COMPARISON OF SUBSARCOLEMMAL AND BULK CALCIUM-CONCENTRATION DURING SPONTANEOUS CALCIUM-RELEASE IN RAT VENTRICULAR MYOCYTES
COMPARISON OF SUBSARCOLEMMAL AND BULK CALCIUM-CONCENTRATION DURING SPONTANEOUS CALCIUM-RELEASE IN RAT VENTRICULAR MYOCYTES
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DOI：
10.1113/jphysiol.1995.sp020991
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发表时间：
1995-11-01
影响因子：
5.5
通讯作者：
EISNER, DA
中科院分区：
文献类型：
--
作者：
TRAFFORD, AW;DIAZ, ME;EISNER, DA
1. The aim of these experiments was to compare the time course of changes in intracellular Ca2+ concentration ([Ca2+](i)) measured in the bulk cytoplasm with those estimated to occur near the sarcolemma. Sarcolemmal Na+-Ca2+ exchange current and [Ca2+](i) were measured in single, voltage-clamped ventricular myocytes.2. Spontaneous Ca2+ release from the sarcoplasmic reticulum (SR) resulted in a transient inward current. This current developed and decayed more quickly than the accompanying changes in [Ca2+](i) (measured with indo-1) resulting in a hysteresis between [Ca2+](i) and current. A similar hysteresis was also observed if [Ca2+](i) was elevated with caffeine and was removed if the current was low pass filtered with a time constant of 132 ms.3. Digital video imaging (using flue-3 or calcium green-1 to measure [Ca2+](i)) allowed measurement of [Ca2+](i) at all points in the cell during the wave of spontaneous Ca2+ release. The hysteresis between [Ca2+](i) and current remained, even after allowing for the spatial and temporal properties of this wave.4. The hysteresis can be accounted for if there is a barrier to diffusion of Ca2+ ions separating the bulk cytoplasm from the space under the sarcolemma (into which Ca2+ is released from the sarcoplasmic reticulum). The calculated subsarcolemmal [Ca2+] rises and falls more quickly (and reaches a higher peak) than does the bulk [Ca2+]. The delay introduced by this barrier is equivalent to a time constant of 133 ms.5. The subsarcolemmal space described in this paper may be equivalent to the 'fuzzy space' previously suggested to be important in controlling SR Ca2+ release.
