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Oscillatory hyperpolarizations and resting membrane potentials of mouse fibroblast and macrophage cell lines.
Author(s) -
Ince C,
Leijh P C,
Meijer J,
Van Bavel E,
Ypey D L
Publication year - 1984
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.1984.sp015313
Subject(s) - hyperpolarization (physics) , membrane potential , biophysics , chemistry , electrode , membrane , conductance , electrophysiology , cell membrane , biology , biochemistry , neuroscience , physics , stereochemistry , condensed matter physics , nuclear magnetic resonance spectroscopy
L cells (a mouse fibroblast cell line) and macrophages have been reported to exhibit slow oscillatory hyperpolarizations and relatively low membrane potentials, when measured with glass micro‐electrodes. This paper describes the role of micro‐electrode‐induced leakage in these oscillations for L cells and a mouse macrophage cell line (P388D1). Both L cells and macrophages showed fast negative‐going peak‐shaped potential transients upon micro‐electrode entry. This shows that the micro‐electrode introduces a leakage conductance across the membrane. The peak values of these fast transients were less negative for L cells (‐17 mV) than for macrophages (‐39 mV), although their sustained resting membrane potentials were about equal (‐13 mV). This indicates that the pre‐impaled membrane potential of macrophages is more negative than that of L cells. Ionophoretic injection of Ca2+ into the P388D1 macrophages showed the existence of a Ca2+ ‐dependent hyperpolarizing conductance presumed to be involved in the oscillatory hyperpolarizations of L cells and macrophages. Cells increased in size by X‐ray irradiation to reduce membrane input resistances were still found to be susceptible to micro‐electrode‐induced leakage. Impalement transients upon entry of a second electrode during a hyperpolarization evoked by a first electrode, were often step‐shaped instead of peak‐shaped due to the high membrane conductance associated with hyperpolarization. Since peak‐shaped impalement transients were always seen with the first impalement both in oscillating and non‐oscillating cells, oscillatory hyperpolarizations cannot be regarded as spontaneously occurring in the unperturbed cells but are induced by micro‐electrode penetration. Since the hyperpolarizing response can be evoked by ionophoretic injection of Ca2+, and oscillatory as well as single hyperpolarizing responses are absent in a Ca2+ ‐free medium, it is concluded that the Ca2+ needed intracellularly to activate the hyperpolarizing responses enters the cell via the leakage pathway introduced by the measuring electrode.