Activation of BK Channels in Rat Chromaffin Cells Requires Summation of Ca2+ Influx From Multiple Ca2+Channels

摘要: Large-conductance Ca(2+) and voltage-dependent K(+) channels (BK channels) in many tissues require high concentrations for activation therefore might be expected to tightly coupled channels. However, most cases, little is known about the relative organization of BK involved their activation. We probed nature rat chromaffin cells by manipulating influx through altering cellular buffering using EGTA bis-(o-aminophenoxy)-N,N,N', N'-tetraacetic acid (BAPTA). The results were analyzed determine distance between that would consistent with experimental data. Most are close enough resistant action millimolar EGTA, but far inhibited BAPTA. Analysis EGTA/BAPTA suggests at a 50 160 nm from A model assumes random distribution fails account observed [Ca(2+)](i) detected channels, suggesting specific mechanism may exist mediate functional coupling these Importantly, effects BAPTA cannot explained assuming one-to-one Rather, number appears act concert regulate behavior any individual channel. Thus differences channel open probabilities extent domain overlap sites