Using the patch-clamp whole-cell recording technique, we investigated the influence of external Ca2+, Ba2+, K+, Rb+, and internal Ca2+ on the rate of K+ channel inactivation in the human T lymphocyte-derived cell line, Jurkat E6-1. Raising external Ca2+ or Ba2+, or reducing external K+, accelerated the rate of the K+ current decay during a depolarizing voltage pulse. External Ba2+ also produced a use-dependent block of the K+ channels by entering the open channel and becoming trapped inside. Raising internal Ca2+ accelerated inactivation at lower concentrations than external Ca2+, but increasing the Ca2+ buffering with BAPTA did not affect inactivation. Raising [K+]o or adding Rb+ slowed inactivation by competing with divalent ions. External Rb+ also produced a use-dependent removal of block of K+ channels loaded with Ba2+ or Ca2+. From the removal of this block we found that under normal conditions approximately 25% of the channels were loaded with Ca2+, whereas under conditions with 10 microM internal Ca2+ the proportion of channels loaded with Ca2+ increased to approximately 50%. Removing all the divalent cations from the external and internal solution resulted in the induction of a non-selective, voltage-independent conductance. We conclude that Ca2+ ions from the outside or the inside can bind to a site at the K+ channel and thereby block the channel or accelerate inactivation.
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1 April 1989
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April 01 1989
Divalent ion trapping inside potassium channels of human T lymphocytes.
S Grissmer,
S Grissmer
Department of Physiology and Biophysics, University of California, Irvine 92717.
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M D Cahalan
M D Cahalan
Department of Physiology and Biophysics, University of California, Irvine 92717.
Search for other works by this author on:
S Grissmer
Department of Physiology and Biophysics, University of California, Irvine 92717.
M D Cahalan
Department of Physiology and Biophysics, University of California, Irvine 92717.
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1989) 93 (4): 609–630.
Citation
S Grissmer, M D Cahalan; Divalent ion trapping inside potassium channels of human T lymphocytes.. J Gen Physiol 1 April 1989; 93 (4): 609–630. doi: https://doi.org/10.1085/jgp.93.4.609
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