Linked Life Data

8799891

Source:http://linkedlifedata.com/resource/pubmed/id/8799891

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:dateCreated
1996-12-5
pubmed:abstractText
1. Large-conductance calcium-activated K+ channels (BK channels) often display long closed intervals at higher levels of Ca2+. To gain further insight into possible mechanisms for these intervals, currents were recorded from single BK channels, using the patch clamp technique, from patches of membrane excised from primary cultures of rat skeletal muscle. 2. High intracellular calcium concentrations ([Ca2+]i; 10-1000 microM) induced a low activity mode and revealed isolated long shut intervals. Neither of these phenomena were due to the Ba2+ that typically contaminates reagent grade salts. 3. The low activity mode was characterized by typically single brief open intervals with mean durations of 0.1 ms, separated by long shut intervals with mean durations of 100 ms. The very low open probability of about 0.001 during the low activity mode would make a sojourn to this mode functionally equivalent to a sojourn to an inactive state. The durations of sojourns in the low activity mode were exponentially distributed, with the mean durations ranging from about 1 s in 10 microM Ca(i)2+, to 4.5 s in 1000 microM Ca(i)2+. With increased filtering, the brief open intervals would escape detection so that a sojourn to the low activity mode would appear as a single shut interval. A typical channel spent less than 5% of its time in the low activity mode for [Ca2+]i < 10 microM. This increased to about 30% for [Ca2+]i > 100-1000 microM. A kinetic model with three closed states and two open states could approximate the gating of the low activity mode. 4. The isolated long shut intervals were not from the low activity mode, suggesting a different underlying mechanism. Their frequency of occurrence of about 0.3 s-1 did not increase with increasing [Ca2+]i, indicating that they did not arise from a slow Ca2+ block. Their durations were exponentially distributed, with a mean of 127 ms, which was independent of [Ca2+]i, suggesting that a single Ca(2+)-independent closed state or block underlies the isolated long shut intervals. At higher [Ca2+]i, up to 60% of the shut time could be spent in the isolated long shut intervals. 5. These observations suggest that activation of BK channels by high [Ca2+]i can be limited by sojourns to a low activity mode and also by isolated long shut intervals, two additional phenomena that will have to be accounted for in the gating of BK channels.
pubmed:grant
pubmed:commentsCorrections
http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-1529355, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-1701554, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-2122519, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-2421796, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-2423151, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-2432248, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-2435330, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-3235973, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-450063, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-6207437, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-6273730, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-6293598, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-6296366, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-6315858, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-6317854, http://linkedlifedata.com/resource/pubmed/commentcorrection/8799891-7919030
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0022-3751
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
493 ( Pt 3)
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
673-89
pubmed:dateRevised
2009-11-18
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
High Ca2+ concentrations induce a low activity mode and reveal Ca2(+)-independent long shut intervals in BK channels from rat muscle.
pubmed:affiliation
Department of Physiology and Biophysics, University of Miami School of Medicine, FL 33101, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't