Differential expression of inward and outward potassium currents in the macrophage‐like cell line J774.1.

Abstract

5. 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]0 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 D600.6. 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

Electrical Membrane Properties in the Model Leishmania-Macrophage

“…Thus the resting potential of many animal cells is close to E K+ . Most data suggest a Vm for the macrophage close to E K+ that varies with changes in [K + ] o (Gallin & Sheehy, 1985;Judge et al, 1994 (Gallin & Sheehy, 1985), but suggesting the contribution of other ions. A contribution of the electrogenic activity of a Na + /K + ATPase pump (Gallin & Livengood, 1983) of about 6 mV to the macrophage Vm could explain the deviation found.…”

“…Values of around -75 mV have been recorded (McCann et al, 1987;Gallin & Sheehy, 1985;Buisman et al, 1988), and it has been suggested that time of adherence is not important because rapid hyperpolarization was observed after only 30 minutes post-adhesion (Gallin & Sheehy, 1985). Values of -60 to -70 mV were recorded in J774 and in peritoneal macrophages (Randriamampita & Trautmann, 1987).…”

“…A contribution of the electrogenic activity of a Na + /K + ATPase pump (Gallin & Livengood, 1983) of about 6 mV to the macrophage Vm could explain the deviation found. The depolarization obtained after inhibition of I KIR by Ba 2+ has implicated this current in the macrophage Vm value (Randriamampita & Trautmann, 1987), particularly after long periods of adherence (Gallin & Sheehy, 1985). More recently it has been proposed that Kv1.3 voltage gated channels establish macrophage Vm (Mackenzie et al, 2003) as shown in T lymphocytes (Panyi et al, 2004).…”

“…The passive electrical membrane properties of J774.A1, a mouse macrophage-like cell line, vary with time after adherence onto glass, where increased membrane capacitance (Cm) and hyperpolarization have been observed (Gallin & Sheehy, 1985;McKinney & Gallin, 1990;Camacho, unpublished data). Active electrical properties also vary, with large outward currents (I OUT ) recorded during the first 8 hours post-adherence with minimal inward rectifying current (I KIR ) (Gallin & Sheehy, 1985;Randriamampita & Trautmann, 1987). I OUT and I KIR have similar amplitudes after 24 hours post-adherence (Gallin & Sheehy, 1985), but after 48 hours the situation reverses, with predominant I KIR and negligible I OUT (McKinney & Gallin, 1990).…”

“…Active electrical properties also vary, with large outward currents (I OUT ) recorded during the first 8 hours post-adherence with minimal inward rectifying current (I KIR ) (Gallin & Sheehy, 1985;Randriamampita & Trautmann, 1987). I OUT and I KIR have similar amplitudes after 24 hours post-adherence (Gallin & Sheehy, 1985), but after 48 hours the situation reverses, with predominant I KIR and negligible I OUT (McKinney & Gallin, 1990). We have therefore controlled for time of adherence onto glass in some of our experiments to guarantee similar amplitudes for I OUT and I KIR (Forero et al, 1999;Camacho et al, 2008;Quintana et al, 2010).…”