A Ca(2+)-dependent K(+)-channel in freshly isolated and cultured chick osteoclasts.
Calcium-activated potassium channels were found in embryonic chick osteoclasts using the patch-clamp technique. The activity of the channel was increased by both membrane depolarisation and an increase in intracellular Ca2+ concentration in the range 10(-5) to 10(-3) M. In the cell-attached-patch configuration the channel was only active at extreme depolarising potentials. Ca2+ addition to the cytoplasm via ionomycin increased channel activity at the resting membrane potential of the osteoclast. The channel had a single-channel conductance of 150 pS in the inside-out patch under symmetrical K+ conditions (150 mM) and was selective for potassium ions. During sustained application of increased [Ca2+] at the cytoplasmic side of inside-out patches, channel activity sometimes decreased again after the initial increases (desensitization). The results established the properties of the single channels underlying an outward rectifying K+ conductance in chick osteoclasts described previously by us.
Weidema
A F
AF
Department of Physiology and Physiological Physics, Leiden University, The Netherlands.
Ravesloot
J H
JH
Panyi
G
G
Nijweide
P J
PJ
Ypey
D L
DL
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D002642:Chick Embryo; D008564:Membrane Potentials; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects*; D012964:Sodium / Q000378:metabolism
D015221:Potassium Channels; D012964:Sodium; D002118:Calcium