AJP - Cell Physiology, Vol 256, Issue 6 C1277-C1282, Copyright © 1989 by American Physiological Society
Inwardly rectifying K+ current in osteoclasts
S. M. Sims and S. J. Dixon
Department of Physiology, University of Western Ontario, London, Canada.
Membrane properties of freshly isolated rat osteoclasts were studied using
the whole cell patch-clamp recording technique. The membrane potential
could switch between two stable levels, approximately -70 and -15 mV.
Voltage-clamp studies indicated that osteoclasts exhibited marked inward
rectification, with hyperpolarizing voltage commands from -70 mV activating
large inward currents. No voltage-dependent currents were observed in
response to depolarization. An increase in external K+ concentration
shifted the current-voltage relationship positive in a manner predicted for
K+ current. Furthermore, barium and cesium reversibly suppressed the inward
current. Thus the dominant current evident in osteoclasts was inwardly
rectifying K+ current, resembling that found in a number of cell types,
including cardiac and skeletal muscle and oocytes. The current-voltage
relationship of osteoclasts was "N-shaped" and could intersect the
zero-current level at three potentials, accounting for two stable membrane
potentials. Switching of membrane potential between these two levels may
regulate a number of the cellular processes involved in bone resorption.
