Potentiation of fractional sarcoplasmic reticulum calcium release by total and free intra-sarcoplasmic reticulum calcium concentration
Potentiation of fractional sarcoplasmic reticulum calcium release by total and free intra-sarcoplasmic reticulum calcium concentration
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DOI：
10.1016/s0006-3495(00)76596-9
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发表时间：
2000-01-01
影响因子：
3.4
通讯作者：
Bers, DM
中科院分区：
文献类型：
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作者：
Shannon, TR;Ginsburg, KS;Bers, DM
我们的目的是测量肌浆网（SR）钙含量（[Ca](SRT)）和游离SR [Ca]（[Ca](SR)）对分离兔心室肌细胞在电压箝位过程中释放的SR钙的比例的影响。[Ca](SRT)，通过咖啡因应用测量，通过调节脉冲逐渐增加。在细胞内和细胞外溶液中均缺乏钠，以阻止钠/钙交换。通过i -Ca、[Ca]（SRT）、[Ca](i)和细胞缓冲特性推断瞬时胞质总钙通量。通过钙电流（I-Ca）、SR钙泵和SR被动泄漏的通量进行了评估，以确定SR钙释放通量（J(rel)），激发-收缩（EC）耦合在增益(积分J(rel)/积分/(Ca)和分数SR钙释放方面进行了表征。对于一个小但可测量的[Ca](SRT)，这两个参数几乎为零。增益和分数SR钙释放随[Ca]（SRT）和[Ca]（SR）均呈非线性急剧增加。我们认为EC耦合的增强可以与[Ca]（SRT）和[Ca]（SR）相关。虽然分数SR钙释放与[Ca]（SR）没有线性关系，但SR内钙可能在调节SR钙释放过程中起关键作用。
Our aim was to measure the influence of sarcoplasmic reticulum (SR) calcium content ([Ca](SRT)) and free SR [Ca] ([Ca](SR)) on the fraction of SR calcium released during voltage clamp steps in isolated rabbit ventricular myocytes. [Ca](SRT), as measured by caffeine application, was progressively increased by conditioning pulses. Sodium was absent in both the intracellular and in the extracellular solutions to block sodium/calcium exchange. Total cytosolic calcium flux during the transient was inferred from I-Ca, [Ca](SRT), [Ca](i), and cellular buffering characteristics. Fluxes via the calcium current (I-Ca), the SR calcium pump, and passive leak from the SR were evaluated to determine SR calcium release flux (J(rel)), Excitation-contraction (EC) coupling was characterized with respect to both gain (integral J(rel)/ integral /(Ca) and fractional SR calcium release. Both parameters were virtually zero for a small, but measurable [Ca](SRT). Gain and fractional SR calcium release increased steeply and nonlinearly with both [Ca](SRT) and [Ca](SR). We conclude that potentiation of EC coupling can be correlated with both [Ca](SRT) and [Ca](SR). While fractional SR calcium release was not linearly dependent upon [Ca](SR), intra-SR calcium may play a crucial role in regulating the SR calcium release process.