Ca2+- and voltage-dependent K+ conductance in dispersed parathyroid cells.
The membrane ionic conductances of dispersed parathyroid cells kept in primary culture were studied using the "whole-cell" and "inside-out excised patch" variants of the patch-clamp technique. The major component of the total current was a voltage-dependent outward K+ current without an appreciable inward current. The amplitude of the K+ current was markedly reduced when free internal Ca2+ was buffered by addition of 10 mM EGTA. Recordings of single-channel current in excised membrane patches revealed the presence of K+ channels with large unitary conductance (200 pS in symmetrical 130 mM K+ solutions) which were also activated by depolarization when internal Ca2+ concentration was about 10(-5)-10(-6) M. At any membrane voltage these channels were closed most of the time at internal Ca2+ concentrations lower than 10(-10) M. These results demonstrate the existence of a Ca2+- and voltage-dependent K+ permeability in parathyroid cells which may participate in the unusual membrane potential changes induced by alterations of external Ca2+ and, possibly, in the regulation of parathormone secretion.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002463:Cell Membrane Permeability; D004553:Electric Conductivity; D005260:Female; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D010280:Parathyroid Glands / Q000502:physiology*; D011188:Potassium / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
D007473:Ion Channels; D011188:Potassium; D002118:Calcium