Electrophysiology of phagocytic membranes. I. Potassium-dependent slow membrane hyperpolarizations in mice...

Electrophysiological properties of activated mouse macrophages cultured in vitro were studied using microelectrode techniques. In a high percentage of the individual cells analysed a slow hyperpolarization (SH) was observed with a concomitant decrease (2--4 times) of the input resistance. Increasing doses of tetraethyl ammonium progressively reduce the amplitude of the SH and at a concentration of 15 mM complete blockade of the phenomena is observed. Valinomycin, at a concentration of 10(-7) M produces rapid and permanent hyperpolarization, with a shift in the membrane potential to about --50 mV. These data strongly support the previously proposed hypothesis that the development of SH is due to an increase in the membrane permeability to potassium ions.