Ca2+ blinks measure the exit of Ca2+ from the junctional sarcoplasmic reticulum (JSR) in a cardiac myocyte during a Ca2+ spark. Here, the relationship between experimental blink fluorescence measurements and the [Ca2+] in the JSR is explored using long 3D simulations of diastolic Ca2+ release. For a fast intra-SR Ca2+-activated fluorophore such as Fluo-5N, we show that a simple mathematical formula relates the two for an ideal blink (i.e., when fluorescence signals come only from the JSR). The formula shows that normalized JSR [Ca2+] is much lower than the normalized fluorescence and that JSR Ca2+ depletes ∼40–50% more than previously inferred from blink fluorescence measurements. In addition, we show that stray fluorescence signals (e.g., from other parts of the sarcoplasmic reticulum network) can mask even deeper Ca2+ depletion. Overall, the simulations show that strong JSR Ca2+ depletion such as that seen in many simulations is consistent with the relatively moderate fluorescence changes seen in experiments.

中文翻译：

---

肌浆网的眨眼最低点测量值与强烈的局部 Ca2+ 耗竭一致


Ca2+ 眨眼测量 Ca2+ 火花期间心肌细胞交界肌浆网 （JSR） 的出口。在这里，使用舒张期 Ca2+ 释放的长 3D 模拟探讨了实验性眨眼荧光测量值与 JSR 中 [Ca2+] 之间的关系。对于快速 SR 内 Ca2 + 激活的荧光团，例如 Fluo-5N，我们表明一个简单的数学公式将两者联系起来以获得理想的闪烁（即，当荧光信号仅来自 JSR 时）。该公式显示，归一化 JSR [Ca2+] 远低于归一化荧光，并且 JSR Ca2+ 的消耗量比以前从眨眼荧光测量中推断出的要高出 ∼40-50%。此外，我们表明杂散荧光信号（例如，来自肌浆网网络的其他部分）可以掩盖更深的 Ca2 + 耗竭。总体而言，模拟表明，许多模拟中看到的强烈 JSR Ca2+ 消耗与实验中观察到的相对适中的荧光变化一致。