by 4‐aminopyridine or D600. During the first 10 min after attaining a whole‐cell recording, the conductance/voltage relation of the outward current shifted to more negative voltages and peak conductance showed a slight increase; recordings then stabilized. The voltage dependence of the inward current did not shift with time but wash‐out of inward current was observed in some cells. The J774.1 cell line can serve as a model for the study of the role of voltage‐dependent ionic conductances in macrophages.