Spontaneous and induced membrane hyperpolarizations in macrophages

Abstract

The electrophysiological properties of guinea pig peritoneal macrophages cultured in vitro were studied using standard intracellular recording techniques. The mean transmembrane potential, input resistance and time constant recorded from these cells were -13.1 mV, 143 Mohms, and 18 msec respectively. The majority of macrophages exhibited spontaneous hyperpolarizations (HA) of 4-8 seconds in duration and 10-50 mV in amplitude. Mouse peritoneal macrophages and human monocyte-derived macrophages manifested similar HA. HA could be induced by either mechanical stimulation or application of hyperpolarizing currents of 2-8 namps. HA had a mean reversal potential of -53 mV. Increasing the extracellular [K+] 10-fold resulted in a 50 mV shift in reversal potential. Addition of EGTA (1.5 mM) inhibited both spontaneous and evoked macrophage HA in the presence of excess Mg++. The divalent cation ionophore, A23187 induced prolongation of HA at low concentration (0.6 X 10(-6) M) and resulted in sustained hyperpolarization at higher concentration (2.0 X 10(-6) M). Addition to EGTA to cells treated with A23187 abolished HA. These data indicate that: (1) cultured macrophages from a variety of species exhibit spontaneous and induced HA, (2) development of HA is related to an increase in membrane permeability to K+, and (3) Ca++ may regulate the spontaneous and evoked electrical activity of the macrophage membrane presumably by affecting K+ permeability.

Interaction of chemotactic factors with human macrophages: induction of transmembrane potential changes

“…Occasionally, a membrane hyperpolarization lasting several seconds was seen upon puncturing a cell, but otherwise, spontaneous hyperpolariza- tions were infrequent. In this respect these cells, cultured from peripheral blood monocytes, differed from guinea pig peritoneal exudate macrophages which exhibit more frequent spontaneous hyperpolarization (9). Hyperpolarizations could be induced, however, by either mechanical or electrical (large depolarizing pulses) stimulation as we previously reported in macrophages of guinea pig, human, and mouse (9).…”

“…Macrophages of guinea pig, mouse, and humans have previously been shown to exhibit spontaneous membrane hyperpolarizations which are associated with increased membrane permeability to potassium (9). Although the functional significance of these hyperpolarizations was not established, the action of both the calcium ionophore A23187 (which produced prolonged hyperpolarizations) and magnesium-ethylene glycol bis[fl-aminoethyl ether]N,N'-tetraacetic acid (Mg-EGTA; which blocked both the spontaneous and ionophore-induced hyperpolarizations) indicated a role for calcium in these events.…”

Mechanically induced electrical responses in murine mammary epithelial cells in primary culture

“…Several investigators have proposed that the physiological role of the hyperpolarizing response in fibroblast L cells and macrophages may be related to contractile systems, such as phagocytosis and pinocytosis [3,9,10]. The physiological significance of the mechanically responsive electri~ah ac~v~y ~n mammary ~e~s ~s uneven) m ~ne period oi cel~t growth and milk secretion.…”

“…Electrically non-excitable cells, such as fibroblast L cells [1,2], macrophages [3], erythrocytes [4], and fertilized hamster eggs [5], exhibit rhythmic hyperpolarizing potentials. Mouse mammary epithelial cells in culture, which are also not electrically excitable, show a spontaneous hyperpolarizing response when cultured in the presence of epidermal growth factor (EGF), and produce a depolarizing response when incubated with insulin [6].…”

“…Earlier studies have shown that a hyperpolarization can be induced mechanically in electrically non-excitable cells [1][2][3]. To gain further insight into the mechanisms underlying the electrical activity of mammary cells, we examined the effects of mechanical stimulation on cultured mammary epithelial cells.…”