{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T19:48:57Z","timestamp":1792180137667,"version":"4.4.0"},"reference-count":0,"publisher":"Rockefeller University Press","issue":"4","content-domain":{"domain":["rupress.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1993,10,1]]},"abstract":"<jats:p>Ca(2+)-activated K+[K(Ca)] channels in resting and activated human peripheral blood T lymphocytes were characterized using simultaneous patch-clamp recording and fura-2 monitoring of cytosolic Ca2+ concentration, [Ca2+]i. Whole-cell experiments, using EGTA-buffered pipette solutions to raise [Ca2+]i to 1 microM, revealed a 25-fold increase in the number of conducting K(Ca) channels per cell, from an average of 20 in resting T cells to &amp;gt; 500 channels per cell in T cell blasts after mitogenic activation. The opening of K(Ca) channels in both whole-cell and inside-out patch experiments was highly sensitive to [Ca2+]i (Hill coefficient of 4, with a midpoint of approximately 300 nM). At optimal [Ca2+]i, the open probability of a K(Ca) channel was 0.3-0.5. K(Ca) channels showed little or no voltage dependence from -100 to 0 mV. Single-channel I-V curves were linear with a unitary conductance of 11 pS in normal Ringer and exhibited modest inward rectification with a unitary conductance of approximately 35 pS in symmetrical 160 mM K+. Permeability ratios, relative to K+, determined from reversal potential measurements were: K+ (1.0) &amp;gt; Rb+ (0.96) &amp;gt; NH4+ (0.17) &amp;gt; Cs+ (0.07). Slope conductance ratios were: NH4+ (1.2) &amp;gt; K+ (1.0) &amp;gt; Rb+ (0.6) &amp;gt; Cs+ (0.10). Extracellular Cs+ or Ba2+ each induced voltage-dependent block of K(Ca) channels, with block increasing at hyperpolarizing potentials in a manner suggesting a site of block 75% across the membrane field from the outside. K(Ca) channels were blocked by tetraethylammonium (TEA) applied externally (Kd = 40 mM), but were unaffected by 10 mM TEA applied inside by pipette perfusion. K(Ca) channels were blocked by charybdotoxin (CTX) with a half-blocking dose of 3-4 nM, but were resistant to block by noxiustoxin (NTX) at 1-100 nM. Unlike K(Ca) channels in Jurkat T cells, the K(Ca) channels of normal resting or activated T cells were not blocked by apamin. We conclude that while K(Ca) and voltage-gated K+ channels in the same cells share similarities in ion permeation, Cs+ and Ba2+ block, and sensitivity to CTX, the underlying proteins differ in structural characteristics that determine channel gating and block by NTX and TEA.<\/jats:p>","DOI":"10.1085\/jgp.102.4.601","type":"journal-article","created":{"date-parts":[[2004,5,13]],"date-time":"2004-05-13T23:51:34Z","timestamp":1084492294000},"page":"601-630","update-policy":"https:\/\/doi.org\/10.1085\/jgp.crossmarkpolicy","source":"Crossref","is-referenced-by-count":175,"title":["Calcium-activated potassium channels in resting and activated human T lymphocytes. Expression levels, calcium dependence, ion selectivity, and pharmacology."],"prefix":"10.1085","volume":"102","author":[{"given":"S","family":"Grissmer","sequence":"first","affiliation":[{"name":"Department of Physiology and Biophysics, University of California, Irvine 92717."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"A N","family":"Nguyen","sequence":"additional","affiliation":[{"name":"Department of Physiology and Biophysics, University of California, Irvine 92717."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M D","family":"Cahalan","sequence":"additional","affiliation":[{"name":"Department of Physiology and Biophysics, University of California, Irvine 92717."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"291","published-online":{"date-parts":[[1993,10,1]]},"container-title":["The Journal of general physiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/rupress.org\/jgp\/article-pdf\/102\/4\/601\/1767681\/601.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/rupress.org\/jgp\/article-pdf\/102\/4\/601\/1767681\/601.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,7,26]],"date-time":"2023-07-26T10:29:51Z","timestamp":1690367391000},"score":1,"resource":{"primary":{"URL":"https:\/\/rupress.org\/jgp\/article\/102\/4\/601\/26300\/Calcium-activated-potassium-channels-in-resting"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1993,10,1]]},"references-count":0,"journal-issue":{"issue":"4","published-print":{"date-parts":[[1993,10,1]]}},"URL":"https:\/\/doi.org\/10.1085\/jgp.102.4.601","relation":{},"ISSN":["0022-1295","1540-7748"],"issn-type":[{"value":"0022-1295","type":"print"},{"value":"1540-7748","type":"electronic"}],"subject":[],"published":{"date-parts":[[1993,10,1]]}}}