A flickery block of a K+ channel mediated by extracellular Ca2+ and other agonists of the Ca2+-sensing receptors in dispersed bovine parathyroid cells.
Single K+ channel activities in parathyroid cells were studied using the patch-clamp technique. A K+ channel modulated by external Ca2+ (Ca2+o) was identified. This channel had a unitary conductance of 109pS at 150 mM K+o in the pipette solution. An increase in Ca2+o from 0.5-0.75 to 2-3 mM induced a flickery partial block of the channel over a wide voltage range. The mechanism of channel blockade included a significant increase in the number of closings per burst and a reduction of the mean open times. Addition of other divalent and polyvalent agonists of the Ca2+-sensing receptor (CaR) induced a similar channel blockade. With its typical characteristics and flickery block by CaR agonists, this channel differs from previously described types of K+ channels. It is probably strongly coupled to the CaR and may contribute to the depolarization of parathyroid cells which is known to occur at elevated levels of Ca2+o.
Vassilev
P M
PM
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Kanazirska
M P
MP
Ye
C
C
Francis
J
J
Hong
K
K
Brown
E M
EM
D000818:Animals; D002118:Calcium / Q000819:agonists / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000187:drug effects*; D002412:Cations / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000378:metabolism*; D007700:Kinetics; D010280:Parathyroid Glands / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D002412:Cations; D002413:Cations, Divalent; D015221:Potassium Channels; D002118:Calcium