Voltage-activated K+ conductances in freshly isolated embryonic chicken osteoclasts.
Patch-clamp measurements on freshly isolated embryonic chicken osteoclasts revealed three distinct types of voltage-dependent K+ conductance. The first type of conductance, present in 72% of the cells, activated at membrane potentials less negative than -30 to -20 mV and reached full activation at +40 mV. It activated with a delay, reached a peak value, and then inactivated with a time constant of approximately 1.5 s. Inactivation was complete or almost so. Recovery from inactivation, at -70 mV, had a time constant of roughly 1 s. The conductance could be blocked, at least partly, by 4 mM 4-aminopyridine. The second type of conductance (present in all cells) activated at membrane potentials more negative than -40 to -80 mV and reached full activation at -130 mV. Activation potential and maximal conductance were dependent on the extracellular K+ concentration. Inactivation of the conductance first became apparent at membrane potentials more negative than -100 mV and was a two-exponential process. The conductance could be blocked by external 5 mM Cs+ ions. The third type of conductance (present in all cells) activated at membrane potentials more positive than +30 mV. Generally, the conductance did not inactivate.
Ravesloot
J H
JH
Department of Cell Biology and Histology, Leiden University, The Netherlands.
Ypey
D L
DL
Vrijheid-Lammers
T
T
Nijweide
P J
PJ
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002586:Cesium / Q000494:pharmacology; D002642:Chick Embryo; D004553:Electric Conductivity; D008564:Membrane Potentials; D010010:Osteoclasts / Q000166:cytology / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*
D000631:Aminopyridines; D015221:Potassium Channels; D002586:Cesium; D015761:4-Aminopyridine